THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES CONFIDENTIAL Registe, N9 4090 Issued to . GUNNERY INSTRUCTIONS U. S. NAVY 1913 I WASHINGTON 1918 VD Navy Department, Washington, D. C, September 29, 1913. The following Gunnery Instructions, U. S. Navy, 1913. are approved and issued to the service. This volume was compiled in the olhce of the Director of Target Practice and Engineering Competitions. The Gunnery Instructions, 1905, forme,d a basis of compilation, which in- cluded a revision of such matter from the 1907 edition of Ship and Gun Drills as dealt with practical naval gunnery. In the preparation of this manual it was the aim to seek assistance from as many officers as it was possible and prac- ticable to reach; many officers contributed and collaborated, and reports of target practice were freely consulted. Finally, the manuscript was re,vised by the 1913 Board on Revision of Ship and Gun Drills, 1907. Particular attention is called to article 713, Naval Instruc- tions, 1913. regarding the care to be exercised with this publication. .JosEPHUS Daniels, Secretary of the Navy. 3 963721 CONTENTS. Articles. Pages. Chapter 1. — Handling men 1-21 7-11 Chaptek 2. — General principles of training. 22-30 12—14 Chapter 3. — General principles of naval gunnery 31-46 15-20 Chapter 4. — Details of training, individual guns 47-105 21-38 Chapter 5. — Training for collective gunfire. individual ships 10&-144 39-48 Chapter 6. — Training for collective fire, several ships 145-153 49-51 Chapter 7. — Torpedo defense 154-164 52-54 Chapter 8. — Torpedo training 165-209 55-75 Chapter 9.— Hints for turret officers 210-259 76-92 Chapter 10. — Hints for officers of a broad- side battery 260-282 93-100 Chapter 11. — Toi'pedo vessels and sub- marines 283-297 101-105 Chapter 12.— Notes ou target practice 298-300 106-110 Chapter 13. — Alignment of sights and bore sighting 301-326 111-129 Chapter 14.— Fire-control telephones 327-330 130-138 Chapter 15.— Range finders 337-342 139-143 Chapter 16.— Spotting 343-410 144-177 Chapter 17. — Problems in fire control and calibration 411-420 178-202 Chapter 18.— Station bills 421-427 203-209 Chapter 19.— Errors of gunfire 428-478 210-247 Chapter 20.— Rewards and scores 479-487 248-250 Chapter 21. — Gun pointers and turret and gun captains 488-509 251-260 Index 261-281 6 CHAPTER 1. HANDLING MEN. " Biatoricalljf, good men icith poor ships are better than poor men with good ships." — Mahan. 1. Importance of proper handling of men. — Of far greater importance to officers than any material or tools committed to their charge is the personnel with which they are con- cerned. The spirit and training of the men has always been a more important factor in winning battles than the charac- teristics of the ships or of the weapons employed. Success in training and in the cultivation of this spirit depends to a very considerable degree on success in handling men. 2. Self-training on the part of officers. — It is not fair to the ship or to the men under the control of an officer to make them bear the brunt of personal deficiencies existing because of a neglect of self-training, which is incumbent on all officers. If satisfactory results in handling a command do not appear to be forthcoming, an officer should make a study of himself, his methods, bearing, and attitude. The cause of the difficulty may be discovered. 3. Force of example. — Men will take just as much interest in their duties and work just as hard as the officers who are placed over them. Example appeals strongly to men, and officers must bear in mind that their bearing, manner, and language in dealing with seniors, as well as juniors, are all copied by their subordinates. An officer must at all times set an example of industry, zeal, initiative, and punctuality, as well as neatness of dress and correctness of bearing, if he is to expect these from his men. ' f . 8 GUNNERY INSTRUCTIONS. 4. Criticism of superiors. — Hostile criticism of authority will ruin any organization and completely destroy unity of action. A subordinate is seldom in a position to judge of tlie actions of his superiors intelligently and should not be prone to criticize until aware of all circumstances and facts. De- structive criticism whicli is born in officers' messes is con- tagious, and will soon spread through the ship and completely kill sliip spirit Cooperation is essential on the part of all hands. Each individual must be assured that his own part and task are thoroughly accomplished and in a way which will best assist others working toward the same end and while yielding unqualified support to authority. This is es- sential to success in any organzation, where many men are employed, as a fundamental of discipline. 5. First attributes of an officer. — Good manners, coolness, and self-control are the first attributes of an officer and are just as important in dealing with juniors as w'ith seniors. Leadership is an essential. It is fundamentally based on proved superiority. The officer must be first in everything at all times. 6. Importance of understanding individuals. — A most im- portant thing is to know men thoroughly, their peculiarities, abilities, weaknesses, character, etc. 7. Methods of handling men. — Praise will frequently better promote interest and efficiency than censure or punishment. Be strict, but not harsh. Remember that you are dealing with individuals as sensitive and jealous of their rights as yourself. Fairness and impartiality in dealing with them are essentials. But little good and often gi-eat evil is accomplished by unnecessary shouting. Nothing is more discouraging to an individual than the finding of fault with him when he Is using his best endeavors. 8. Impoilance of interesting men in work. — No one objects to useful work. Interest your men in what they are doing. Be sure that they understand what it is intended to accom- GUNNERY INSTRUCTIONS. 9 pllsli and why. At drill, when teaching certain details, ex- plain why these details are necessary. Point out the diffi- culties and the methods for overcoming them, 9. Suggestions from crew. — Never disregard, but welcome, the suggestions from your petty officers and men. Give all consideration, and if suggestions are not practicable explain v,hy. Such an attitude on the part of an officer will always lielp to promote and encourage a live and personal interest ii. tlieir work on tlie part of the crew, and frequently many helpful ideas will be offered. 10. Seizing opportunities. — Take full advantage of opportu- nities as they are presented. There is too much to be done to expect unlimited time to attend to all the details of train- ing and developn^ent separately. The best organization is not one in which a single individual directs all details. It must be such that sul)ordinate leaders are given specific tasks for llie accomplishment of which they are given the necessary au- thority and for which they are held rigidly responsible. The leader must organize his forces and arrange his program ac- cordingly, taking full advantage of every opportunity that occurs. Many of the complaints regarding lack of opportunity come from those who fail to recognize opportunities as they occur and do not fully avail themselves thereof. Facilities, conveniences, and opportunities are seldom the best, but be sure to make the most of such as are presented. 11. Petty oflacers, — Petty officers are indispensable assist- ants. They must be able to realize and to exercise their re- sponsibilities. Expect the same loyal support from them that you afford your superiors. Endeavor to handle the junior ratings of your division through their own petty officers, and train your junior ratings to obtain information and instruc- tion from ther own petty officers. 12. Smartness and cleanliness essential. — A division that 1:: smart in infantry, boat, and other drills is more apt to be smart in gunnery than one that is generally slack. Cleanll- 10 GUNNERY INSTETJCTIONS. ness of uniform, person, and of ship are all important. No one is proud of a dirty ship or a dirty shipmate. 13. Competition. — Stimulate competition by all legitimate means. Arouse a desire to beat the other fellow, but only by Jionest and fair means. Analyze and post all records and scores. 14. At quarters and drills. — At quarters set an example yourself in military form and manners and your division will imitate you. Do not hold men at "attention" longer than necessary ; but when the command is "attention," enforce it. 15. Inspections. — At daily inspection at quarters avoid arguing with or questioning the men while in ranks as to delinquencies in uniform. Make a mental note of each case and overhaul the man about it after quarters. The best form is to inspect your division without allowing yourself directly to address a man in ranks about deficiencies in his personal appearance. To call a man down in the presence of others about his personal appearance does not nourish his self- respect, which if destroyed ends his usefulness. 16. Particular care with, young men. — Many young men are discharged as undesirable or with bad-conduct discharges who might have been saved to the Navy had they had more official interest and encouragement bestowed on them by the division officer. Youngsters who are inclined to be shiftless require forethought on the division officer's part to keep them from delinquencies. The more a young man is inclined to be delinquent in petty matters the more often a cheering en- couragement will bear fruit. When a man is bracing up, commend him. 17. Commendation, censure, and reports. — Commendations might well be heard by others and when merited should be prompt. Censure should not be public. Reports of a trifling nature are undesirable. Never report a man unless there is ample and good reason for believing that he has intentionally committed an offense deserving of punishment. GUNNERY INSTRUCTIONS. 11 18. Giving commands. — Much depends on the manner in which a command is given. The voice and tone employed and method of expression are of importance, as well as the char- acter of the command. All uncertainty is to be avoided, and the manner should carry with it the impression that obedience is expected. Clearness to the person to whom the command is given is essential. No command should be given unless it can be obeyed, and when given it must be obeyed. The giving of unnecessary commands should be avoideil. 19. Comforts of men. — Carefully look out for the comforts of the men. The successful ship is the happy ship, and the men must feel that their ship is their home. The Navy owes every man reasonable comfort in a place to sit, to eat, and a billet that will afford a night's rest. Look out for these. Details, often trifling, in controlling the uniform, berthing, messing, and living arrangements may greatly contribute to their welfare and contentment. It is an essential part of an officer's duty to care for such details. On Saturday, Sunday, and holidays, and after working hours, initiate recreation for your division, such as sailing parties, swimming parties, and the like. 20. Avoidance of petty annoyances. — Guard your people from petty annoyances, such as interference with meal hours. If any are away at meal time, be sure they are provided for on their return. AVhen men have been exposed to bad weather or have had unusually hard work, as is not uncommonly neces- sary on board ship, be sure that their well-being is looked out for. 21. Importance of minor details. — These small matters have a great influence. Once the men of a ship realize that the officers have their interest at heart the success of the ship is assured. In no other way can a strong ship spirit be de- veloped, and a slight effort in this direction on the part of officers will accomplish great results. CHAPTER 2. GENERAL PRINCIPLES OF TRAINING. 22. Training for war, the first principle. — The first prin- ciple to remember in training is that war should be con- sidered a contingency that is liliely to occur with but little warning. A second is that the closer the training exercises in time of peace resemble the conditions to be expected in battle, the fewer will be the derangements and the less will become the influence of danger and of these derangements on the moral qualities of the crew. 23. Training- more important than material. — Unless the naval officer, in time of peace, devotes thought and study to the important feature of his profession — making the most out of his command, whatever it may be — he can not prepare him- self for the duties that will come to him in war. In times of peace it is natural for other matters, such as features of administration, material, and design to occupy first place in the minds of those who will be called upon in war to use weapons and ships. Preparations for war can not be ade- quately accomplished after hostilities have begun, and unless the training has been correct and sufficient the officer will, when called upon for a demonstration of his proficiency, find himself in the position of the indifferent workman who in- variably complains most bitterly of his tools. Sticcess tvill depend to a far greater degree on the spirit and morale of the personnel, and on the training and ability of all to eoordinate their efforts, than on any features of administration or mate- rial. The proper bearing and zealous efforts of every ofiicer 12 GITNNERY INSTRUCTIONS. 18 are directly reflected in the Interest and enthusiasm with which the crew carries on the liard work necessary on their part. The importance of retaining the interest of the men is sometimes not fully appreciated. The successful and happy ship is the one in which the men are encouraged to have a knowledge, interest, and pride in their work. These can only be aroused by intelligent and cheerful zeal on the part of all officers. 24. Character of system. — The system of training herein prescribed begins with the selection of the units of the gun crews and describes the training necessary to render each expert in his individual duties. The gun crew is then per- fected as a team, and when this is accomplished the training is for the development of the ship's battery as a whole, and finally for the collective fire of the batteries of more than one ship. 25. Utilization of the spirit of competition. — This require- ment is fundamental. The natural desire of one man to excel another in any test of skill is an incentive to thorough train- ing that may be regarded as the basis of all real success. However complete may be the .system or the apparatus, or however diligent and faithful the officer, unless the desire to excel is excited the result will be mediocre. Perfunctory training will never produce as good an oarsman as boat rac- ing. This spirit should be fostered and utilized in the daily drills by pitting individuals and crews against one another. t!are should be taken to avoid all questionable or unfair methods. 26. Final purpose of training. — The final purpose of com- petitive training, battle efficiency, must not be lost sight of. The competition is but the means to that end. What is de- sired is a state of efficiency or a condition which will enable a vessel to make a good score under any circumstances and not only under the peculiar conditions of a particular problem. 14 GUNNEEY INSTRTJCTIONS. 27. Permanence in stations. — The skill of the ship in gun- nery depends directly upon the skill of each officer and man ill his individual duties. Neither officers nor men can reach their maximum skill if they are frequently shifted from one station to another. Members of crews should, however, be exercised in stations other than those they habitually fill, in order that casualties lo personnel shall not silence the fire. 28. Casualties. — Any training that does not pi*epare for and fully anticipate casualties to both personnel and materiel is incomplete. It should be remembered that in preparing for casualties no methods or devices should be allowed that would not be practicable in action. Many casualties probable in battle can not be ordered at the times of target practice with- out introducing an element of danger or interfering with com- petitions. These must be prepared for at other times. 29. Service conditions on drill. — In conducting drill the regular battle system of communications should always be employed. Turrets should be closed as would be the case in service. The conditions during drill should be made harder than they would be at target practice and, if possible, as dif- ficult as would be the case in action. Then when unforeseen contingencies arise men and officers will be schooled in steadi- ness. Though dummy charges are used, the safety orders must be carefully observed. A carelessness on the part of officers, begotten by either ignorance or failure to appreciate their duties is immediately copied by the men. 30. Investigation of unsatisfactory performances. — An un-* satisfactory performance at drill should always be carefully investigated and the cause definitely determined and removed. CHAPTER 3. GENERAL PRINCIPLES OF NAVAL GUNNERY. 31. Final objective. — The final objective of all naval gun- nery training is the development of an ability to hit an enemy rapidly, at varying ranges, and under different conditions of sea, weather, and light. The subject is a broad and compre- hensive one. In its final stage the training becomes that of the fleet, and involves the development of units to the highest efficiency. 32. Final stage of training'. — The gunnery training in this final stage becomes closely me^-ged with tactical development, as it is not suflicient to have good weapons and to be able to use them at target practice, they must all be brought into action and maintained there properly. Unless a maximum of effective fire delivery with both guns and torpedoes is main- tained from each vessel of a force engaged in battle, the gun- nery training can not be said to have been complete. The different classes of ships must be so trained that they may all effectively operate together. PROFICIENCY WITH GUNS. (Fired individually). 33. First essential. — It is imperative that each ship be able to hit, with rapidity, a target under favorable conditions. To make this possible, when all guns are firing, it is necessary that the vessel be able to do so first with each individual gun firing singly, 15 16 GUNNEEY INSTRUCTIONS. 34. Analysis of principles. — An analysis of the principles of naval gunnery must therefore first reduce itself to an analysis of the principles involved in excellence, with the individual gun. 35. Excellence, how measured. — Excellence in gunfire is measured by rapidity of hitting. It is evident that however large a percentage of hits a gun may make, if these hits are not made with the greatest possible rapidity, the gun will have failed to attain its highest efficiency. Rapidity of fire with inaccurate pointing is useless and demoralizing, and en- tirely prevents control of the fire of the gun whe^n fired indi- Aidually, and makes impossible the successful control of a group of guns when fired collectively. The following may be regarded as the two essential elements of excellence in gun- fire: (A) Accuracy of fire; (B) Rapidity of fire. 36. (A) Accuracy of fire. — This depends upon : I. The accuracy of pointing. II. Satisfactory sight setting. III. Elimination or reduction of errors of gunfire as men- tioned in chapter 19. 37. I. The accuracy of pointing depends upon: 1. The skill of the individual pointer, which is developed by— (a) Continued practice at his own gun or type of gun with mechanical tai'gets, in port or at sea, when other methods are not available. (6) Using a check telescope at sea. (c) Firing with subcaliber. (d) Actual firing at target practice. 2. The condition in which the sight, the gun, the mount, and the various appurtenances which affect accurate shoot- ing are kept, together with the degree of excellence in their design and manufacture. Unless tiie design is sal isf actory, and unles^the gun, mount, sights, and accessories are maintained in such condition that the difficulties in aiming and firing are GUNNERY INSTETTCTIONS. V minimized, the accuracy of pointing will be affected. This ap- plies to the facility of operation, and to the proper functioning of each individual part. A neglected mount renders pointing difficult and hence conduces to inaccuracy. Neglected sights always invite failure. If they are out of adjustment they insure great dispersion and misses. If they are weak and liable to derangement, they may jar out of adjustment while firing is taking place and thus invite disaster. Neglected fir- ing connections, locks, etc., promote hangfires, misfires, or pro- long firing intervals, all of which militate against good point- ing and are serious hindrances to rapidity of hitting. 38. II. Satisfactory sig'ht setting depends upon: («) The adjustment of the sight. The sight must travel with the gun at all angles of elevation. Lost motion is al- most sure to appear in time in the older types of sights, and careful supervision and frequent checking up of the adjust- ment thereof are essential. (See chap. 13 on boresighting.) (b) The accuracy and precision of the orders given to the sight setter concerning the setting of sights. This depends upon (1) the accuracy with which the sight-bar range has been determined, which may be regarded as the most difficult problem in naval gunnery; (2) the arrangement and condition of the .system of communications, together with the skill with which it is used. (c) The promptness and precision with which these orders are obeyed. It is manifest that however perfect the gun, the mount, the crew, and the ammunition, unless the sights are correctly set, the projectile will certainly miss the target. Creat care must be exercised in the selection and training of sight setters, and the accuracy with which the setting of the sights is accomplished should be carefully checked up after, and. if possible, during each run at target practice. Whatever the form of firing, the sight setter's duty remains the same. It is to set the sight as accurately and as quickly 34776—18 2 18 GUNNERY INSTEITCTIONS. as possible, both laterally and in elevation, each time a new deflection or range is ordered. The pointer always aims at exactly the same place, and all errors are corrected by alter- ing the sights. 39. III. Elimination or reduction of errors of gunfire. — These eri-ors are discussed at length in chapter 19. 40. Uniformity of loading. — Precision of fire depends to a considerable degi'ee on the uniformity with which the opera- tions of loading are completed. In B. L. R. guns the shell must invariably be seated, the ignition ends of sections of the charge must be to the rear, and the Ignition end of the last section of the charge must be close to the mushroom face, 41. Necessity for elimination of errors. — It is manifest that as the ranges increase, and the danger spaces are dimin- ished, the necessity for reducing and, if possible, eliminating anything which may produce errors in the accuracy of gun- fire should be carefully investigated. To a considerable de- gree investigations along these lines are possible only at proving grounds, but officers afloat should carefully study all data which may have a bearing on these errors. Such data may be obtained from the Range Tables, and other ordnance pamphlets and works on ballistics. As these errors are re- duced, the possibilities of increasing the effective range are vastly increased. 42. (B) Rapidity of fire. — This depends upon : /. The rapidity of loading. II. The promptness with which the pointer fires after the gun is ready, or the firing signal has been given; or, briefly, rapidity of pointing, ///. The facility with ichich fire may be controlled. 43. I, Rapidity of loading with modern guns depends upon : (a) The rapidity with which each member of the gun crew performs his duty. ( b ) The precision with which each one performs his allotted portion of the drill. GUNNERY INSTRUCTIONS. 10 (c) The "team work;" that is, on each member of the ^n crew performing his duty at exactly tlie proper time and in exactly the proper sequence, and the elimination of interfer- ences between individuals of the crew. Accuracy and thoroughness in every detail are requisites to rapidity of loading. Eagerness for excessive rapidity may result in interference, confusion, and casualties that can be avoided only by precision in every movement. Certain of these delays, such as the raising of a burr, the jamming of a cartridge case, or the breaking of a powder bag may more seriously interfere with the rapidity of fire than the delibera- tion necessary to surely avoid them. 44. II. Rapidity of pointing, like accuracy of pointing, de- pends upon : (a) The skill of the pointer. (b) The condition of the material. A skillful pointer will, under ordinary conditions, keep a gun of intermediate or secondary caliber, on a modern gun mount installed in a vessel that is a good gun platform, practically continuously pointed at the target, provided the mount is maintained in a perfect condition. The gun is there- fore aimed and prepared to fire shortly after the instant the pointer is notified that the gun is " ready." If to this degree of skill of the pointer and excellence of mount is added a firing mechanism in such efficient condition that the gun will fire when the pointer presses the firing key, ignoring for the moment questions of fire control, the rapidity of aimed shots is made practically equal to the rapidity with which unaimed shots may be fired. So long as this degree of rapidity is possible with any gim, it is evident that any time which elapses between the word " ready " and the firing of the gun, when not firing on order or on salvo signals, is a loss. A lack of adequate rapidity of pointing may result in a failure to fire when the signal is given, which lessens materially the 20 GUNNEEY INSTRUCTIONS. fire delivery of the ship, on the efficiency of which depends the value of the vessel as a battle unit. It must be remem- bered that rapidity of pointing is never to be obtained by the sacrifice of accuracy. 45. III. Facility of fire control. — At sliort, measured ranges, when firing guns singly, the spotting of shots other than the first shot in a string should be unnecessary. At long ranges the delays incident to spotting are of greater moment, as the time of flight and intervals of time necessary for the spotter to decide on his correction and to have this correction appear on the sights, are all appreciable. Effort should be constant to lessen these delays. The above remarks refer to day firing. They apply, how- ever, equally well at night. Gunnery at night is further com- plicated by — (a) The necessity for illuminating the target. (6) The difficulties of properly controlling searchlights. (c) The annoyances incident to blast of guns and glare of lights, which are increased by the gases of discharge. (d) The difficulties incident to setting sights with artificial illumination and of worliing about the guns under unfavorable conditions of illumination. 46. Necessity for cooperation. — From the above it is ap- parent that skill in gunnery depends not upon the pointer alone, but upon every person participating in the practice — on the ship-control, fire-conti'ol, and searchlight-control parties, the division officer, the gun captain, pointers, the sight setter, and on each individual member of the gun crew. The great- est rapidity of hitting can be attained only by the united efforts of each person concerned, working in complete har- mony with every other member of the crew. A failure in the slightest detail, on the part of any one participant, may ma- terially reduce the rapidity of hitting, and thus nullify the greatest possible excellence on the part of others. CHAPTER 4. DETAILS OF TRAINING— INDIVIDUAL GUNS. 47. Ordnance pamphlets. — Attention is invited to the nu- luerous pamphlets published by the Bureau of Ordnance con- tuinirifr descriptions of material and methods of operation. 48. Ordnance Instructions. — Particular attention is called to Chapter 26, Ordnance Instructions, Navy Regulations, and Naval Instructions, 1913. These instructions must be under- stood by all officers in any way concerned with the ordnance outfit. 49. Selection of crew. — There are now sufficient trained men in the service so that it should be very seldom that a gun's crew has to be selected entirely from new hands. With men who have been in the service for some time their pre- vious experiences, service, gunnery, and torpedo records should be considered when assigning them to battle stations. 50. Stationing the gun crew. — The division oflicer should first select the gun captain and members of the gun-pointer group and then the others of the crew% taking into considera- tion mental and physical qualifications and the requirements of the respective stations. This first assignment is, of course, tentative and subject to change when qualifications are better known. Attention is invited to article 2501 (2) (3), Naval Instructions, regarding the selection of gun pointers and the stationing of gun captains and pointers. 51. Selection of gun captain. — The general requirements for a qualified gun captain are thorough practical knowledge of the gun, mount, and various appurtenances, also of the 21 22 OTJUNERir INSTEUCTIOFS. drill giin, and a sj'stem of training, together with the execu- tive ability to drill and command the crew. He should be a man of resource and quick action, for in battle he may be called upon to act upon his own responsibility. The man's executive ability and general intelligence should be given the greatest weight, as these, combined with zeal, will quickly develop the necessary knowledge. As a rule, petty officers, being initially a class selected for these qualities, will be the men best fitted for these positions. A seaman who is qualified for gun captain generally possesses the qualifications that entitle him to promotion to petty officer, third class. 52. Selection of gun pointers. — Men with the proper quali- fications may be trained as gun pointers quickly and easily. In selecting gun pointers, division officers should give weight to the man's ability to shoot straight, as indicated by his record with small arms, in connection with good eyesight, nerve, and a cool, nonexcitable disposition. The importance of these latte;- qualities may not appear in preliminary train- ing, but they are essential and should receive first considera- tion. Men whose nerve and physical training will withstand the exhaustive tests incident to battle are those to be desired. A man's rating, general knowledge, or executive ability should not be allowed to have weight in his selection as a gun pointer. 53. Selection of sight setter. — The requirement that the sight setter receive regular training and act as second pointer for turret guns necessitates that the same care be exercised ill the selection of candidates for this position as for pointers. 54. Expiration of enlistment. — An important point to be considered in connection with the selection of gun pointers is the expiration of the candidate's enlistment. A man who has already qualified as gun pointer will not be deprived of his position at the gun (and hence of his extra pay) on this ac- count alone, but, when practicable, no new man should be selected for training if the expiration of his enlistment will not permit him to serve as a gun pointer for at least one year GUNNERY INSTEUCTIONS. 23 after qualifying for that position. The longer a man has to serve, the greater his desirability as a pointer, other consid- erations being equal. After a practice each division officer should ascertain how many of his pointers will remain until the next practice, and immediately put men in ti-aining to replace those who will not be aboard. In several instances ships have been called upon to hold practice very shortly after commissioning, and have demonstrated that where intelligent effort was made in stationing and exercising crews creditable performances were quickly possible. 55. Spare set of pointers. — A spare set of pointers and sight setters will be kept in training for each gun at all times. 56. Bunching of shot. — The value of a pointer should be judged by, the way he bunches his shots. A man may show aptitude by bunching, while another may demonstrate by scattering his shots that he has not profited by training and is undesirable as a pointer. In forming his judgment the division office^ should be sure that the scattering of shots has not been due to inaccurate sight setting or to other causes. 57. Training pointer. — The training pointer occupies a most responsible and difficult position, and particular attention should be given to the development of men for this station. 58. Devices for training. — The following mechanical de- vices are used for training members of gun crews. Success attained with them depends to a considerable degree upon the accuracy with which the apparatus is installed: (1) The dotter. (2) The Morris tube. (3) The check telescoiie. (4) Subcaliber attachments. (5) The loading machine. Having developed skill individually, the following develops the skill of the crew as a whole: (6) Drill at gun. (7) Target practice. 24 aUUirEEY INSTEUCTI0N3. The individual function of tliese will be explained in the oi'der mentioned. This explanation is made in considerable detail for the benefit of inexperienced officers. 59. Features taught by training with mechanical tar- gets. — The following features of training gun-pointer groups are particularly developed with mechanical appliances : (a) Position of pointer at the gun. — Unless the pointer assumes an easy position at the gun the best results will not be forthcoming. Pointers will sometimes select cramped po- sitions, with wrong eye at the telescope, hands improperly placed on the elevating wheel, etc. All of these must be cor- rected. It may not be sufficient for the pointer to say that his position is the easiest for hwi. (ft) Continuous aim. — Continuous aim does not mean that the line of sight is necessarily held on the target during the comi^lete roll of the ship, but it means that the gun is held accurately pointed throughout the firing interval; that the wires are on the point of aim and not moving across it when the firing key is pressed. This is essential to accuracy when- ever a gun is fired from a rolling platform. The feature of maintaining the aim during the complete roll is an element affecting rapidity but not accuracy of fire. An expert pointer will usually hold the horizontal wire of intermediate and secondary guns on the target while the gun is being loaded, and will be ready to fire the moment he receives the signal. The necessity of attempting continuous aim must be impressetl upon all pointers, together with the difference between main- taining the aim during the complete roll and during the firing interval only. (c) Method of operating gun. — The elevating pointer of a turret gun, where it is necessary, should receive training in laying his gun in the loading position after each shot, so that he will do it instinctively, and then resume his position at the sight, ready (the moment gun is loaded) to pick up the target; the trainer maintains bis aim at all times. GUNNERY INSTRUCTIONS. 26 id) Sight setting. — Hitting is impossible unless the sight setting is accurate; rapidity of fire is also impossible without promptness in sight setting; hence, it is essential that careful attention be given this matter. In setting sights there should be no wasted effort or time due to the sight setter raising and then lowering the sight, and vice versa. The correction should always be started and completed in the direction in which it has been ofdered. When a correction to the sight has been accomplished it has been found advantageous at elementary practice to have the sight setter call out "set." In all exer- cises of the pointer group, sight setting and range transmitting should be practiced, and the sights should be changed without the knowledge of the pointer. (e) Joint training of members of the gun-pointer group. — In view of the fact that two men are required to point each broadside gun of 3-inch caliber and above, and three men constitute a set of pointers for a turret, it is important that these men receive as much practice as possible when working together. 60. Advantages of the mechanical devices. — Guns rigged with mechanical targets generally work with greater ease and nicety of movement than others. Several mechanical targets should be rigged for each caliber, and these should be shifted from one gun to another. In some cases the difference be- tween a mount which has had considerable mechanical target work and others is so great that the exercise loses much of its value when the trained pointer fires his own gun on which a mechanical target has not been rigged. In so far as prac- ticable, a pointer should receive all training at his own gun. It should be borne in mind that the continuous use of one gun for the dotter and mechanical targets will be apt to eventually produce lost motion in the gears. 61. Advantage of one device over another. — Officers gener- ally express a strong preference for one or another of the de- vices herein mentioned for training gun pointers. The strong 26 GinfNlEY INSTEUCTIONS. arguments that are heard in favor of each show conclusively that there are good reasons for the employment of all of these devices. There are many times, however, when one may be utilized to far greater advantage than another. The value of any of these methods depends on the intelligence with which it is used. DISADVANTAGES OF TRAINING WITH MECHANICAL APPLIANCES. 62. Pointers trained with mechanical appliances failing on target practice. — Some pointers who consistently make good scores with the Morris tube and dotter sometimes fail to make good scores at practice. This is due to a variety of reasons, and these should be carefully considered by the division officer in deciding whether or not the pointer should be continued in his position. These reasons may be enumerated as follows : 63. («) Mechanical targets do not test the nerve. — Skill in pointing consists in always, not sometimes, having the gun accurately pointed when fired. The pointer whose mind is oc- cupied with dread of the discharge will never succeed in mak- ing a good score when firing from an unsteady platform. (6) Mechanical targets do not test the obedience. — Im- plicit obedience in regard to the point of aim is essential to consistent hitting. The temptation for a pointer to aim at some other point than at the point designated, in order to cor- rect an error made in the preceding shot, is very great, and may not appear to a great extent in training. (c) Perfunctory training. — The training will become per- functory if the division officer does not exercise vigilance. Training with mechanical targets may be carried out in such a manner that the pointer may make excellent scores by firing "on the fly" ; that is, when the line of sight is moving more or less rapidly across the target. Good scores are made more GUNNERY INSTEUCTIONS 27 readily with mechanical appliances than with the gun, on ac- count of the shorter liring interval, and also because the mo- tion of the target can be easily anticipated. Pointers are very often assisted by a fixed background which acts as a plane of reference on which to estimate the motion of the target. (d) Regularity of motion. — A ship's motion in a seaway is irregular, whereas, pointers are sometimes trained with a mechanical target on which ingenuity has been expended to make motion uniform. The target is rarely moved in a man- ner which reproduces the motion of a ship. The loss in both ac- curacy and rapidity of fire is frequently due, not so much to the difficulty of the elevating pointer holding on, as to the fact that the irregular lurching motion interferes very greatly with the trainers. Mechanical targets should have separately operated training and elevating gear. Successive rolls should not be of the same amplitude. Yaw should become quick and irregular as the training progresses. At practice with mechanical tar- get no pointer should ever be allowed to fire when the target is steady at the end of the roll. The ship's period, both for roll and for pitch, should be carefully timed, and the period for the mechanical target established from the data obtained. The period for roll, for the mechanical target, should be less than that of the ship. Pointers should, if practicable, be trained to fire at all times during roll. (e) Failure to follow throug'li. — It is frequently the case that a pointer who practices successfully with mechanical tar- gets will, when firing, follow only until he wills to fire, and fail to follow throughout the firing interval, thus insurii^ a miss when there is any considerable motion. A delayed action in the firing circuit will assist to correct this fault. This delayed action should be variable. 64. Extreme accuracy in pointing. — Attention is again par- ticularly invited to the necessity for carefully training pointers to the highest possible degree of accuracy in pointing. Unless the pointers have been so trained that we can always rely 28 GUNNERY INSTEUCTIONS. upon them to hit within a small space when all of the condi- tions are known, it will be impossible to develop an accurate fire under battle conditions, where we may have to depend very largely upon the accuracy of the pointers to determine the most difficult of all of these conditions, viz, the sight-bar range of the enemy. 65. Besult of firing when not on. — The pointer should be made to realize that if ho fires when not exactly " on " and following, he will certainly miss, causing a delay until the gun is reloaded, and giving the spotter an incorrect impression. When the gun is finally reloaded it will then be in exactly the condition as it was before he fired. The pointer has, there- fore, lost the entire time required to load, aim, and fire one shot, not to mention having wasted the ammunition, and Interfered with fire control. 66. Necessity for skill with mechanical targets. — Until a man has acquired skill through practice with mechanical de- vices, there is little use in his attempting to fire from a rolling platform. Progress^ must be judged by results and not by the hours of training. Some men acquire expertuess quickly, while others soon show that it is a waste of time to attempt to train them as gun pointers. 67. Necessity for accurate mechanisms. — Accurate, quick work with mechanical targets is impossible with faultji mechanism ; division oflicers should devote the greatest atten- tion to eliminating the lost motion in their mounts and sights. Before attempting drill it is essential that the adjustments be exact. Gun should be weighted at breech in order to com- pensate for the absence of the weight of the projectile and charge. Otherwise undue load is thrown on the elevating gear, which results in wear, and the pointer may be im- properly instructed in the manipulation of his mount. (Plac- ing a projectile in the gun is sometimes an easy way to over- come this diflBculty.) GUNNERY INSTRUCTIONS. 29 68. Progressive training'. — The dotter and Morris tube are Intended to train men to a high degree of manual dexterity in handling tlieir guns. The motion given to the target should always be kept slightly in advance of the skill of the pointers until they have attained proficiency. It must, of course, be slow and regular in tlie beginning, but before a pointer is expert he should be able to make a good score on a target whose motion is both irregular and rapid. THE DOTTER. 69. Advantages of the dotter. — The advantages of the dot- ter as an instrument fur the training and practice of gun pointers are: (1) Training with it may be carried on at practically any time, especially in port (or at sea when check telescopes can not be used, see art. 77). (2) Small inaccuracies in aiming are made apparent be- cause of the size of the impression made by the dot. (3) If well designed and made, the instrument is exceed- ingly accurate. 70. Variety of design. — Because of the number and variety of designs, it is not deemed necessary to describe in detail the various types of dotters used on board ship. Some are some- what complicated in their details, and all require careful ad- justment and attention. 71. Delayed action. — Attention is invited to the desirability of so rigging the dotter as to cause it to delay firing after the key is pressed, which necessitates keeping " on " the target during the firing interval. THE MORRIS TUBE. 72. Function. — The Morris tube affords a ready mean.s oi exercising the pointer group. It is clieap* easily rigged, aud 80 GUNNERY INSTRUCTIONS. readily adjusted, but is not as refined an instrument as tlie dotter. If tlie rifle is properly mounted tlie siglit setter may be given drill as well as the pointers. 73. Design and rig. — While a diversity exists in the method of rigging, the diagram shows the essential features of the most common form. Briefly, the appliance consists of: (a) A miniature target carried on a target frame, E, at the muzzle of the gun, which is capable of both vertical and latei-al motion, while remaining always at approximately the same distance from the pointer's eye at the telescope, D. (6) A small rifle, B, is rigidly secured to the great gun, and in such a position that the axis of its bore and the line of sight of the great gun intersect at the miniature target. (c) A bullet stop, A, secured to the muzzle of the great gun. 74. Turret devices. — In turrets having sights mounted other- wise than on the trunnions of the gun the Morris tube rifle must move parallel to the line of the telescope. This some- what complicates the design of the device for turret mounts. 75. Essential features.— The following are essential fea- tures of a successful Morris-tube target: (1) Elimination of vibration. (2) Every part of the target frame, boom, weights, etc., should be heavy and substantial. Weight is essential in order to secure a steady motion. (3) The elevation and train of the target should be entirely independent of each other. (4) The guys should be so rove off that they will not cause a jerky, irregular motion. (5) The target should move very slightly for a considerable movement of the cranks, giving the vertical and horizontal motion. (G) The target sheets should be so secured as to minimize the effect of vibration caused by wind. CZT U'^ c-.-.-.j.v.'njW I 7[ /i / ! / / J H k H •71 The Morris-Tube Target. Key to lettering on sketch.— Letters .\ to I refer to Intermediate puns, and J to N to turret guns. A is the iron b x, or bullet stop: B, clamp for small rifle: D, teleseope-sicht: E, target frame; F, spar or boom carrying target; G, small pulley for boom topping lift: G', reel for boom topping fift: H-H, transverse i guys passing over pulleys, one to weicht I, the other to reel J; J', turret telescope ; K, bullet stop on turret guns: L, bands on the chase of turret guns tor securmg small rifle; M, small rifle mounted on turret guns; N, target Irame for turret gun. 82 GUNNERY INSTRUCTIONS. (7) The small rifle should be so rigged that the regular firing key of the gun may be used. (8) The rifle should be mounted so as to permit it being quickly moved, both in elevation and in azimuth, a certain definite amount in order to afford exercise for the sight setter. In this case the bullet stop must be large enough to catch bullets fired from any position of the small rifle, the motion of which should be limited by stops. Reports of target prac- tice show that one of the chief causes of poor shooting is that the sight setters had been instructed, but not sufficiently trained in their duties. (9) The electromagnet should be so fitted as to delay the fire by a variable amount after the firing key is pressed, in order to force the pointer to practice continuous aim. (10) The minature target should be about 25 per cent smaller than the smallest projections of the target which it is intended to represent. (11) The bore of the small rifle must be kept clean. THE CHECK TELESCOPE. 76. Advantages of check telescope. — The check telescope is a most excellent means of training and of discovering the abilities of gun pointers. The advantages of this method are that— (a) It may be utilized at .sea if ships are cruising in com- pany. (&) No special apparatus has to be rigged. (c) By ob.sei'ving the principles carefully a division officer should be able to find out fairly exactly the abilities of his pointers, and what he may reasonably expect them to do at t!irget practice before a shot is fired. 77. Check telescopes in connection with mechanical tar- gets.— Training at Morris tube and dotter may be regulated at will to simulate, to some degree, any desired condition of GUNNERY INSTRUCTIONS. 33 iiiotidii. Witli clicck-tficscope traiuiii;,', only tlio iiiolioii on a paitifular day is availal)l('. As on niauy days at sea flioro is l>ra«'ti<'ally no*inoiinn in liij^ ships, overy opportunity for roupli-watcr rjipfk-telesrope work sliould he taken .-idvantage of. Toloseoix's with chock oyepiocos are very valnai)lo when used together witli tlie dotter. r>y utilizing; the check sifiht lli<> division ollicei- is cnahied to watch and control the opera- tion of tli(> doKer. and to study the methods and progress of his i)oinlers. 78. Types of check telescope. — In the later ships the point- ers" telescojies ai'c jtrovided with eyepieces, to he used in ciiecking tlie jxtintei-'s w checks out, but this, however, can be adjusted in a very short time. It is important for the officer at the check tele- scope to be in easy coinnmnication with the pointer so that Ite may coach him. A flexible tube .should he so rigged that the officer may speak into one end of it while looking through the check telescope. The other end of the tube should be close 3477R — 1 s .3 34 GUNNERY INSTRUCTIONS. o and opposito the pointer's ear. A buzzer attached near the ,'heck telescope outside, and connected to tlie tiring key, an- lounces to the officer the instant when tlie trigger is pulhxl. iVhen tlie officer is in direct coniuiunication witli tlie pointers, as, for instance, wiien inside the turret, tlie voice tube is unnecessary. 80. Necessity for firing signal. — It is desiral)le to connect a bnzzi'r in the tiring circuit which the pointer sounds when coniiileting liis contact on tiring and wlicn pi'operiy laid on the target. Signals to tire .should be given at projjcr part of roll. When there is an excessive roll, it is not possible to be "on" at all times with pre.seut gear, but there will come a time of comparatively easy motion when the signal should be made. Signals should not be given at regular intervals of time and should not be given oftener than the time required to load the gun. The interval between stand-by and tire shouhl not lie constant. 81. Conducting exercise. — In conducting the training with check telescopes ves.sels should steam on parallel courses, each hoisting a target of predetermined size laid out in rectangles. The division otlicer. by carefully obsei'ving the work of his point(M-s and by assigning a detinit(» value to certain rectangles in the poin.ter's target, is able to assign definite scores to his men. Three officers should be present at tnri-et check t tele- scope drill. If this 'is not practicable, a reliable petty officer may perform the duties of an officer in checking up and scor- ing. Individual score cards should be kept for each man, the result of Ills .strings accurately recorded, and results, with a mark of efficiency, posted on the bulletin board. 82. Necessity for keeping scores. — By keeping scores care- fully, like batting avei'agt's, and by iiosting them on the bulle- tin boards, interest and competition are stimidated, and a very good ide.-! may be gained of th<' work of the pointers an(l what GUNNERY INSTRUCTIONS. 36 iii;iy 1»(> cxitcctcil of tlnMii willi tlic slil]) nilliii^' and pilcliiii;;' uikUt various (•(uiditidiis of sea and wontluT. SUBCALIBER PRACTICE. 8'i. Value of subcaliber practice. — Tliis iiiaclicc is ni' ^n-cal \alu(' al'tcr a (■crtaiii aiinuiul (if sl-cill in Hiiiiitiii.u' lias l)eeii al- taiiicd. If can-icd dut with iintraiii(>d pointers, it will l»c foinid (>r less maicriai JK'noHt tiian otlierwisc. Sulx-aiihcr is a nii'tliod supiiltMucnt al to and advanced beyond tiiose previ- ously desi-i-ilied. but. as mentioned al)ove. it is an essential pai't of battle training. Subcalibei- iurnisbes an a.^ency jier- mittinji- iiractically a dress rehearsal of a battle jiractiee. ex- oreisiiif;- siiindt aneousl.v the fire-control parties, sjiotters, si.ijht .setters, and oIIkm's concerned, as well as the .mm pointers. Casualties nia.\' be sinndati'd :ind drill made vvvy I'ealistic. This Jiractiee can be held al any time two oi- more shiiis find themselves to.i;ctlier al sea, practically without re.uard to weather or sjieed. 84. Necessity for accuracy in adjusting pieces. — A first essential in subcaliber work is Ibat the smaller jtieces sliould be accurately bore si,i;iited with the lai\i;er ones to which they ai'e attaclH'd. 85. Firing connections. — The subcaliber jiieces should be fii'eil by direct attacbmont to tlie ordinary fii-iiiir connection. If this is not jxissible, a reliable, (juick means of .uivin.u' tin' tirin.u' siu'nal to (he man lii'lnu' the piece slioidd be arran.i^ed. 86. Table for subcaliber. — The follo\vin.tc table siiow.s the ivin.ii'es iit which the an.i^les of fall of the l-iiounder correspond to thu.se of the larger pieces at 10,000 and at 1,800 yards. 36 GUNNERY INSTRUCTIONS. C'orre- Corre- (JllD. Range. Service Angle of spnndinp Reduced Angle of sponding I. V. fall l-poiindri I. V. fall l-pounder range. range. Yardu o / o f 14'745 10, 000 2,fi00 41 1 , 975 2,000 11 52 2,600 l.-}"/35 10. 000 2, 000 1.") 12 2, 9.50 2. 000 15 12 2. 950 12"/50 ■ 10,000 2,900 5 21 ■ 1,7.50 2,100 10 42 2,500 12"/1') 10,000 2,700 6 1.5 1,900 2, 100 10 42 2, .500 12"/4n 10, 000 2,400 S 04 2, 1.50 2,100 10 42 2. 500 10"/40 10, 000 2,700 fi 54 2, 000 2, 100 12 05 2, 650 8"/45 10, (K)0 2, 7r)0 7 50 2, 125 2. 100 13 52 2,800 S"/35 10, 000 2,100 13 52 2,800 2,100 13 52 2,800 14"/4") 1,800 2,600 48 600 2,000 22 825 13"A5 1,800 2, 000 1 26 850 2,000 26 850 i2'7r)0 1 , 800 2, 900 38 500 2, 100 14 7.50 I2'74r, 1 , 800 2, 700 45 575 2, 100 14 7.50 12'740 1 , 800 2.400 57 700 2, 100 14 7.50 1()'740 1 , soo 2, 700 45 600 2,100 16 77.5 8'74.5 1,800 2, 7.30 44 600 2, 100 18 SOO 8'735 1,800 2,100 1 1 IS SOO 2,100 18 800 THE DRILL GUN. 87. Function. — The drill f^un pei-forins four distinct func- tions : id) Physical training. — It i.s inlendod iiriniMrily a.s ;i nicnns of i>li.vsic;il triiininij; for tlie loaders of internieiliate guns, .so (jiat muscles and wind will he eciual to tlu> strain re- (luired in hattle. ( ') I Precision. — Incidentally it trains individuals to expert- ness in Ihe hest and quickest method of liandlin.ii' the ammu- nition and in loadin,i;. ((') Team work. — After the individual loaders are exi)ert it affords an excellent method of traininu- the .gun crew in pre- cision of movement and in the avoidance of interference, or in ■' team work " while loading. (d) Saves the gun. 88. Method of use. — In the primary training the shellnian is instructed how to hold the shell, how to place it in the GUNNERY INSTRUCTIONS. 37 lirct'cli, ;iii(l how host to utilize his strtMii,Mii in siioviii.L;' the pro.j(»('tiIo home. 89. Character of drill. — The slieiiiiiiiu. haviuj^ rtn-eived iiidl- vidiiiil iiistnictlon and traininfi in what may be termed " form," should then l)e exercised with tlie j^uu crew.s. In the besiiiinuy- strinf^s of 20 shell, tlie usual number loaded in a stiMiifi, may ]>i(»ve excessive; liowever, shorter strings do not p:ive tlie desired training' in endurance, without whicli rapidity will (UM-rease ai)precial)ly after a few rounds. In all exer- cises with the drill gun tlie time of loading the strings should be taken. 90. Importance of precision of movement in loading.- — Un- less sd-ict attention is given to the details of tlie drill of each individual shellman at tlie drill gun the desire for rapidity will cause Ihcni to neglect precision. Precision of movement must at all times be insisted upon; it will be obtained only by constant atteiitictii to (he details and in gradually eliminating small delays in tlie various oi)erations of loading. 91. Removing- burrs. — A small balf-rouml tile should be provided at the gun for the purpo.se of removing liurrs when tiring, and members of tlie crew must be previouHly instructed wlieiv to look for them and liow to carefully remove them witiioul damage to the breech mechanism. 92. Loading drill for turret guns. — The drill gun is inap- plicaiile to turret guns; hence for these the training must be olitained by loading the actual gun, using drill and target shell, dummy charges, and tired primers. 93. Drill shell. — The i.ssue of brass drill shell has been dis- continued, target shell being furnished in tlieir stead. These shell are furnislied with bands which may be removed if so desired. Siiars are fui-iiislied for both turret and broadside guns, which are used to iirevent .sliell dropping through the bore wlien the muzzle is depre.ssed, and also for liacking out shell wliieli may stick. 38 GUNNERY INSTRUCTIONS. 94. Dummy charges. ^ — Dummy powder charges filled with small pieces of hardwood, beans, or other similar material, should be used. In order to afford the necessary training and experience in loading, these dummies should be made to represent as nearly as possible, in weiglit, shape, size, and ilexibility. the actual charge. &5. Loading drill in connection with pointing exercises. — Ivoading drill in connection with Morris-tube and check- telescope training may be advantageously practiced. DRILL AT THE GUN. 96. Joint exercise of crew. — As the meml)ers of tlie gun crews become skilUul in their individual duties, the entire crew must be exercised at its own gun. After details have been trained independently, turret-guns crews, handling-room ci'ew.'^, annnunition passers, and all details concerned with tlie operation of the turret unit nuist be drilled and exercised together in their duties. 97. Lost motion in training gear. — It frequently happens that the lost motion in the training gear of guns of inter- metliate caliber is so great tliat in closing the breech the plug- man throws the pointer's aim off the target, thus delaying the (ire. This lost motion should be dimiuished as much as pos- sible, and the pointer should accust(?m himself to it by fre- quently requiring the plugman to open and close the breech plug after each shot at Morris-tube practice. The plugmau should be trained to close the plug with the least possible derangement to the train of the gun. 98. Necessity for giving accurate ranges. — Though for the purpose of instruction fictitious distances may be necessary in connection with the objects u.sed as a target, they should never be employed if their use can be avoided. The valuable power of judging distances comes and improves with practice, and officers should seek to improve their powers in this direction, as well as to instruct the men by estimating the correct dis- tance of the moving objects employed as targets. GUNNERY INSTRUCTIONS. 89 99. Point of aim. — The point of aim coiiiiminiciited to the «un pointers sliould be well defined and thoroughly under- stood by all concerned. Such a point is tlie intersection of the horizon and the stem or stern of the enemy. These points sliould he generally plainly visible to all guns. It is desirabU to standardize the point of aim, and in firing at ships, unless another point is designated, the intersection of the stem witll the water-line will be considered as the point of aim. Pointers nuist be carefully instructed not to fire wildly if they have losi the object, but in the case of firing at an enemy who is en slu-ouded in smoke the horizontal cross wire of the pointer's telescoiie can be kept on the horizon and the vertical wire kept on the center of the cloud of smoke, or on a mast if one is showing above the smoke. 100. Necessity for actually laying gun and setting sights. — When at drill, men must never be allowed to pretend to lay a gun. Correct sight setting is of the first importance, and accuracy in setting sights must be given great attention. 101. Gravity of mistake in target. — Ofiicers nuist bear in mind, and nuist impress upon the men, tlie gravity of the mis- take of aligning the sights of a gun on a wrong target. 102. Target practice — Function in the system of train- ing. — Target practi<-e at short rangt'S, while necessary to the tiiial development of a gun crew, must l»e regarded as a test (>{' the i)i-oficieiicy which has been atlaincd i-athcr llian as a iiictliod of training. It is a lurihixl diily in the sense that after a liiorongh ])relimiiiary training exiierience at actual firing is iie.cessary. It is quite possilile for crews which have received thorongh training to make a perfect score at their first elementary in-actice. Until target practice has been held the pointers and the memliers of the crew have not had the experience requisite for their assurance under service condi- tions. Division officers should take advantage of firing to note the men who become unduly excited, who appear gun- shy, etc., with a view to assigning thera to duty where failings 40 GUNNERY INSTRUCTIONS. will liuve tliQ It'u.st (letriuientiil effect. The tir.st elementary target practice after coimuissioiiing should be of great value in removing from the gun men who are so affected. E.special attention should be given to the demeanor of the pointers. 103. Elenmtary target practice. — Elementary target prac- tice is held at short ranges with screens of such size that all properly directed shots will hit. While the practice is pri- n;ari!y a le,st of the iioiutei's it also is a test of the entire gun's vi'vw and to a considerable degree measures the organi- zation and eihciency of the ship. .Spotters, other officers, and members of the crew are given experience and a practical demonstration of fire control in its simplest form. Material. c(^mnuinications. and efficiency of gun crews are tested under conditions more severe than is generally the case at longer ranges. 104. Development of elem^entary practice. — In the begin- ning of our modern developm^'Ut. and for some years, this form of practice was the only one in which ships competed, and it was held in smooth water. In order to assure otu'- selves of our abilitie.s. and to develop skill in loading, han- dling, and jiointing the, guns, antl to thoroughly test materials the conditions of elementary practice should be severe, liough-water conditions, which are not altogether possible with our present target e!|iiii)ment. are desirable. 105. Unsatisfactory performances. — The cause of every unsatisfactory i)erformance at target practice should be definitely detennin.t^d. Only by such invesrigatious may the sources of troul)le be discovered and elinnnated and i)rogress assured. L'urther ])rogress in gunnery depends, to a consid- erable degree, on the seeking out aiul elinunating of errors heretofore, perhaps, neglected as unimportant. Iidormation i'e,garding shots that miss the target is as important as that regarding those that hit, proviiled the amounts by which they miss are definitely ascertained and the causes of failures to hit determined. (See U. S. Navy Regs. 1913, art. 1G09 (b). CHAPTER 5. TRAINING FOR COLLECTIVE GUN FIRE— INDI- VIDUAL SHIP. The best protrition (ii/niDst on nirmti's fur /,s u ircll-ilirccti'd flic from I/our own f/iins. — Farra;iul. 106. Historical. — The history of \v:irs iii(lic:i!es tliat duds or fleet actions may begin at high ranges whifh may be re- duced l)e<-ause of the desire of one or t)0th antagonists to reach distances which will be " decisive." The manner of approach and the questiun of ranges can only be decided according to the conditions existing. 107. Character of training. — Gunnery training must l)e with the idea of making hits at all stages of an action, i. e.. (i) at the highest i-anges. (2) when the range is rapidly changing, and (3) when the range has been decreased. Casualties must be anticipated and demoralization avoided in any and all of what may become the phases of battle. 108. Protection afforded by well-directed fire. — jMucIi will depend upon the gaining of the "initial advantage." There can l)e no question of the superiority of the protection afforded by a "well-directed tire" at all stages of the battle. If sudiciently welt directed and sustained it will surely result in victory. 109. Collective gun fire (individual ship). — Excellence in individual gun lire having been attained, a consideration of the principles governing collective gun tire for a single ship follows. This becomes a question of utilizing to the best advantage a number of individually perfected gun crews, 41 42 GUNNERY INSTRUCTIONS. which resolves itself into the following: (1) Fire control ; (2) avoidance of interference of guns and interferences incidental to mixed calibers; (3) ability to sustain fire despite the casualtes which may be expected in action; (4) ammunition supply. 110. Necessity for coordination. — Success on the day of Wattle will not necessarily come to one who has good pointers, torpedo crew, or an excellent fire-control or ship-control party. All of these must he not only skilled individually but they must be so coordinated and schooled that they will operate together efficiently under any nr all of what then may become conditions. 111. Fire control. — This involves a knowledge of the sight- liar ranges, of the individual errors of gun and indices of powder, and the jironipt tran.smission of the range and battle ordeis to the battery. A sufficient supply of annnnnition to the guns and ability to sustain fire despite casualties and a liroi)er handling of the ship are also essentials to proper fire control. 112. Notes on spotting and fire control, published by tiie (leiiarlmeiu of ordnance and gunnery at the Naval Academy, c<»ntains a description of the apparatus and methods eni- jiioypd in llie fire conli-ol in l)attleslii](S at the present time. Wlule change and constant improvement may be expected in methods as material is develoi)ed the princi])les will remain the same. 113. The sig-ht-bar range. — A first e.sseutial to successful fire conti-ol is that the range finders, or means of discovering the range, .should be accurate and reliable. The errors of gunfire shoidd be reduced to a mininuun and allowed for in assigning the sight-bar ranges. This latter would probably be accomplished by firing trial or calibrating shots when expect- ing and preparing for a battle. In determining the ballistic corrections, the loss of velocity due to erosion as well as the GUNNERY INSTRUCTIONS. 43 cornH-tious for itMupeiiitui-c niid liei{,iit of hiiroiiK'ter should be considered. 114. Dispersion. — Proper fire control is inipossil)le if the dispt'i-siou is excessive. With excessive dispei-sions the spotter is helpless. A ]»roper iH-rceiita.i;e of shots may l)e Icept falling- in I'roiil i>t' tlie tar.t;el, ar.d l)ut few lilts made. If in sucii cases llic (Icllcction is ^iood and tlio dispersion is in i-an.i;e, the short siiols will obscure the otliers and nothiut;- definite can he de- termiueil by those cluirsied with tlie tire control regarding the ship's performance. 115. Point of impact. — It is fundamental that all pointers that ai-e under the same control xise tlie same iiolut of aim. which must Ix' well defined. 'I'lie iKiinl of aim may he con- sidered to lie llu- point at which the jMiinters lay their pieces. It should lit' distinginshed fi'dUi the point of Iniiiact, which is the point at which the projectiles fall. liy varying the range or ihe deflection on the sight, the iM)int of iini)act may l>e made to diffci' widely from the point rniedi:ite gmis is commenced, these must not !)(» a]h)wed (o sh)w or interfere with the fire of the major calibers. If a long firing interval is used for turrets, the intermediate guns may be fired between turret «alvos. otlierwise if short salvo intervals are used tliey should be lired together with the turret guns. 135. Individual control. — The training siiould permit the control of (he fire of l)roadside guns individually, as well as collectively, by night or day, and gun rnplains iind reliable I)etty officers, as well as division oHicers. nnist understand the methods to be followed in spotting and in fire control. 136. The spotter. — The spotter occupies a most important station, and much depends on the cool, good judgment of this officer, which must be developed by long experience and drill. He should know his range and ballistic data and must al.so have the heights and lateral distances between conspicuous points and other dimensions of his target fresh in his mind, that these may assist him to quickly find and hold the target. A spotter, in his training, should not lose sight of the differ- ences that will be presented in the methods necessary when fire is directed at a hull and not at a target screen. 137. Ability to sustain fire. — An ability to stand punish- ment is built into the ship in so far as practicable, and con- stant effort is being made to improve the defensive qualities of vessels. The deciding factors in coming naval battles, as 34776—18 4 50 GUNNERY INSTRTICTIONS. have been in those of the past, will be accuracy and volume of fire, which will only be insured by the morale of the men engaged. This morale, which will insure the fighting of the ship as long as she remains alloat, is unconquerable, will in- sure victory, and can be gained only by constant drill and preparation for action. AVhile the primary means and de- vices for supplying anununition and for directing guns should receive the greatest attention, the auxiliary devices and methods should not be overlooked. 138. Ammunition supply. — The question of ammunition supply in action should be carefully considered. The supply of sliell and powder from the magazine to the, gun. the opening of the boxes, and the disposal of tlie l)oxes and cases must all be provided for. It may frequently l)e possible to improve the chains of supply and to facilitate the careful handling of all classes of ammunition. It should be reme,mbereil th;it anniumitiou nuist not be permitted to accmnulate in exposed positions, as it then constitutes a serious source of danger. 139. Drill of amniunition crews. — There have been numer- ous instances at target practice where a turret crew, otherwise well drilled, failed to make a ci'editable performance because of a mistake on the part of the handling-room crew. The use of a wrong index may well cause misses that would result in disaster in action ns it has in failure at target practice. 140. Importance of minor details. — No detail of the drill and development of the fire-control, gun, and handling-room crews is .so slight as not to merit attrition. 141. Day individual practice. — The training of the col- lective tire of single ships is tested at individual ship prac- tice in so far as it is practicable to do so. With the present facilities we may measure performances at various ranges, but it is dilHcult to devise problems which will test the ability to make hits employing the entire battery, with a rapidly changing range. The ranges prescribed for day individual practices are long in orde.r that training may be with the GUNNERY INSTRUCTIONS. 61 view of sccuriii.u the " initial advaiitaf,'^ " and iu order to make condidons most severe. It must not hr assumed, how- ever, tliat it is necessarily the case that a battle of the future will l)e finally decided by a cauuqnade at lon.i: raii^e. The conditions of range can no( be foretold, anil Ir.aininR must antici|iale all of wlial may become the idiases of an engage- ni(>nt. 142. Casualties. — Casualti(>s are inlrodnced. as the outcome of battle may depend on tlie manner in which these are bandied as well as on the gunnery. 143. Artificiality. — Constant care should be exercised to a.void artificiality in any or all forms of lire coutrol, ship handling, or dealing with casualties. 144. Collection of data and analysis of results. — As im- ]ii'ovem(Mit ill gunnery is deiiende.nt on improvement in the precision of our guns as well as in control of lire, all data bearing tlierecui should be carefully collected at target prac- tice. The results of practices should be thoroughly an- alyzed. The time taken to get " on " the target after the order to " oi)en tire" is given, the "dispersion in salvos." and the "distance of the mean impact of salvos from the target" are all matters of importance in measuring a ship's performance at long-range practice as well as the number of shots hitting the target. CHAPTER 6. TRAINING FOR COLLECTIVE FIRE— SEVERAL SHIPS. 145. Collective gunfire (several ships). — The effective con- trol of tlie collective gunfire of sevei*al ships is impossible unless the battery of each ship can be handled efficiently. With this attained for vessels individually, the control of the fire of all may be accomplished. 146. Necessity for prearranged program. — When vessels fire collectively there is absolute necessity for a prearranged program of the order and methods of firing, etc., which is thoroughly understood by all officers concerned. The scheme by which the fire of vessels of a force is distributed should form an important part of the battle plan of a commander in chief. Once the general principles are understood and the methods worked out. the control of thfe fire of individual ships should be left in the hands of the captains, each of whom is in a position to be the judge of how his fire may be directed with the greatest effect. 147. Interferences with gunnery. — Signals and directions from outside sources during an engagement make for con- fusion. When fleets are locked in gunfire the one that persists with the least interruptions and interferences and compels its adversary to give way, maneuver, or modify its fire delivery, should win, other things being equal. There must always be loss of fire delivery due to rapid changes of course or speed or incidental to a shift of target. Prom a gunnery standpoint a ship is in position when she is able to make full, effective use of her battery, and does not interfere with the fire of other vessels in the formation. A methodical exactness of position and formation within reasonable limits is unneces- 52 GUNNERY INSTRUCTIONS 63 Kury to this end. Sudden attempts to gain or lose distance invite disaster, in tliat tliey may cause shots to miss that would otherwise be effective, and interferences may occur, such as the lifting of a safety valve, excessive smoke, or crowding: of another vessel. 148. Firing- at the wrong- target. — Results at target prac- tice make it appear that there is serious probability of a mis- take being made in the targets by a part of the battery of a tiring vessel. The likelihood of such mistakes would be en- hanced in battle if ships in the enemy's line were similar in appearance. A mistake of target by a turret or turrets would invite disaster, the likelihood of which must be fully appre- ciated, and the necessary precautions must be taken to avoid such an error. If a ship tire at a wrong target, one of the enemy's ships may be left not under fire, and the spotting of another ves.sel firing at liei- proper target wi ! l)e seriously interfered with. 149. Concentration. — When several ships concentrate on a single vessel, the ability of the latter to deliver an effective tire is disturbed by the fact that aside from the destructive effect of the enemy's shot, which rapidly lessens the effective- ness of her own fire delivery as well as reduces her defensive strength, she has several targets at which to direct her guns. Concentration should not be attempted unless all of the vessels of an enemy that may fire are covered. Conditions in the course of a battle may make one force of the two that began the engagement with equal numbers, temporarily, nu- merically the superior in vessels that may effectively utilize their batteries. On such an occasion concentration should be restored to. 150. Conditions permitting concentration. — For vessels to oont'entrate effectively at long range, it is necessary that they should fire in salvo. If a maximum of fire is to be delivered, these salvos should be from all the guns bearing. In other words, the maximum weight of metal should be delivered la 54 GUNNERY INSTEUCTIONS. each stUvo. By firing full salvos in rotation in tliis way sliips may identify and so control the fall of their own projectiles, and the target is cleared between salvos. As full salvos are necessary for effective concentration, it must then appear that conditions should permit successful salvo hring. Different parts of a long target may be taken as points of impact for tlie different vessels that are concentrating thereon. The pi-inciples and plan to be followed when concentration is to be employed should be thoroughly understood and form a well- understood part of the battle plan, and not left to be com- pleted after the battle has been begun. 151. Difficulties of collective fire. — In all collective fire, whetlier for one or several ships, the interference of smoke, blast, and the splash and explosion of shell may be expected. With fleets or divisions the difiiculties incidental to maneuver- ing may also be experienced. These may all be overcome by earnest effort and thorough preparation. It must be remem- bered that all the difficulties confronting us are also presented to our adversary, and the men and the fleet that have best trained for and anticipated the contingencies of battle will be the least disturbed thereby. 152. Division practice. — The training of the collective fire of several ships is tested in the various forms of division pi-actice that are prescribed. Effort is made to make these practices realistic, and they are varied from year to year in order to cover different phases and conditions. The weight given these forms of practice in the competition is low because of the difficulty of getting the exact scores of individual ships. It nuist n(»t l)e assumed, however, that the weights assigned determine the importance of these exercises, in which to some degree competition has been sacrificed to realism. These exercises are iierhaps the most important of the year as tests of the training of the battleships for war. 153. Battle Signal Book. — Attention is invited to the " De- velopment of gunfire " given in the Battle Signal Book, 1913. CHAPTER 7. TORPEDO DEFENSE. 154. Character of problem. — The problem of protecting capital ships aj^aiust the attack of torpedo vessels, under the various <'onditions which may be expected in war, is difficult and is one now giving all navies much concern. 155. Examples during' Russian Japanese War. — During the recent struggle hetween .lapan and Russia several of such attacks occurred and while widely different I'esults may be expected in the future, as a result of better training and ma- terial, the following figures are illuminating when considered in connection with the character of the personnel and the (.■t)nditions obtaining in the two navies then engaged in war. 156. First case — Attack on ships at anchor at night (Feb- ruary 8, 1904). — Ten boats attacked eight ships anchored off Tort Arthur. Attack was not anticipated. Nets were not rigged and preparations to defeat an attack were not in any sense adequate. Eighteen torpedoes were fired, and three hits were made on Tsesarevitch, Rctvizan, and Palluda. The Rus- sian gunfire was ineffective. No Japanese torpedo vessels were struck. 157. Second case — Attack on ships at anchor at night (June 23, 1904).— Fourteen destroyers and sixteen torpedo i)oats attacked ten ships anchored off Port Arthur. Nets were rigged and the attack was expected. About 60 torpedoes were fired and no hits were made. One destroyer and three torpedo boats were hit, and three men killed and five wounded by gunfire. 55 66 GUNNERY INSTRUCTIONS. 158. Third case — Attack on ships under way at night (August 10, 1904). — After scattering of Russian force in the battle of this date, tliree Russian ships, the Probeyda, Sevas- topol, and Fresvyct, all of which had been badly used in day action, were attacked by 17 destroyers and 21 torpedo boats. I'robably about 70 torpedoes were fired. No Russian ships were hit. Loss admitted by Japanese, nine killed on one destroyer that had been hit by two shells. One Japanese de- stroyer struck by a torpedo, losing one killed and eiglit wounded. This vessel was not sunk. 159. Figures approximate. — The above figures are given by a prominent British naval officer and writer, but may be only approximate. They indicate, however, that the difficulties in- cidental to torpedo attack at night are by no means confined to the battleship. In studying the question the point of view of the officer of the torpedo vessel, and of -the submarine, and of the difficulties to be encountered by them, must be considered. It may have been true to some degree that, in the cases cited, the shots that did not liit the torpedo craft, but came close, may have counted for the purposes of torpedo defense. 160. Rapidity and volume of fire. — In repelling an attack, full advantage should be taken of the rapidity and volume of fire permitted by the type of gun, the number of guns, and tlie ammunition supply, provided for the purpose. Casualties to material of course must be anticipated. 161. Identical methods impracticable in all ships. — Iden- tical methods will probably not be equally effective in all of the various types of vessels composing the fleet. Zone fire, which lias been recommended many times for torpedo de- fense, has not yet been given a practical test. The training should be with the idea of using to a maximum the battery and facilities for control, but the fact that the peace arrange- ments will be deranged and modifications of a necessity be introduced in service, should not be overlooked. GUNNERY INSTRUCTIONS. 67 162. Artificiality of practices.— All torpedo defense exer- cises must be to a considerable degree artificial, but in no form of exercise is it more necessary to avoid the false train- ing and artificialities practicable in peace and leading to in- correct deductions and plans for war, than in torpedo defense. 163. Concealment and searchlights. — p]ssentials for a bat- tleship are concealment, evasion, and change of course if there is likelihood of discovery. The occasion may arise, however, when searchlights will be required. Spotters, searchlight-control men, and pointers in such cases must all see the target. Noises and confusion must be absolutely elimi- nated. The beams of searchlights must be handled intelli- gently or more harm than good will result from their use. 164. Necessity for a program. — As in all other exercises, a definite, well-understood program is a first and last essential to success. Attention is invited to the type plan for torpedo defense, chapter 18. CHAPTER 8. TORPEDO TRAINING. 165. The end in view. — The pnipose of all torpedo training i.s the efficiency of the lorpedo buttery on the eve of war. This includes personnel and material, and may be otherwise stated as the problem of getting our torpedoes in contact with the enemy in the most effective way and under the peculiar conditions to be anticipated in war. Everything that is done in peace, e\ery daily task, small or large, should be subjected to this criterion. No matter how convenient or expeditious proposed methods may appear, they should be subordinated to the end in view. 166. Knowledge of material. — One of the greatest deter- rents to progress is a tendency on the part of personnel to simply follow general directions and to investigate only where troubles have forced investigations. Results obtained will lead to misdirected effort and erroneous conclusions when the users of material fail to equip themselves with detailed and thorough knowledge of the mechanisms with which they work. The starting point, therefore, on the part of officers is a thorough study and understanding of all the details of tlie mechanisms assigned to their charge. Through them the necessary knowledge must reach the enlisted personnel. It is important that no attempt should be made to get re.sults until this knowledge is first obtained. 167. Damage the result of inexperience. — The permanent damage done in a single day of experimentation by Inex- 58 GUNNERY INSTRUCTIONS. 69 perienced personnel has frequently exceeded that which, with proper care, should be expected during the entire normal life of the material. 168. Full advantage taken of opportunities. — The time which vessels can devote to torpedo tiring during a year is limited, therefore full advantage should be taken of all op- IHirtunities which are offered for practical instruction and exercise. 169. Coordination. — Successful operation of torpedoes re- quires cooperation and coordination; in other words, "team work " developed to a high degree of perfection. It is abso- lutely essential that every menil)er concerned in the prepara- tion of a torpedo and tube for firing should have a good under- standing of the duties of every other man, and that the neces- sary work involved shall be so systematized and organized that nothing will be left to chance. A single detail overlooked can easily ruin a performance or prove disastrous. Perma- nence In stations is desirable. 170. Instruction. — Tiie instruction of the personnel should commence as soon as the tentative assignments to stations have been made. Due to the lack of permanence in our en- listed personnel, a constant school of Instruction on board ship must of necessity be maintained. Courses of instruction should be laid out in detail in advance and executed as planned. After a reasonable time has been devoted to the in- struction, rigid and practical examinations of each man on subjects pertaining to his station should be conducted. 171. Sources of knowledge. — Stated in order of importance the following are available on all vessels for the acquirement of a knowledge of torpedoes : (a) Periodic publications of the department, viz, pamphlets, bulletins, correspondence, target practice reports. (b) Working drawings and descriptions. (c) The material itself. 60 GUNNERY INSTRUCTIONS. Some one must be responsible for the fact that a complete set of publications and working drawings are kept on hand, corrected to date and available for use. Too often this ques- tion is left to care for itself, and nothing is done until delays or troubles develop some specific detail which has been neglected. 172. Nomenclature and methods to be observed.^ — -A strict adlierence to the nomenclature and terms used in the instruc- tions, blue prints, pamphlets, etc., must be observed. The use of any names, terms, etc., other than those authorized are indicative of carelessness, and results in confusion and loss of time both on board ship and in official correspondence. The methods approved by proper authorities must be followed until modified or revoked. 173. Routines. — The following tentative routine for the crew of a battleship torpedo room is outlined as a guide : DAILY. Tiibes : /. Unseat sluice-gate valves. Just start off seat and close again quickly. Drain into bilges. 2. Open tube covers wide. 3. Sluice-gate valve must be closed, and the tube cover closed and locked before knocking off work and report made to torpedo officer. One of the chief gunner's mates must be present when this is done. (Note. — With the exception of the opening called for in liar. 1 above, the gate must always be kept closed and locked, and must never be unlocked without permission of the tor- pedo officer.) Torpedoes: 1. Keep all oil cups full at all times. 2. Turn over each torpedo by hand at least six revolutions. 3. Move vertical and horizontal rudders full throw at least six times. GUNNERY INSTRUCTIONS 61 WEEKLY. Tubes : 1. Run out spoi>ii slowly twice Mondays and Thurs- days, uiiloss other work prevents, and if so on lit her days, torpedo oflicer to be jireseut. 2. Thursdays, test out tiring circuit and systems of connnunication from conning tower. Compressors, Thursdays, turn over and run against a load, unless compressors have l)een running during the week. MONTHLY. Tubes: /. («)r after each practice.) Remove toggle gear. Clean and oil with sperm oil, neve.i' with vase- line or thick oil. Tori>edoes : /. Each torpedo to be run in aii' slowly for at least five minutes. All oil cups full. ,1. (Or after each practice.) Remove and in- spect gyro mechanism, and oil gear train through gyro door. Inspect gyros. The above indicates some of the points a routine sliould covcir. It is important to eliminate everything wliich is not to be carried out strictly in accordance with the letter of the rou- tine. The routine should be as brief and concise as possible and wi-itten in language wliich can not be misconstrued. 174. Torpedo officer's notebook. — It is important for the torptMlo ollicer to keep a notebook, not only for his own in- formation, but for that of his relief. The foil wing are sub- jects which should be covered in such a notebook: All orders, bills, instructions, etc., issued. Notes regarding pernuinent installations, such as tubes, air lines, accumulators, director and stand, etc. Lists of repairs and alterations recommended for navy-yard overhaul period with action taken thereon. 62 GUNNERY INSTRUCTIONS. Collatiou oi" causes of any abnormal torpedo performance, ami measures taken or suggested to remedy same. All data, correspondence or computations in connection with torpedo tlepartment whicli may be of future value, and there- by save duplication of work. All notes, opinions or conclusions from work or practice which nnght prove of value for future work. 175. Importance of records. — The importance of accurately and completely recording all available data and carefully collating san\e for every shot tired can not be overestimated. Tills especially applies to torpedo work on a battleship, where at best l)nt little torpedo practice can be expected. 176. Torpedo record books. — These should be kept carefully and accurately and shoidd furnish a complete history of each torpedo. They are the " service records " of the torpedoes and acc tlieory of tiro control nntl spotting should he explained, and the effects of inaccuracy of pointing demon- strated. JUNIOR DIVISION OFFICERS. 259. Suggestions for. — CJiven a well-organized turret di- vision, a lieutenant in command, you are ordered to this di- vision as jmuor oflicer. Upon joining ship, division officer ord(>rs yon to Candiarize yourself with the turret and crew as soon as possil>l<\ The turret officer may make, with you, a llioroimli insjiection of the turret, pointing out the general s.lienie of loading, the stowage of anununition, the parts or pl.Mces he has foniul needing particular care, and the assign- ment of vari((us ]>arts to the gunner's mates and their help- ers, i.jiy o\it a plan of study for yourself and stick to it so tar as your other duties permit. The following is an example of such a plan. Any one which completely covers the entire installation will he satisfactory. First day. — Go o\er the general arrangement of the turret, I 1 ) note method of sujtply of ammunition and (2) access to linndling room. Ci) draw a plan of magazines and shell rooms with positions of flooding and sprinkling valves on decks ahove. (4) examine barbette inside, noting which parts re- volve with turret and which are stationary, (5) note methods of securing turret for sea in order to tell at a glance whether turret is ready for training or not. (Wedges, center pins, etc.) Second day. — Examine turret turning mechanism ; where l)lace(l, how many sets of motors, where controlled, how shift from power to hand, how set up on friction gear (read pamph- lets descrihing the gear). 34776—18—7 98 GUNNERY INSTRUCTIONS. Gun-elevafiug mechanism, where placed, where controlLed and method of transmission of control, how shift from power to hand elevating, wliat the friction fiear is, and how set up, how balance a sun. i.- c.. whetiier when loaded with shell and drill charge, the gun is balanced and if not, why not (sub- caliber attachments may be in place). Examine trunnions and wed,t;"es. note whether ;j:uns are on knife edjj;es. Third day. — Sijilits and mechanism, routine <»f oiling: and cleaning the working parts. Mark of telescope, method of protection from dampness, how focus for dotter work, how shift sights when bore sighting. Fourth day. — Recoil mechanism; liow many cylinders, how many springs in each, principle of action, position of cylin- ders, how liquid is supplied. Amount of recoil, and how firing circuit and gas ejecting hose are fitted to allow for recoil. Fifth day. — Firing circuit. How many methods of tiring. how connected, what breaks in circuit and where, whether each pointer can fire his own or both guns and how this is accomplislied. Where motor generator is placed, where stor- age battery is secured, kind of battery and characteristics. How fire by percussion, what kind of primers are used, trace each lead of circuit, and note its use. Sixth day. — Brpecli nieclianism. Dismount and examine parts of mechanism, function of each, method of operation, safety devices, mushroom pad and rings, their object and method of adjustment. Note particularly the wedge of the lock and extractor and test a primer in tlie lock to see if it is possible to insert primer beyond extractor, and how avoid this. Seventh day. — Miscellaneous subjects : (a) Roller paths, condition of rollers; they nnist be free to revolve on pins. See nuts on holding down clips free of rust, path well greased. (5) Ventilating system. Where supply is obtained, and path of air circuits in handling room and turret. GUNNERY INSTRUCTIONS. 99 {!•) WIhmt (lr;iiiis lend (roii: l);n'l)('tt(' and linndling room. ( '/ ) .\(l.jus( iiiriit .111(1 (ipcnit ion of dotfcr .^r;ir. Thi.s can ho .stiKlicd host iit th'ill. (r) Soui'co of .supijly of coiniircsscd ;iir for ^iiis-o.jocting .sy.stoin, Mild loc.-itioii of accuiiiulalor and lead from il lo f:tii\s. (/) As opportunity offers, read ovor the battery log. uotinfr Ihi' miinher and kind of drills you can expect to have, the records of last hrinj:. scores made, any interruptions or acci- dents that oujiht to he avoi an ins])ection of the suhceiitral ( ,:,'et the elec- trician in ciiai-j;e of the plant to accomi)aiiy you). Find out how battle orders are commnnic-ited lo the turret. General arrangement of central, snhceiilral. and subs. chaptp:r 10. hints for officers of a broadside battery. 260. General. — Many of the remarks in the cliapter "Hints for tui-rei ofhrers " are pertinent for an officer assigned to a broadside battery. Tliis l)attery constitutes an important part of the armament of the ship. 261. Organization and drill. — Tlie organization and suc- cessful H(hninist ration and drill of a broadside battery, com- posed of guns frequently widely scattered, require the closest attention, and many ot1ic<'rs consider that it is a more difficult task tlian the development of a turret unit, where the crew and materia] are all closely as.sembled. 262. Material. — The details of the material assigtH>d the division nuist be thorouglily learned and every accessible part examined and put in order. 263. Lining up. — It is presupposed lliat llie guns have been pi-o])erly lined up and balanced when installed. The lining up may l)e checked when the shiji is in dry dock. Too much clearance l)etween trunnions and trunnion seats or cap squares may be taken up by screwing in on tlie wedges fitted for the purpose. Excess of clearance may be detected when the gun is being trained in either direction by suddenly reversing the direction of train. 264. Running in. — The guns should lie run in and the roller paths carefully examined for liaws. cracked rollers, etc. The recoil cylinders should be opened and cleaned and springs closely examined. 100 GUNNERY INSTRUCTIONS. 10. 265. Firing- circuits. — -In iiri'i'iii'in;;' ;;uii for lirin^,'. tlie elec- tric tiring' circuits should be Ihoroutfhly overhauled. Wipe off all connectlous with alcohol or gasoline to free them from dirt and j^rease, comiect up leads, and rinj,' through with a magneto. If circuit is found continuous, then connect a volt- meter in series, close lirst ou(^ tiring key then the other and note voltage given l)y both motor generator and battery; should be about 20 and 1(» respectively. As a tinal te.st fire a drill primer with each circuit, first seeing primer .seat wiped clear of greasq and oil. Tape all connections around breech to prevent possibility of grounds. 266. Friction disks. — Di.smount elevating-friction disks, wash with lye water, ;ind clean with silicon to remove all grea.se. Iieasseml)le and set up as taut as can be done by one m;in with a i;4-inch wrench. If this is not done the tendency of the muzzle to .iumji on lii-ing will throw the breech down. During tiring leave, the cover off the gear case and split pin out of the nut so that if friction disks slip they may be set up again without lo.ss of time. 'i'he training disks should be .set ui) to grip the arc tight enough to prevent siii)i)ing when the direction of train is re- \ersed suddenly. The niain precaution, liowever, should be to keep the arc at all times free, of oil or water. 267. Breech mechanisms. — Dismount and examine breech mechanism carefully. Examine gas check pad for cracks, smear well with tallow, and set up hand taut. Have a can of tallow at hand for this purpose during firing. See split rings turned with splits at opposite ends of diameter. See primer vent clear in wedge of firing lock. See that firing pins are sti-aight. imbroken, and clear of seat In wedge. 268. Gas-ejector system. -Turn air on gas ejector and ex- amine line for leaks. In.spect nozzles. Do not forget to re- move tompion before doing so. 269. Fire control.— The fire-control leads and devices must be uuderstood by the entire division. 102 GUNNERY INSTRUCTIONS. 270. Ammunition supply. — Tlie • aamuinition supply for Uiins is au iiiiiiorliiiit matter that should receive careful con- *ii(lerati()ii. There is a .^real deal of detail connected with the sup]»l,v of aiiiumiiiiioii. the (tpeninn' of cases, the disposal of boxes, wiping olf of cartridj^es, etc.. wiiicii will require prepa- ration and j;ood organization. 271. Selection of crew. — l<'or 7-inch guns the rammer men should he tall men. long armed, and of :iverage strength. First and second tray men should he good strong men. the strongest of the division, as the speed of the loading depends on them. Small men are best for ]irimer men. 272. Routine of drills. — To drill a large broadside battery the work must be mai)p;\l out ahead. One olMcer can not run the whole drill, each gun captain nuist do his i»art. The (httter and the drill gun should be made ready before quarters. When drill call sounds send the gun crews to the loading machine and the pointers to the dotter. One otticer takes the loading crews while another takes the pointers. 273. Detail of pointer drills — Mechanical target. — In the early stages all drill will be with the mechanical targets. l>etermine on the dotter cards the area which indii-ates a hit and mark all cards accordingly. It is not well to have the pointer tire too many shots at a time. .\ string of the ninn- ber of shots he will lire at practice is best. High-power glasses are trying to the eyes. lOorty shots for a pointer's morning work is enough, which means double that number when the time at the trainer's sight is considered. , If a bull's- eye is available make the pointers get well in the black. The target is oidy of such size that it will catch all shots aimed at the bull's-eye. In case of donltt coimt a miss. Use a buzzer attaclied to the tiring key and also have the pointer sing out "tire" to stimulate percussion tiring. Figure out all scores with meclianical targets or check sights and post the results on the bulletin board daily. Keep record in a book and average by week and month. Do not make the firing signal GUNNERY INSTRUCTIONS. 103 loo short !i) first. iM'ill llic li;ittt'i-y in hrojidsidc liriiiu l)y sciidiui; ii iii;iii to tli(> sul)si;iti<>ii. Let liiiii wear :i plioiio and l)e in conunnnication with a man on the aun (U'ck who will ;;ive the stand-l).v and tiriny sijjnal. 274. Cards for recording performances of gun pointers. — The following; tyiu's of cards have Ix-eii ustMJ with success, and are i-econuiiended l)y a jrunnery officer for la'cpiui,^ a record of the woi-k of pointers with tlie dotter : (Obverse.) Name SCORES MADE ON BECOBD STBINGS. Date. Score. Date. Score. Date. Score, [This side may be lillett in with pencil. 104 GUNNERY INSTRUCTIONS (Reverse.) GUNNERY RECORD CARD. Name, Rate, , Division, Gun, Station, Date of detail, Qualified as Date of expiration, Small arms qualification, Notes (Fill in this side with ink. St^ instniutious fur Iceepiugthese cards. Turn in to gunnery officer at end of weelc, and wlien completed. 1 GUNNERY INSTRUCTIONS, 106 Name.. Rate... TURRET DOTTER TARGET. i 1 1 Date - Full size Score. . C ] yards. of target , 30 t.y GO f. -et at 7,000 3 AND 6 INCH DOTTER TARGET. Name Hate Date n Score . White bull's-eye counts 5; black border 3; outside 0. Full size of target 15 by 15 feet at 2,000 yards. Elementary Practice, 191:5. C)l)taiti targets from armory. Enter score ou Guimery Record card and give target to pointer. Record strings must be fired under the e.vact standard conditions prescribed by the Gunnery Othcer. 106 GUNNERY INSTRUCTIONS. 3 AND 6 INCH DOTTER TARGET. n Full size of target, 21 by 15 by 25 at 4,000 yards. 275. Misfires, hangfires, safety precautions. — Triiin the tiring- pointer to he sure he ])re8ses both the motor generator and the battery tiring key before he calls " misfire." Train tlio gun captain to tii'e by percus.sion at the oi'der of the pointer. Train him to shift primers when all three methods have failed to fire the gun. Train the rest of crew to stand clear while i)rimer is being shifted. Train the crew never to open the breech of a loaded gun aftei' an attemi)t lias been made to fire it, without orders from tlie l)attery officer. ( See' Naval Instructions 1913, art. 2858.) 276. Loading drill. — The drill gnu nnist be used daily. I'rom 1<» to '20 loads ai"e enough. Reward the best crews by shortening the number of loads. Time each load from the order "load" until the i)lug is primed and closed. Average tiie times and post on the bidletin l)oard. After the loading drill, work the primer men witli their ])lugmen at the drill gun. l^et each jtrimer man place 2." to 50 primers daily. Im- press the crew th;it there is no danger and that they are as safe just beyond the linuts of the gun's recoil as anywhere in the comi)artment. I'articular attention must be given to the plugman. He nnist invariably comiiletely close the plug to avoid a misfire, and must stand and move in a way that will obviate interfei'ence with the loaders and at the same time clear the recoil of the gun. 277. Sight setting. — Send out ranges through the visuals and telephones. Have each sight setter at his own gun, and GUNNERY INSTRUCTIONS. 107 li.-ivc the uun i"ipl:iin rt'cmd cnrli liinjic mid dofU'ction us sot. I-'rrol)ah]<> tiring range to accustom tlio jMiintors to \vorliild .become accustomed to loading with guns in elevation. CHAPTEK 11. TORPEDO VESSELS AND SUBMARINES. 283. Essentials of training. — Tho general sy.steni ol' ti;iiii iii.i: oul lined in prevuuis cliapters (>l)taiiis Un- tliese ves.sels. Kssciitial iiKKlilications iiiiisl, however, l»e introduced in de- tails. 284. Artificiality of peace exercises. — Tlu> i)eace exereiyes given lo vessels of these classes partake, to a very considerable degree, of artiticiality IxM-anse of the absence, to some degree, in tlieni of the high tension and nervous strain, which will lie Ihe most ixitent factor in the oitei-ation of these craft and of their armaments in war. The ranges in practice for both gun and torpedoes are long, imjiosing some difficult i(\s. It is not intended that this training sliouhl teach that such are necessarily to be the I'anges for liattle. 285. Lessons of Russian-Japanese War. — A lesson of the recent struggle in the Far East is that generally an attack with torpedoes by the.se classes of vessels at night must be driven home, and th(> torpedo range must be one where hits (ire (iHHured. The development of the long-range torpedo will l)robal)ly give thes(> vessels a ]iew and wider role in future- day action. 286. Gun on destroyer. — While the torpedo is the ma.ioi* weapon of the tori)edo vessel the gun on the destroyer must not be neglected. We have numerous instances in war of the use of the destroyer for other purposes than that of defeating torpedo boats and of delivering torpedo attacks. Many oc- casions may be exi)ected to arise \^hen quick and accurate shooting will become necessary. 109 110 GUNNERY INSTRUCTIONS. 287. Destroyer actions. -'J'lir I'dllowiii.u .-irr cx^iiniilrs of re- tviit (h'slroyor ncl inns : On tlu' ni.nlit ol" iMjutIi !). 1!)04, four Russian and four Japanese destroyers enj^a^^ed in an intlecisive battle at short ranjie. One Japanese destroyer ^^•as not engaged. One re- l)ort(Ml 1 Icilled and 'A wounded, not seriously hit. Another re- ported 1 killed and 8 wounded, 2 guns disabled and speed re- duced. Another reportetl 5 killed and 2 wounded, 1 gun dis- abled and speed reduced. On March 10, during daylight, 4 Japanese destroyer^ en- countered 2 Russian craft, 1 of which was sunk. After this action 1 Japanese destroyer reported 27 liits, 1 killed, and 3 wounded. Another 6 hits, 1 killed, and 1 Avounded. Anotlier 7 or 8 hits, 1 killed, and 1 wounded. The fourth nil. 288. Independent control of guns. — l^>c("iuse of the exces- sive luolion of the destroyer the centralized control of fire, [tract iced in larger vessels, and which is desirable, may not always he jiossilile. Training should permit tlie independent control of giuis midi'i- the difliculties imposed by the poor gun platform, and the wide separation of the pieces. 289. Training' for individual control of guns. — I'articular attention should be given to the training of gun captains and jiointers in these ves.sels. Spotters must be trained who will be competent to independently control the tire of each gun (as is the case in larger vessels, sliould such become necessary), at the short distances which will jtroliahly become tlie battle ranges with guns. 290. Proficiency of pointers trained in larger vessels. — It may be that pointers of secondary guns who have received traiinng in larger vessels will not be well qualified to direct the pieces in smaller craft having an excessive and irregular motion. There should be no hesitancy in replacing such quali- fied ])ointers at any time by other men wliose fitness has been demonstrated. GUNNERY INSTRUCTIONS. Ill SUBMARINES. Hints and Suggestions for a Torpedo Officer of a Submarine. 291. Organization. — Tlio fonipleniciil of the pre-sent-day sulmiarine Ls 18 to 20 hhmi, of wliom are ^^uuuer'.s mates. Subuiaries carry from 2 to 4 torpedoes and should have 1 torpedo man for each tube. These torpedo men form the tor- pedo crew. 292. Torpedo firing. — Supiiose a toi'pedo has just been fued : Close the tprpedo-tiil)e cap, bh)\v or pump the tube diy. On deck rig the skids ; in the torpedo compartment, ri}i the cradle to the torpedo hatch. For holding and manipu- lalinj; the hitter, small doul)le tackles hooked to pad eyes are used. Six tackles, four to liold the cradle uii and two to move it rorc-aiid-aft, are ^.jeueraily employed. In some vessels the fcii'ward end of tlie cradlt> is held i)y an iron becket into wliicli a 1-t(iii ditVerential chain purchase is hooked. 293. Recovering torpedoes. — Special care should be given to till" e(iiupment and instruction of crews of boats employed in recovering torpedoes. The equipment shoulil include sufh- cient buiiys with ancliors. nose and tail lines, signal flags, pro- peller locks, etc. The instructions should include methos on (|uickly, necessity for keeping boat's propeller clear of torjiedo. jioint and manner of ilelivery alongside, and sig- nals to l)e employed. Tlie men of the tiring vessel slioukl be thoroughly instructed in the details of hoisting out the torpedo and striking it below. 394. To load and fire a torpedo submerged. — In order to put the torch pot into the exercise head, the torpedo must be pulled nearly clear of the tube. After the'torch pot has been inserted and cutter '.screwed on. the torpedo may be pushed back into the tube until only the immersion chamber and after- body are out. In this position the torpedo is charged and the 112 GUNNERY INSTEUCTIONC. JHljustments inaflo; tlie rap is, of course, closed at this time. U'iien ready. I'ani tlie torpedo lioiue, one man holding the tube- trii)pinK latrh up so that it will not catcli on the guide stud. \N hen the latter brings up against the stop the torpedo is home and seated. In order to he assured tliat the stop will lift readily when the torpedo is tired, tlie whole torpedo should he pulled to the rear about one-eighth of an inch. Next try out the impulse valve to see that it lifts. Then take off pro- l>eller lock and close the tube door. There are several schemes for flooding the tubes. Some officers obtain the trim of the vessel, then pump the tubes full from the water in the for- ward trinuning tank. This is considered the best way where there is time and water enough in the foi-ward ti-innning tank !<■ till tlie tubes, as it causes very little change in the weight and trim of the vessel. Other otticers prefer to flood the tubes which are not to tire, trim down, leaving .-i deficiency of about noo pounds in the forward trimming tank. When the run to- ward the target is nearly completed, open to cap and flood I lie tube to be tired. If accurately done this is a very good method, but there is always a chance of an error ))eing made ill tlie proper estimate of the trim, and when this occurs there is ditticulty in handling the vessel. Some other otticers flood all tubes at the beginning of the i-nn and obtain a perfect ti-im at the start. If the torpedo is absolutely tight this method is excellent, but the torpedo being in the water for per- hajis as much as half an hour, thei'e is .-iluays a chance that it will leak. .Tust before time to fire put a pressure of from 7r> to 90 pounds per sqnai-e inch in impulse tank and see that the hundred-pound tank to which the firing line connects has 100 iiounds pressure in it. In the I) and later classes the stop bar lifts antoyiatically from the guide stud, but in the C class and earlier ve.s.sels the stop bar Jias to be lifted by either a p(Hlal or a hand lever just before firing. 295. Care of torpedoes. — Owing to the very limited space for handling torpedoes in a submarine, they are necosxarily GUNNERY INSTRUCTIONS. H8 subjecled to auicli more severe usage than iu other vessels jind therefore need more care in order to obtain tlie best re- siilts. In times of peace only half the full complement of tor- pedoes is carried and these are stowed in the tubes. The tubes are always more oi" less dam]) and torpedoes must be hauled nut, \vi))ed olT. and oiled once a week, and before firing must be comj)lete,l.v brcjken down and reassembbnl in perfect condi- rion. After this final overlianl a torpedo sliould not be put in water until ready to tire. As it is necessaiw to flood all tubes ill order to open the f;\p and Are any one tube, tulies that are iiol to be tired sliould be empty. A subnuirine making an at- lack on a battleship or tleet of l)attlesliips would have all lier tul)e.s loaded with torjiedoes ready to tire ami would liave the remainder of her torpedoes ready fo load into the tubes when tli<' first were fired. This operation should not take long and would be accomplislavl as follows: ('lose the cap. blow the water out of the tubes tired, ojx'n the dooi's of tliese tulies, and load the torpedoes. When in a navy yard for a <'onsiderai)le slay, the torpedoes should be stored in a building and, before leaving the yard, .1.,'lven a thorough overhauling and test. 296. Care of g-yros. — The interior of a submarine is more or less damp at all limes, due to sweat, and s])ecial cai'e nuist be taken of the gyros to prevent rusting of bearings. The follow- ing methods have been used with good residts: (a) Fit either a locker or a tight box with felt-covered liedestals for the gj-ros and a socket for a 5-candlepower lamp. When the gyros are in place, turn on the light and leave the door or cover open slightly for an hour or two. until the air in the locker or box is dried, then close the cover and the gyrfis will be kept dry. {b) A copper tank is made and fitted with pedestals for gyros and then filled with sperm oil, in which the gyros are kept completely immersed. Before using, the oil must be 34776—18 8 114 GUNNERY INSTRUCTIONS. blown off the gyros with dry compressed air. Twice a year the gyros should be completely disassembled and all bearings cleaned, those in poor condition renewed, and all given a light oiling of wiitch oil. Before beginning torpedo work the gj-ros should bo adjusted in the stand. If opportunity offers, it is desirable, to check the adjustment by running the torpedoes over a range. A steady platform for adjusting in tlie stand may be obtained quickly by submerging to the bottom. 297. Tests. — The firing valves and tube mechanism should be tested frequently, and always before firing, and should be thoroughly overhauled while at a navv vard. CH AFTER 12. NOTES ON TARGET PRACTICE. 298. Preparations for target practice. — Target practice is ii test of i>revious trniiiinij; and prei»aratioii for i)atllo. and when the time for practice arrives it is too late to correct n(>j;lecte(l features. If tlie Iraininp; and preparations Imve l)('(>n tliorougli. everytlnn.u' sliould run sniootlily and all cas- ualties that occui- will ho handled witlioul confusion. 299. Suggestions for target practice. — Following ai'e cer- tain .suggestions for target practice — .some .apply to elemen- tary and others to battle practices, some to turret and others lo bri>adside guns. (a) MISCELLANEOUS. 1. A smart iit'rl'oi'mance is generally a good performance. Loss of time and a carelessness with details incidental to the practice militate against interest in the exercise and a satis- factory result thereof. 2. Arrange and publish a complete sequence of the practice. See that safety precautions, rules, and the orders for the prac- tice are understood by all concerned. 3. Be sure that pointers understand the theory of and i)rac- tical necessity for laying pieces accurately. 4. Tiike precaiitions to prevent noise and crowding in neigli- borliood of guns ; rope off space if necessary. 5. Sweep up decks about breech of guns. 115 lie GUNNERY INSTRUCTIONS. 6. Paint a circle around l^roadside guns at a distance from iireecli about inches greater tlian the recoil as a guide to the crew. 7. Be prepared for any casualties tliat may occtn-. 8. Designate and man substitute guns for each run. 9. Arrang(^ to care for observers and umpires that visit ship. (b) RANGE, TARGETS, ETC. 1. Measure and check size of target screens. 2. Give full instructions to repair party. 3. Arrange system of signals with repair boat. 4. Provide ample spare target gear. 5. See target screens correctly set. 6. Check speed and cour.se of target. 7. In coming on range be sure that ship has attained stand- ard speed and is steady on course before the firing point is reached. (c) FIRING CONNECTIONS. 1. Thoroughly test all connections. See that every connec- tion in the circuit is clean and secure and thoroughly tape them all. Use ether or alcohol in cleaning connections. 2. Overhaul firing keys. ( Instead of using a transfer switch many officers prefer to use the pistol grip on the motor gener- ator circuit and a push button secured to the side of the pistol grip in the battery circuit.) 3. Overhaul, clean, and oil the lock. Use oil sparingly around firing jiin and on face of wedge. 4. Clean and examine firing pin, and vulcanite bushings in electric firing locks. 5. Examine all wiring and insulation in firing circuits. 6. See that circuit will not be fouled or damaged by the recoil of the gun. If necessary trice up bight of wire by moderately strong spring to some point above gun. GUNNERY INSTRUCTIONS. 117 7. Test firing circuits witli volt and ammeter and finally with primers. 8. A missfire should not occur, hut anticipate and be pre- 1 tared for such a contingency. (d) AMMUNITION. J. Clean, brighten, and test all primers. 2. Clean all shell and cartridge cases. 3. Examine powder bags and repair any that may be dam- aged. (Place paper in eliamber of gun and then try a powder charge to be sure that the index to be used is in all respects satisfactory. See lacing is tight. Be sure that this charge is fired on the practice.) 4. AN'eigli shell and paint noses as directed; wet paint is slippery and may give trouble to and worry shellmen and ranmiermen. 5. Watch magazine temperatures carefully and have all powder temperatures the same when firing takes place. Have regard for powder temperatures if ammunition is to be left long on declv. 6. Test fixed ammunition by trying each cartridge in gun, fh-st removing firing pin. 7. lilxamine carefully for sunken primers (fixed ammuni- tion). 8. Be sure that charges will be loaded with ignition ends to (he rear. 1). See shell well seated and secure in cases (fixed ammuni- tion). ](>. S(^(' that shell bands are not burned and arrange to have slu'll uniformly and well seated in gun (separate am- nmnition). 11. Lay out shell and charges in a way most convenient for loaders. 118 GUNNERY INSTRUCTIONS, (e) MOUNT AND GUN. 1. Eliminate lost motion and see mount in perfect worliing condition. 2. See screw box free of burrs. 8. Overliaul and adjust gas checl< pad. 4. Overliaul, clean, and oil the plug, and all features of the plug operating mechanism. 5. See primer vent clean and primer seat clean and free of grit or dirt. G. Set up friction cones in training gear. 7. See electric-controller fingers smooth, and give same a light coating of vaseline. 8. Examine gas-expelling devices, blow through to get water and any possible dirt out of system, and see nozzles clear. 9. Examine and be sure that every nut, bolt, gland, etc., about the mount is in place and properly adjusted. 10. Fill the i-ecoil cylinders and see hlling plugs in and well set down. (f) SIGHTS. 1. Be sure that guns are correctly boresighted and that there is no parallax in telescopes, or parallax in the boresight- ing telescopes when the sight adjustment is made. 2. Be sure that sight scales are properly illuminated. 3. Be sure that sight setting will be accurately and expe- ditiously accomplished. 4. See strips properly secure and be sure that proper strip is in place for the charge and type of shell that are employed. Be prepared to wipe off sight lenses. 5. See that all clamps, etc., are .secure. Set up (aul befoi-e boresighting. and don't touch again before firing. G. Have ray lilters provided and ready for use. 7. When at navy yard test sights for parallelism, drift, de- flection, and adjustment with the guns, using battens, and eliminate lost motion. GUNNERY INSTRUCTIONS. 119 (g) FIRE CONTROL. 1. Arrange a (.leliiiile plan for tire conlrol, including firing of ranging shots, and salvos, and for individual turret control. 2. Prepare and check the necessary range data, ballistic and s]»()tting corrections, carefully. ;{. Test all iire-cuntrol circuits, tolephones, elc. 4. Be sure that there will be no pt)ssibility of u correction failing to reach or to appear on the sight of a firing gun be- fore the firing takes place. o. Adjust range finders. 6. If trial shots are allowed, get all data possible, including record of ability of turret officers to spot through periscopes. 7. See that suitable arrangements are made for spotter, searchlight-control men, those stationed to give salvo signals, etc. 8. Be assured that point of aim is understood by all pointers. 300. Frequent causes of poor scores. — Reports show that scores are most frequently reduced by the following causes: («) Slow and inaccurate sight setting. (h) Slow and uncertain communication of the spotter's ob- servations to the firing gun. (c) Too much spotting. With a correct rate of change of range after the spotter has brought the shots on the target they shouhl automatically stay there. There should be no necessity for spotting other than the first shot of a string. {d) Poor spotting. rmmediatehi alter practice check up sights, and search out the reason for any failure of material or unrntinfartorii per- formance. CHAPTER 13. ALIGNMENT OF SIGHTS AND BOEE SIGHTING. 301. Alignment of sights — Necessity for correct align- ment. — Sights shouUl always be in perfect alignment with the gun; that is, the axis of colliniation of the telescope should, when set at O and bore sighted at infinity, be parallel to the longitudinal axis of the gun at all positions of elevation and depressitin. In order to obtain such perfect alignment a high tlegree of excellence of sight installation is necessary and this alignment must be checked from time to time and adjust- ments must be made as required. The installation and align- ment of sights requires expert mechanical workmanship and a thoroiigh knowledge of the sight installation and it is not considei'ed advisable to attempt to realign sights, which are out of adjustment, except in case of absolute necessity, with the means available aboard ship. However, battery officers should know how to check the sight adjustments so as to be able to locate the source of any improper alignment and the resulting effects. Apparently inaccurate shooting, inconsist- ent dispersion, and other faults, sometimes attributed to poor gun pointing, may be caused by improper alignment of sights and by inaccurate bore sighting. If the sights are out of line, bore sighting will not correct the difficulty and with such the case, it is impossible to bore sight with accuracy. 302. Causes of error. — Any of the following causes may affect sight alignment: (o) Roller path not level. 120 GUNNERY INSTRUCTIONS. 121 (b) Guns not properly adjusted on the kuil'e edges, so that the trunnion axis is not parallel to the plane of the roller path. (c) Rigid parts of sight mount may be improperly installed. (d) Working i)arts of sight may be badly worn causing lost motion in some places and binding in others. Tlie battery officer is not concerned witli (a) for that is a defect which can not l)e readily ascertained, nor can it be easily corrected. Naturally, the amount of error depends upon the angle of inclination of the roller path, but whatever this angle may be, the sight alignment will be affected but little, if the trunnion axis is parallel to the roller path plane at any point in train. With guns independently pointed the error due to. («) can be neglected. 303. Checking' broadside sig'hts. — For checking broadside siglits the ship must be placed in dry-dock. If yoke sights are once properly installed, and are cared for, improper alignment will result from only the natural wear of working parts, and this cause of error will be very slight. 304. Checking' turret sights. — Tlie following procedures are reconnnended fur checking the alignment of turret sights. (See Ordnance Pamphlet No. 18 of September, 1907 — Notes on installation and tests of turrets, guns, and sights.) 305. Distant object method. — This method can be conven- iently aeconiplislied in dry tlock as follows: Adjust both gun- sight telescope and bore sight on a distant object. Elevate the sight to extreme range (without touching deflection) and then elevate the gun until the horizontal wire of the sight is again on the object observed. If the sight is in correct adjustment the vertical wire will also be on the object. If this is not the case, move in deflection until it is on and note the amount of knots error. By referring t(» the range tables the angular error can be obtained. If the error is one-half a knot or less it may be considered as satisfactory. 306. Batten method — (o) Train and secure turret. — The turret should be trained to its securing position either forward 122 GUNNERY INSTRUCTIONS. or aft where it cau be secured for several days while the sights are being checked. ( b ) Erect battens. — Procure five good pine boards 1 inch or li inches thick and 14 to 16 feet long, planed on one side. Erect these boards as far away from the sights as necessary for clear focus, with the smooth side of the boards facing the turret. The five l)oards must be parallel and in the same Itlane so that tlie axis of each telescope and gun prolonged will intersect the center of the board facing it. The boards must be well braced so that the completed structure will be absolutely rigid. Extreme care must be taken to insure that the face of the batten boards is parallel to the muzzles of the guns when they are level — in other words, parallel to a ver- tical plane passed through the axis of the trunnions. A step- ladder must be made so that work cau be done on the struc- ture without moiniting the battens, for to do so will cause the structure to change its shape and cause error. (c") Adjustment of knife edges. — Drawings in the posses- sion of the gunnery officer show the amount of necessary clearance around the trunnions when the guns are on their knife edges, and the knife edges must be adjusted to this clearance. The trunnion should be just lifted off its seat and most of tbe clearance should be left on the upper side of the trunnion. Some mounts are fitted with micrometer gauges to measure this clearance, but with others it will be necessary to use feelers. Before adjusting trunnion bearings the guns should be approximately level. ((7) Level guns. — The guns must be laid acciu-ately level. To do this, place the quadrant level on the gun or on the yoke in rear of the slide. Use hand elevating gear. (e) Set range strips.— See that all range strips and deflec- tion drums are tightly secured and set all sights accurately at zero range and deflection. (/) Adjust telescope. — Telescopes must be clean, free from parallax, and well secured in their holders and focussed. GUNNERY INSTRUCTIONS. 123 Cross wires must be exactly in place so that the vertical wire is actually vei'tical. (g) Adjust bore sights. — Put in the bore-sight telescopes and have them well secured. As the bore sights will be in place for some time, it is advisable to entirely remove the breech plug, rather than to lash it back on account of the sus- tained weight of the plug on the hiuge pin, which may affect the alignment of the rotating and swinging mechanism. Focus the bore-sight telescope on the batten boards after removing parallax. Put muzzle disks in place and adjust cross wires of bore-sight telescopes so as to split the central hole of the disk. Remove nmzzle disks. (h) Spot points on battens. — With guns level and using the bore-sight telescopes, spot points on batten boards ami through these points stre,tch a small strong waxed line horizontally as shown on Figure I. Likewise with pointer's and trainer's telescopes spot points (/, b, and c, respectively. Figure I. Through these points a, b, and c erect perpendiculars, using using strong waxed cord. These lines should be parallel and the distance x should be equal to x', and y should be equal to ?/'. Now if there be no turret structural defect and the guns are properly adjusted on the knife edges, they should elevate, in the vertical plane and the vertical wire of the bore- sight telescopes should split the lines a a'. Likewise if the sights are in perfect alignment with the guns, the vertical wire of the telescopes should split the lines b b' and c c' at all degrees of elevation. (i) Settling' of deck lugs.— With a ship that has been in commission for some time and has been through numerous targe,t practices, there is a certain inevitable settling of the deck lugs and turret structure. Though the guns may be properly adjusted on their knife edges, they may not elevate exactly in the vertical plane. After erecting the lines as mentioned above, elejvate the guns, having an observer sta- tioned at the bore sight; the displacement will at once be 124 eUWNERY INSTRUCTIONS. seen. After ascertaining that this condition exists, lay the guns level and again .spot the points a, b, and c. Elevate the guns to a point near the top of the hatte^i boards and spot Poinler's sighl Line. Left gun line. 1 p Trdtners sight Line. Right gun line Povnlcr's stqht Itne.. a-- 1-| 2 tlie points a', h', and c' ; through a a', h h' , and c a' stretch tight lines and proceed with the checking of the alignment of the sights. (/) Check results. — The guns should be elevated and de- pressed several times while the bore sight and sight telescope GUNNERY INSTRUCTIONS. 125 are checked over the lines to insure that they are correctly drawn. IMciisure the (lislance hetwoon eacli run's gun line and .sight lines, (-)n the battens this should be the same at toi) and bottom ; if nof. sights are not aligned with guu.s. 307. Lag in range. — To te.st for lag in range, due to binding and sitriugiiig of jiarls and to lost motion, set the sights accu- rately at any range, say ."i.OOO yards, and spot a mark on the batten board as shown a1 (/. Run the sight up to extreme range and back to 5,000 yards and see if the cro.ss wires split the mark fl : if there is lag. a new point (/' will be found. Kun the sights down to zero and back to ."i,000 yards as a further test. (See art. 305.) 308. Tabulation of results. — The following information is thus ascertained when checking sight alignment and should be carefully tabidated and recorded : id) Convergence or divergence of guns. (h) Perpendicularity of plane of elevation of guns. (c) Sight alignment. ((/) Lag of sights in range. 309. Parallelism. — Tram breech and nnizzle at level and at elevation of 5° to a.scertain the parallelism of the guns. It may be noted that exact parallelism is not essential, though desiral)le. A convergence or slight divergence at high ranges will not produce inaccurate results. It may not be possible to bring the guns exactly parallel or to any required degree of convergence, by trunnion bearing adjustment. This can be jiccomplished to a small extent, however, and once accom- plished the adjustment should never be changed without im- mediately realigning the sights. 310. Adjustment to be made by yard force. — Sight align- ment should not be attempted by the ship's force. The results of checking should be carefully recorded and forwarded to the Bureau of Ordnance for action, with a request that proper ad- justments be made, if such appear necessary. 126 GUNNERY INSTRUCTIONS. NOTES ON BORE SIGHTING. 311. Definition. — Bore ."lighting is the adjusting of gun sights, wlien the sight bar is set for zero range and the iiziniuth licad for zero deflection, so that the lines of sight of the pointing telescopes will intersect the geometrical axis of the bore produced at the mean range at which it is expected to fire. Guns that are correctly bore sighted for ranges of 10,000 yards are, for the purposes of battle, bore sighted for battle ranges. 312. Why necessary. — It is necessary because the line of sight does not coincide with the axis of the bore of a gun. 313. Errors due to sights not being in horizontal plane with axis of bore. — Fii-st, consider the error due to the sights being elevated above the axis of the bore. Figures Il(ffl) and Til (ft). It will be noticed that when the bore is centered upon a point Y at the target the lines of sight of the pointing telescopes will intersect the target in a liorizontal plane through the point X. a distance X-Y above Y, equal to the amount that the center line of the telescopes are above the center line of the bore. If the distance from the gun to the target is, for example 2,.')00 yards, the sight bar is set for 2.500 yards, and the gun GUNNERY INSTEUCTIONS. 127 > 128 GUNNERY INSTRUCTIONS. elevated so that the horizontal wires of the pointing telescopes are on the horizontal line through X, a shot Avould hit the tar- get at Y, not X. However, if the gun is centei'ed on the point Y and the sight Itar raiseroadside periscopic sight mounts and the periscopic sights for turrets wliich are attached to the trunnions of the guns. 314. Errors due to sights not being- in vertical plane of axis of bore. — Sighting errors due to the lines of .sight of the I)()inting and training telescopes not being in the same verti- cal plane as the axis of the bore is shown in Figures II (6) and III (b). In sight mounts Avhich contain both the elevating and train- ing telescopes the sighting error is the same for both tele- scopes, a.s.suming that the lines of sight are parallel to the GUNNERY INSTRUCTIONS. . 129 II /. 34776—18 9 Fia. II (6). 130 GUNNERY INSTRUCTIONS. bore. Therefore, iu order that the lines of sight be made to lay in the same vertical plane at the target as does the geometrical axis of the bore produced, it will be necessai-y to swing each telescope through a small horizontal angle a. 315. Uniform conditions when bore sighting.— Heat af- fects the droop of guns to some extent, and the atmospheric conditions vary at different times during the day. All guns of a battery should be bore sighted under similar conditions of temperature, light, etc., hence at as nearly as possible the same time of the day. 316. Turret trainer's sights. — In turret sight mounts where the training telescope is not connected with the elevating telescope, it is impossible to have the line of sight of the training telescope lie in the same vertical plane at the target as does the elevating telescopes, except where the target is at such a great distance that the axis of the bore and the lines of sight, if all parallel to one another, appear to meet and the horizontal angles through which the telescope should be swung are so small that the azimuth heads can not be moved a sufliciently small amount to correct them. If the target is to be at a short range, say 2,500 yards, and the turret sights are to be adjusted in azimuth, the sights may be adjusted to suit conditions as follows : Make each elevating pointer's telescopic line of sight inter- sect the geometrical axis of the bore of its gun at the target for zero' setting of the range and deflection scales, as shown in Figures IV (a) and (6). Then have the line of sight of the training telescope intersect the plane of the tai'get midway between C and D. It would be necessary for the training pointer to have a point of aim to the right of the bull's-eye for the left gun, and to the left of the bull's-eye for the right •gun, if guns are fired independently and the target is not of suflicient length to allow for the distance between the guns. 317. Preparation of bore sights. — The ship being at anchor, where there is no motion, anchors a raft or boat parallel to GUNNERY INSTRUCTIONS. 131 its own heading, and iu it erects a screen, preferably white with black horizontal and vertical lines. This screen should be spread as taut as possible, so that the top and side edges will be as nearly horizontal and vertical, respectively, as can be. If circumstances do not permit using a boat, then some prominent object, either ashpre or afloat and at the required distance, may be utilized. Bore sightiqg at night may be accomplished by using a searchlight to illuminate the target if the range is not too great. If the telescopes have been removed, before returning them carefully wipe the telescope holders to remove all grit from the bearing surfaces. Iu setting up the securing nuts on the holders, set up grad- ually upon each one in succession. Never set one screw or bolt of a bearing up taut and all the way home independently of the others. In setting up, never use any wrench other than the one supplied with the sight for this purpose, as the jaws of this wrench will give before the threads on the nuts will strip. After the telescope is in place the sight bar and the deflec- tion drum are moved through a complete throw to insure there being no freezing of parts. The breech plug is lashed back to prevent its accidently be- ing closed against the telescope in the breech disk. (This is mandatory. ) The breech disk is fastened or .screwed into the breech, and the bore-sight telescope secured in place, all parallax being removed. This telescope is focused after it has been screwed and clamped in place. When in focus the hole in the nmzzle disk will appear blurred. The muzzle disk (c') Figure II (a) has a hole about one-sixteenth of an inch in diameter in its center. Only the central hole should be used for centering the bore-sight telescope, the other four holes in the muzzle disk are for lighting purposes only. Before bore sighting, the GUNNERY INSTRUCTIONS. GUNNERY INSTRUCTIONS. 133 horizoutal wire of .ill telescopes slioukl be adjusted on tlie horizon or auy distant level object. In order to prevent in- jury or loss in centering it. a lanyard sliouhl be made fast to the dislv and the end passed in on dock or properly se- cured. To adjust tlu' breech telescope, there are four adjusting- screws on the holder for the" telescope so that by coming up on one and setting up on the one diametrically opposite, the telescope may be moved about until the intersection of the cress wires appears in the small hole in the center of the muzzle disk. These adjusting screws nuist not be set ui» so hard as to strain or distort the telescope, and only sufficiently to hold the telescope propei-ly in place. In looking through the bore- sight telescope, care nuist be taken not to disturb the adjust- ment by touching it with the hand, cap visor, or forehead. In case there is not sufficient light to see the cross wires of the breech telescope when the muzzle disk is in, a small port- able may be held near the muzzle. The muzzle disk is rotated through 180° as a check as to whether or not the intersection of the cross wires is centered. If it is found not to be, the fault is probably due to the muzzle disk not having been placed squarely in the muzzle. 318. Information in regard to the bore-sight telescope. — On pages 4 and 5 illustrated by plate 2 of Ordnance pamphlet No. 345 are a few words regarding the bore-sight telescope. On pages 7, 8, 9, 10, and 11 are some general notes on the care and handling and cleaning of telescopes which apply to a certain extent to the bore-sight telescopes. There are two sources of error in bore-sight telescopes which, it is believed, are very frequent, and are caused by disassembling the tele- scopes for cleaning. One of these errors is due to the fact that after cleaning the cross-line diaphragm and replacing it, it Is not returned to its correct position, resulting in a parallax, which causes an increasing error depending upon the distance 134 GUNNERY INSTRUCTIONS. of the cross-line diapliragm from the focal or image plane of the objective. All telescopes, if disassembled for cleaning, upon reassembling should be tested for this error by accurately focusing the telescope upon a distant object and moving the cross lines back and forth until no parallax remains. This, of course, will have to be done before the breech piece socket (57) and the outside adjusting tube (69) are replaced on the tele- scope. The second error is caused by the fact that in reassembling, the cross-line intersection is not accurately placed in the line of collimation of the telescope. To overcome this error, after the parallax has been eliminated as indicated above, the telescope should be placed in Y bearings and rotated. A turned surface is provided near the two ends of the telescope tube for this purpose. The telescope should be sighted upon a distant object, and it will be found that when the telescope is rotated in the Y's that the cross lines will shift upon the distant ob- ject. The cross lines should be accurately centered by means of the four cross-line adjusting screws (27) until the cross- line intersection does not shift upon the target when the tele- scope itself is rotated. In many cases it will be seen that the whole field of view moves up and down and from side to side as the telescope is rotated, but this is immaterial ; the whole point to be gained is so to adjust the cross lines that the inter- section itself remains steadily upon the same distant spot through a rotation of the telescope of 360°. When bore sighting on battens or at short distances there will be parallax in all bore sights. This can be best mini- mized by placing over the eye lens of the telescope a paper disk with a very small hole in the exact center. This centers the eye at one spot and eliminates the greater part of the error which would be caused by the parallax. All telescopes when received aboard ship are supposed to have been accurately adjusted and the two sources of error pointed out above are eliminated. Their adjustments should, GUNNERY INSTRUCTIONS. 136 however, 1)0 checked. It hus been louiid Uuit, owing to di.s- ji.*j.senibling for cleaning purposes or other causes aboard ship, all telescopes returned to the guu factory for overhaul and repair or sent to the fleet repair ship for repairs have been out of adjustment, due to one or both of the above-described causes. The obvious remedy is that these telescopes should not be disassembled for cleaning purposes aboard ship. If necessary to have them overhauled, they should be sent to the repair ship for cleaning and adjustment. A new bore-sight telescope now in contemplation is so de- signed that tlie bad features of the present bore-sight tele- scope will be eliminated. It is expected that this new bore- sight telescope will be furnished to all ships now under con- struction, and that it will, in time, replace the bore-sight tele- s(!bpes now in use abojird ships in commission. 319. Inverting bore-sight telescope. — With the present de- sign of bore-sight telescope, it is not practicable to invert the cross wires (turn them tln-ough ISO") in order to check for error, as it necessitates a loosening of the parts of the tele- scope, thus destroying adjustments already made. A new l)ore-sight telescope has been designed, but not yet adopted, which provides for inverting the cross wires in order to check the setting. At present it is necessary to invert the muzzle disk as a check on the centering of the bore-sight telescope as described in article 317. 320. Method of bore sighting. — Three persons, generally the division officer and two junior officers, do the work, at the same time utilizing the pointers to verify the results. (It is always well to have the pointers check the bore sighting of their gun, for then they can not attribute erratic shooting to poor bore sighting.) Frequently ships have a regular " bore-sighting board " composed of the gunnery officer and two division officers. This board makes a final check of all guns that have been bore sighted. The value of this scheme is readily seen. 136 GUNNERY INSTRUCTIONS. Ill making the adjiisluients. one officer is statioued at the l)reech telescope, one at the elevating telescope, and the other at the training telescope. It must be remembered that with yoke sights, a movement of the pivot bar moves both telescopes so that it is necessary to have an independent means of adjusting one of them. This adjustment is accomplished by two tangent screws with clamp bolts, placed under the holder of the training telescope. The pointing (elevating) telescope is adjusted by the sight bar and azimuth head. It is necessary to make the first adjustment on the elevating telescope and then the training telescopic adjustment. Either the horizontal or the vertical wires of telescopes may be ad- justed first. For example, the officer at the breech coaches in elevation and train until his horizontal wire rests upon, say, the top edge of the target when he calls out " Mark ! Mark ! " so long as the horizontal wire of the breech telescope remains in that position. The man at the elevating telescope notes how much his horizontal wire is off, and by moving the sight bar brings this wire " on " to coincide with that of the breech telescope. In the meantime the observer at the training tele- scope notes how much his horizontal wire is ofE and after the elevating pointer has made his adjustment the trainer brings his " on " by means of the tangent screw under the telescope holder, so that when it is adjusted all three horizontal wires will be " on " at the same time. The three observers change places and check. The same procedure is carried out for the adjustment of the vertical wires. The man at the breech coaches the trainer, calling out "Mark ! Mark !" so long as the vertical wire of the bore-sight telescope remains "on." The elevating pointer notes how much the vertical wire of the elevating pointer's tele- scope is "ofE" when that of the breech telescope is "on" and by moving the azimuth head brings it "on." In so doing he GUNNERY INSTRUCTIONS. 187 necessarily moves the vertical wire of the training telescope through the same angle, so that the man at the training tele- scope will have to wait to make his adjustment until after the elevating telescope is adjusted. The trainer makes this adjustment by using the tangent screw at the side of the training telescope holder and secures the holder with the clamp bolt. All observers change places and check results. In bore sighting broadside guns that are equipped with Iieavy periscopic telescopes that are seldom removed from the holders there are no tangent screws on the holders for sep- arate adjustment of the trainer's sight, and in lieu thereof the cross wires of the telescopes can be independently ad- justed by moving them in their vertical plane. The cross wires may also be rotated around their intersection as a center so as to make them absolutely vertical and horizontal. Each wire may also independently be moved at right angles to the line of sight without moving the other. In guns equipped with this type of telescope the elevating pointer's wires are brought "on" as with other types (al- though this can be done by moving the cross wires), but the training pointer must be brought "on" by moving the cross wires of the training telescope. 321. Adjustment of the sight scales. — Without moving the sight bar or azimuth head, the clamp screw, securing the range strip to the sight bar, is loosened and the range strip moved up or down until its zero graduation is opposite the reference mark on the sight-bar bracket. The clamp screw is then set up and the range strip secured. The dial of the multiplying range scale is then removed, cleansed of all oil, and the holder and back of strip washed off with lye water. This is to prevent the dial from turning in the holder when tke gun is fired. As an extra precaution against turning, a piece of emery paper may be cut to shape and placed between the dial nnd the holder. Some sights ai'e 138 GUNNERY INSTRUCTIONS. so constructed that instead of moving the dial tlie zero mark on the holder may be adjusted. The friction clutch on the azimuth drum is loosened, and the drum rotated until the "50" mark is under the pointer on the azimuth hend when it is then secured. In some sights the pointer may be moved l)y tangent screws to its position over the zero mark on the drum. The muzzle disk is now again placed in the muzzle so as to check up and make certain that the telescope in the breech disk has not been accidentally deranged during the bore sighting. Very often the square marks on the reference pointers for both range and deflection scales are very dim. This may be remedied by rubbing a small quantity of white paint over the mark engi-aved upon the pointers, and then wiping off all except that which has settled into the engraving. Before removing the bore-sight telescope, move the sight bar and azimuth head away from zero, then return to the zero readings again. Now observe whether or not the cross wires of all three telescopes intersect at the target. If they do not it is an indication of lost motion in the scales or binding of parts. This error should not be greater than 4 inches on a target 1,450 yards distant, in sights that have micrometer at- tachments, but it should be inappreciable in direct reading sights. 322. After bore sighting. — Remove breech telescope and breech disk and return them to proper custodian. Cover the pointing telescopes with flannel covers. (If circular pieces of blotting paper are inserted inside the dust caps it will be found that they aid greatly in preventing moisture collecting upon the object lenses.) A sign, such as "hands off," or "this gun has been hore sighted" will prevent thoughtless men from tampering with the sights. GUNNERY INSTRUCTIONS. 189 The peep sights carried alongside the telescope in holders slioidd be horo sighted after adjusting the telescopes. This is accomplished in the .same manner as for the telescopes, ex- cept that both the elevating and ti*aining sights are brought ■on" by moving the cross wires in their respective holders. 323. Turret bore sig'hting'. — The bore sighting of turret gun>< follows the general plan previously described for broad- side guns. Before adjusting, the parallelogram of parallel- motion sights should always be carefully tested. This is done, first, by raising and lowering the sight bar and being assured llial the sight mechanism is in proper working order, by l)lariginal type C telephone re- ceivers multiple connected. to all turret (iflicers" teh'phones. There are. therefore, fewer type CP telei)hones supplied than any otlier. (c) Tijpe CS telephone consists of the microphone receivers of the type C telephone, with tJie addition of a tran.smitter which is ///. .series- with tlie receivers. 1'liis teIei)lione is u.sed by siglit setters, by the fire-control party, and generally in all receiving locations where the type CP telephone is not em- ployed. 144 GUNNERY INSTRUCTIONS. RCCEUVCRS RtCClVCRS rVWu i** ,, TRANS. :i;el RUOGi & JACK TRAHS. =t= »^— PUUGi &. JACK PUUGi Spuuq Type CP telephone. Type CS telephone. «e:ce>ve:r5 tz XRAHS. i 1 U^ II I CON D. TV PC G-£ JACK W\TH TRANS ARCCEIVELR PLUGiS »NSC«TE.D. TO \.\NE. Type CT telephone. GUNNERY INSTRUCTIONS. 146 (d) Tyixi CT has the same characteristics as the type CS telephone, epccept that the transmitter and receiver plug sep- arately into a type G-2 jack, which is of special construction, containing a 2-m. f. condenser. On account of the cost of the special jacks few of these telephones are in use. Since two separate lines are necessary from the jack, the type is not considered entirely practical. 5= Operators ^ RE.cEivefi-4; 1 1 -TT T ^ ^ ^ _J) f ^ ^ Fig A. RE.ceive»t Pig. B. 330. Conditions governing' use of different types of trans- mitters. — (a) From figure A, note that on a given line all receiving sets, since they are plugged across the lines, are in parallel. Therefore, the current which goes through lines T and TT at the point indicated is the sum of all the current re- quired for each set of receivers, or the current of one set times the number of sets in use. The source of direct current for this line is B and BB and through impedance coils P and PP. Similarly, the source of 34776—18 10 146 GUNNERY INSTRUCTIONS. alternatiny or talking current for all the receivers is the transmitter M, which receives its impulses when sound waves strike the diaphragm D and cause it and the upper electrode (to which it is secured) to vibrate, thus varying rapidly the lesistauce in the small carbon particles and sending forth the impulses to the receivers. But if this transmitter were in series witli its receiver (instead of in parallel), its total out- RCCEltVERS KaMF COMDE.NSE.K PUOQ . Type CC telephone. put would be limited by the resistance of the receiving set; or the talking energy supplied for the whole line would really be only what is necessary for a small portion of it. Since a comparatively large amount of energy must be emitted from the receiver iu this case, it is obvious that the parallel connec- tion is the only practicable one. ib) For the same reason, on lines having a few receivers, a series connection is used (fig. B). It would be satisfactory to use a parallel connection on these lines, except that larger currents than necessary would flow through the transmitter, and in this case there would be danger of heating. It is considered more satisfactory always to keep the current (di- rect) as small as possible. In a CS telephone, as shown on sketch, it is obvious that the aiuount of current flowing through the transmitter is limited by the higher resistance of the receiver coils. GUNNERY INSTRUCTIONS. 147 331. New types. — All of the above-mentioned type.s are to be abandoned, and new types, as follows, furnished to all ships : (a) Type CC: The type CC telephone is modeled after the present type G telephone, except that the plug is so designed as to have a J-m. f. condenser Installed as a part of it, and the BELCEIIVCKS r-O l^ — o — I TRAHS w PUUCJ&JACK POSH Button Ijll Vz Mr CONOE.NStR B PLUG, Type CN telephone. receivers are in series. Tliis will enable all type C telephones to be lifted at small expense with condensers, and will neces- sitate no change in tlie present equipment other than the use of the new plug in place of the old, and a slight modification in wiring up the head set. (6) Type CN: The type CN telephone consists of receivers similar to receivers of the type CC telephone, in conjunction with a new design transmitter having conical electrodes, and also incorporating as an integral part of the set a ^-m. f. con- 148 GUNNERY INSTRUCTIONS. (leiiser. aud a cut-out push button, which uiust be closed wheu talking. New mechanical features of design have also been incorporated in this telephone. 332. Care and operation. — {(i) Test fire-control telephones daily. ( h ) Use spare telephones frequently, as a certain amount of usage, in addition to checking their condition, makes them more efficient. The worst thing that can be done for the effi- ciency of the fire-control system is to lay the telephones up where they will not be used for a considerable period of time. (c) Never carry a telephone by the cord, and grasp the top of the plug when unplugging. Telephones now in use have practically all the strain taken on the terminals, and these precautions must be taken to avoid pulling loose a connection, and thus rendering the telephone inoperative. (d) Avoid bending the cord sharply dver the edge of the terminal tube. This gradually breaks through the braid and insulation, in addition to straining the copper conductors, and a short circuit or open circuit results. ■ (c) When talking, keep transmitter in an approximately vertical position. If the transmitter is placed horizontally, transmission becomes very bad. since the upper electrode presses on the carbon particles ; and, consequently, the vi- brating impulses are dampened. In case the transmitter is in- advertently held horizontally, bring same back nearly ver- tical, aud tap sharply a couple of times with the hand ; normal operation should then be obtained. (/) Often, when transmitters have been used for a consid- erable period of time, heating is noticed. This is due. probably, to the large number of receivers to which the transmitter is connected, and the best thing to do is to put in a new trans- mitter, and allow the heated one to cool off gradually. (fl) Receiver diaphragms sometimes become hot: and, as a result, the paraffin melts, collects in a drop, and the receiver is practically deadened. It is a matter of only a few minutes GUNNERY INSTRUCTIONS. 149 to reiiiovo tlie cause ot the tnnil)U»; hut, ordinarily, it is better to use a spare liead set. and allow the heated receivers to cool off. The receiver diaphrauni can be put in condition again with little trouble. (h) C'l-oss tallc is caused most frecpiently by insufficient im- pedance ; however, if everything is going along normally and cross talk is noticed, the voltage of the system should be in- vestigated at once; llie chances are that 11 is high. Fre- quently, when imi)edance coils have been in use for a long time, it will be found necessary to reduce the working voltage several volts in oi'der to les.sen cross talk. 333. Impedance coils. — The impedance coil is an inductive resistance coil, whose fiuiction is to pi'omote the supply of di- rect cni-HMit to the telephone, and to conhue the variations of current caused by talking, which are alternating in char- acter, to its own circuil. Thus, in preventing the leakage of these altei-nating impulses to other circuits, the impedance coil performs its function of preventing cross talk. All tele- l)hones. in any circuit, are in parallel; therefore, the more telephones there are connected, the more current is needed in ;i circuit to give each telei)hone its proper share. For this i-eason, 3-ohm coils are used where a large number of tele- l)hones are employed, and 10-ohm coils where a small number are employed. Experiment has shown that 10-ohm impedance coils give good talking results with from 2 to 10 telephones, and that 3-ohm impedance coils give similar i-esults with from 6 to 20 telephones. 334. Condensers. — A condenser is an electrical appliance so constituted that electromotive force applied to it stores up energy in the form of electrostatic stress, which latter starts tills energy back in the form of current when the constraining electromotive force is removed. In the case of lire-control telephones, where the inductance (impedance) and capacity (condensers) are in series, the 160 GUNNERY INSTRUCTIONS. talking efficiency is improved. In sucli a case the only current which goes through the telephone receivers is alternating in character, and is generated when the diaphragm of the trans- mitter receives its impulses from talking, and hence is neces- sarily very small. Under normal conditions therefore, no heating or other deleterious effects due to the flow of current will be obtained in receivers when these small condensers are used. One-half m. f. conden.sers are used in series with the new fire-control receiving sets (tyjDes CC and CN). 335. Source of energy. — On vessels up to and including the Arkansas and Wyoming, the fire-control telephone switch panel may be energized by either of two telephone motor generators. Later ships are supplied with one motor gener- ator and a storage battery. The storage battery, like the motor generator, is arranged to supply the ship's service tele- phone system as well as the fire-control system. The battery is of sufficient capacity to supply current for telephones for a period of 30 days' continuous use. The storage battery, consisting of an appropriate number of Edison cells, is so designed as to " float in " on the line. The battery should first be charged from ship's circuit to its nor- mal potential, and then be thrown in across the motor gener- ator lines with the telephone outlets. The motor generator leads are fitted with a reverse-current circuit breaker. If, for any reason, the motor generator is suddenly stopped, or should the voltage of the motor generator fall below the normal re- quired, the battery, being across the line, will automatically take charge and supply the telephones, while the reverse-cur- rent circuit breaker will instantly open and thus prevent the battery being short circuited through the armature windings on the motor generator. 336. Specifications and telephone pamphlets. — IMore de- tailed information-of fire-control and ship's-service telephones may be obtained from specifications and plans which are on GUNNERY INSTRUCTIONS. 151 filo ill tlie liiii-t'iiu of Steam Kngineeriny;, (-((iVk's ol' whicli may be obtained upon request, and from Bureau of Steam En- gineering Pampldet No. 1773. The following books are rec- (>mmended : American Telephone I'ractice. by Miller. A P. C of the Telephon(>. by Homans. SW >TCM OM IMT. COM.SWBD. TE.UC.PHOISC MOTOR-G,CH. iriT. COt-l.ROOM . 2\JVI a 03 n GUNNERY INSTRUCTIONS. 166 166 GUNNERY INSTRUCTIONS. Tables have been calculated for " shorts," " overs," and " length of target in knots " for a range of 12,000 yards. For other ranges the calculations are made in a similar manner. [Height of spotter's eye, 120 feet from water line; range, 12,000 yards; 2,000 yards=l knot; a=l,000 yards; target, 30 feet high; effective spotting height=120— 27=93 feet.] " Shorts." hXa 93X1000 y~R^~ 11000 ~^'^ ^®* below water line or about one-third height of target. " Overs." hXb 93X1000 „ , ^ , , ,. ,. , , X ~p~irj>~ iQonn =7.1 reet below water line or slightly greater n-to 16WV ^j^^j^ one-fourth height of target. Length in knots of 60-foot target on 12-inch (2,900 f. s.) deflection drum— 12,000 yards, bearing abeam. 105X3 1 knot =—Y^ =26.3 feet and a target 60 feet long abeam is 2.3 ^^ knots. Long on 12-inch deflection drum. When bearing 30" it would be 2.3 X sine 30° — 1.1 knots. Hence, a splash appearing a target length to the left of target would require a spot of 2 knots right ; whereas when the target is abeam the spot would be 3.5 knots right. 361. Table of shorts and overs.-— Target, 30 feet high ; spot- ter's eye, 120 feet above water line ; range in yards. Column A— Distance of " slick" below ia feet. Relative proportion of target given approximately in Column B ; a=yards short of water line of target. 12-inch gun. 2.900 f. s. GUNNERY INSTRUCTIONS. 167 o <- . 42 ::;::: : ^ ! ! ; : : ! ; a a >? I ; ; I : I ; Q w >^ :::::: : 7 OS w N-^C^C^CO-rcOl^ 1 I 1 1 1 1 1 1 «< eo OS 00 N 00 to — 1 o r^-^t^cooir^^rf^ eo(M--<-^ «-H n 03 • •^CMco-^ior>»^-H 1 1 1 1 1 1 1 1 CO<— •'—<'—''— It— <•-'<— * -r CO (N C3 • CO -T 5D r^ ^ — — « 11 1 1 1 _!_ 1 I ci w m c o CO t^ ^ C t-' irf rr CO rq -H g ec 11 OJ M cc r^ t-H .^ CO CO CO 1 1 1 1 1 1 1 • OON—cot^ -r o irf V CO c*i T-* ^ § 7 03 n lOOCOOCO -HCOOT T»te as 1 J,J,J,^J^ 1 -^ oc o» o 05 -^ O t^ »0 T CO r-I 1-^ ^ ' ' ' ' 60 § toooo'c-rTr'co'oo f-t ^H ^H 1— 1 .-« Effective spotting beigtit. ■^ -tj -tj ! ; '. '. 9 a ®a)a o» 00 — ■"—"-" ■" «OOCOC^1COCOI> i-lf-t»-^Oi00C*»O'0 CO o COOOOO- CS.-HrH.-l CI ic eo -v CD (^ cs f-H »-H t-H CO W CO T *o h- Ci — 1 1 1 1 1 1 1 I— 1 00 »0 00 -^ TT -^ CO cir^*OTrcoc4 TT lo r^ 00 -^ -^ ^ 1 1 1 1 1 1 1 CO CO -^r t^ 00 «N ?o 00 o -n- CO cs c4 r-I O 00 rH rH ^ r-< CO 1 1 1 1 1 1 1 o CO 00 35 ^M h* -rr c:^ lO CO »-H C^ ^ 1-H 10*000000 rH ^ CO CO -.D ::? :s 1 1 1 1 1 1 1 t^OOiOO 00 CO O t^ iO -^ CO i-i 1-H i-H oooooooo sd'oo'cT cm" VcT 00 o" ^ ^ ^ -H -H jv) csoo-H*— '^ *^*-"*" ^ o o CO (N CO 00 r^ i-i^t-toioor^io-^ 168 GUNNERY INSTRUCTIONS. Analysis of tables.— On inspectiog the tables it will be seen that the values in column A vary directly as the distance of the splash is " short " or " over," so that at any range, if the .spotter remembers the value of " y " for 100 yards, he can tell what it is approximately for 500 yards. At ranges short of 10.000 yards the effect of the curvature of the earth is small, but should be considered. At 15,000 yards, neglecting the earth's curvature, a short of 1,000 yards, theoretically, would appear 8.5 below, whereas it will really appear 5.5 below. If a spotter estimates the slick to be 5.5 under, and considered his height as 120 feet, he would give a spot of " Up 600 " and then be 400 yards in error. This may sometimes account for '• under spotting " at high ranges. 362. Initial deflection. — To obtain tlie initial deflection, at- tention is invited to the problems given in chapter 17. The initial-detlectiou indicator, described below, is a ready means of obtaining the deflection due to speed of ship and target, not including the effect of wind. The construction of the initial-deflection indicator is as fol- lows : 1. Construct on cardboard a compass rose, indicating de- grees, and marking each 5° position. The inner diameter of this compass rose to be about 8 inches. 2. Construct the speed and bearing diagi-am as follows: Cut a piece of cardboard to circular shape, the diameter being equal to the inner diameter of the compass rose previ- ously constructed. Draw on this circular cardboard two di- ameters 90° apart. Mark one of these with an arrowhead for indicating the bearing. On the other diameter construct two sets of circles tangent to the bearing indicating diameter. The scale of these pircles should be such tliat a circle of diameter of at least twenty times the unit may be constructed on each side of the center. The diameters should vary by two units. GUNNERY INSTRUCTIONS. 169 3. Construct enemy arm from a strip of celluloid having a hole at one end for pivot, the remainder of the arm to be so cut that if extended the line would pass through the center of the pivot, as in the sketch. On this arm lay off and mark intervals from the center of the pivot on the same scale as that used for the speed circles. B MOVABUC ARM Cr CE.LLULOID PlVOTtD AT "A" C MOVABLE ARM or CE.LLULOID PIVOTE.0 AT "a" 170 GUNNERY INSTRUCTIONS. 4. Construct own ship arm similarly to enemy arm but lay off intervals from center of pivot on a scale one and one-half times as great as that used for enemy arm. 5. Secure all parts by pivot permitting motion of all parts except compass rose. To obtain the deflection, place the arrowhead on the inner card pointing to the true bearing of the target ; " Ovni ship arm " at the ti*ue course of the ship ; " Enemy arm " at the true course of the enemy (target). Th& intersection of the speed circle with " own ship arm " indicates the knots correction for movement of ship. Tlie intersection of the speed circle with " enemy arm " indi- cates the knots correction for enemy movement. These corrections are right or left depending upon whether the direction of motion is to the right or left of the bearing as shown in red and black ink. The total correction to be applied is the algebraic sum of the two corrections. 363. Deflection due to wind. — A convenient though not ab- solute rule for making allowance for the deflection caused by wind is to allow one-half of the force of the wind shown on the Beaufort scale. If, for instance, the wind is blowing with a force of 4 (Beaufort scale), 2 knots would be about the correct compensation. Data on the effect of a wind can also be obtained from the range tables, but this is believed to be no more accurate than would be obtained by the use of the fore- going rule. 364. Thumb rule. — A thumb rule for obtaining the initial deflection is as follows : (a) Correction ship's speed equals product of speed of ship in knots, times three-fourths time natural sine of angle be- tween course and bearing of target. This correction in knots applied to right, firing to starboard ; firing to port. GUNNERY INSTRUCTIONS. 171 (b) Correction target speed equals plotted speed of target in knots, times natural sine of angle between course and bear- ing of target. (c) Correction for wind equals one-li:ilf force in knots by Beaufort scale, times sine of angle between direction of the wind and bearing of target. (This is for the true wind.) A spotter in the top with a table of natural sines at hand for every 10° can quickly compute the initial deflection by using these thumb rules. If he has plenty of time, five min- utes for example, with his range table he can accurately calculate the correct deflection for each caliber of guns fired. 365. Tables of deflections (length of target on deflection 'drum in knots), assuming firing and target ships on parallel courses. 12-inch, 2,900 f. s. gun, full charge, target 60 feet long. Value of 1 Imot (feet.) • Length of target in knots bearing— Range. 90° 75° 60° 45° 30° 15° Yards. 6,000 11.8 16.3 21.0 26.3 31,8 37.8 44.3 51.0 5.1 3.7 2.9 2.3 1.9 1.6 1.4 1.2 4.8" 4.4 3.5 3.1 2.7 2.4 2. 2 2. 1.8 i 1.6 3.6 2.6 2.0 1.6 1.3 1.1 1.0 .8 2.6 1.9 1.4 1.1 .9 .8 .7 .6 1.3 8,000 .90 10,000 .7 12,000 .6 14,000 . 16,000 1.5 1.4 .4 18,000 1.3 1.1 1.1 1.0 •4 20,000 .3 Analysis of table. — An inspection of this table shows that the greater the range the smaller the length of the target in deflection; thus a 12-inch splash GO feet to the left of the target abeam 6.000 yards distant would be spotted " Right 8," while at 15,000 yards, " Right 3." It is important to remember this change. Attention is called to the effect of bearing of target upon deflection. (See art. 360.) 172 GUNNERY INSTRUCTIONS. 366. Parallax. — When tiring at short ranges, where the bearing of target changes rapidly, allowance must be made for position of spotter whether forward or abaft firing gun. For example, 12-inch gnu fires off starboard beam at a target l!,000 yards distant; speed of target, 5 knots; gun, 10 knots. During the time of flight the ship advances 21 feet. Hence, if a spotter stood abaft the gun 21 feet, he would be in the original line of fire when the shell splashes, and could most accurately spot on in deflection. 367. Diagram of lateral displacements. — In Figure IV is shown the lateral displacement of splash and triangles by which lateral coordinates of points in " splash diagram " of short range are calculated. Where range is over 8,000 yardfe an inspection of Figure IV shows that the value of X is so small as to be negligible, i. e., ratio of -j-^ small forsplashes within 100 yards of target. At 8,000 yards a .splash 1,000 short is displaced only about 2 feet for difference of speeds of target and firing ship of 10 knots when abeam. B E. -~-ir^ llo Fig. IV.—Lateral displacement of splash 368. Explanation of figure. — A ship moving 10 knots fires a 6-incli, 2,li00 f. s. gun when at A. The target T, 15 by 21 feet, is 2,000 yards off the starboard beam, and moving on a parnllpl course "> knots. The diagram shows gun making 5 GUNNERY INSTRUCTIONS. 178 knots and target anchored, which gives the same results. The .-•potter at A, 3.5 feet over gun, moves from A to B during time of fliglit of projectile from A to point of fall, S. His line of siglit to splash BCS, passes a lateral distance ./■ to the left of T. Assume this projectile iiit in corner of Al, 21 fee,t above the water : target 6 feet above water. From column 19, range rabies, using mean value of feet=100 yards. TS=3.50 yai'ds, approximately. Then from colunni 18 witli horizontal range^^ 2.350 yards (not distance of vun 1o the target) distance AB 20 5x3X5 (movement of spotter) is found to be — ~~Tn =25.6 feet. By similar triangles, CT or a?=3.8 feet. From a height of 35 feet the slick appears 5.2 above water line of raft. S' repre- sents splash short of target, and seen a distance y to right by spotter who has moved to E. Similar calculations are made for hits in corners of A4, Yl, and Y4. Having the vertical and lateral coordinate^ of these points a target may be pro- jected on the water. The coordinates ot the points necessary to project the ".splash diagram" are as follows (see columns 18 and 19, range tables) : Corner Al : x=3.8 feet to left of Al. y— 5.2 feet above water line raft. Corner A4: x=3.8 feet to left A4. y=5.2 feet above water line. Corner Yl : x=l.l feet to left of Yl. y=1.7 feet above water line. Corner Y4: x=l.l feet to left Y4. y=1.7 feet above water line. 174 GUNNERY INSTRUCTIONS. 369. Splash diagram for long rang'e. — Having calculated tables for use in long-range spotting by the "vertical" or "splash" method construct a diagram to scale. The slick lor range only is shown. (See art. 367.) These dia- grams should be constructed similar to Figure VI for (1000, 8,000, 10.000, 12,000, 15,000, and 18,000 yards for lioth high and low spotting positions. A study of them en- .-ibles a spotter to spot without reference to tables. The dia- gram constructed is for a range of 10,000 yards, target 30 by (50 feet. Raft 130 feet long, 4-foot freeboard forward and aft. Scale, 1 inch equals 15 feet. Spotting correction to water line. Horizon appears 15 feet above water line from tlie spotting position. 370. Training for battle. — As a preparation and training for battle, the spotter should study the types of ships of his ad- versai-y, considering all the dimensions obtainable. Such data as lengths, distance of foremast to stem, height of smoke pipe, height of tops, turrets, searchlights, and main deck, are valu- able. With these the spotter can construct battle diagrams to scale and use these known points and dimensions in spot- ting. In the first firing on the San Marcos a high explosive projectile was seen to detonate at the top of the smoke pipe, the kno^^'n height of the impact was used in giving a spotting correction, which permitted the firing of a salvo after but one ranging shot. GUNNERY INSTRUCTIONS. 176 m 176 GUNNERY INSTRUCTIONS. 9 ooo 6 a a a o in N m be I o o M a o 5<2 >. O o © © •♦J (N O GUNNERY INSTRUCTIONS. 177 371. Battle diagram. — A battle diagram (Fig. VII) has been made of a battleship of the Pennsylvania type for a meau rauge of 14,000 yards, 14-inch, 2,600 f. s. guns. The construc- tion and study of such diagrams would form a most important feature of the training for battle. 372. Salvo firing method of " shorts." — Single shots are far easier to spot than salvos. To spot the latter successfully requires much training and practice. When a salvo strikes, the spotter observes the splashes and estimates the point of mean impact, throwing out wild shots. He estimates by the " vertical method " how far this point is from the water line of the target; he then gives a spot such that the next bunch will straddle and fall at or near the water line. He must im- mediately decide: (a) The location of the mean point of impact or center of bunch with reference to the target. (&) Which, if any, were wild shots. (c) If the condition of the sea is affecting the slick. (See art. 404.) 373. Estimation of the amount of spot. — The sights are regulated by estimating the percentage of splashes short of the target, and by keeping the mean impact on the target. 374. Mean dispersion. — The amount of dispersion may be Judged approximately by estimating the total dispersion be- tween the limiting splashes in a salvo, throwing out wild shots, and dividing by three. 375. Chances of hitting. — For theoretically getting the proper percentage of shorts, attention is invited to the fol- lowing table, based on the chances of hitting (see Alger's Exterior Ballistics, Chaps. XIII and XIV), assuming that the mean dispersion in range remains constant at various ranges. Such a table is calculated for mean dispersions in range of 40, 60, and 80 yards, corresponding approximately to total dispersions of 150, 200, and 300 yards; mean impact at center 34776—18 12 178 GUNNERY INSTETXCTIONS. GUNNERY INSTRUCTIONS. 179 of djinger space and at water line; percentage of hits to be expected and percentage of short sliots to attain this percent- age of hits. 376. Spotting- table— Method of shorts.— /.^-i/fc/i 2,900 f. s. tjun, taryct 30 feet high lateral errors not cunsidered. 7,000 yards . . 10,000" yards . 13,000 ^•ards . 15,000 v;irds. 18,000 yards. Mean point of impact at | Mean point of impact at center of danger space. water line. Percentage. 1 ercentagc. 1 1 40 60 80 40 60 80 yards. yards. yards. yards. yards. yards. •i-a -..:» ki h ki b. u o -M o 4^ o *i O o '*^ o ■^^ ■ J3 H R m m J3 CO 50 50 Si 50 49 S3 50 46 4 93 12 77 19 63 14 72 24 53 30 40 50 49 50 42 50 35 25 49 32 36 37 27 SO 42 50 32 50 25 ' 29 42 36 29 40 21 50 36 50 27 50 21 : 35 31 40 21 42 16 50 28 50 20 50 ISJ Danger space (yards). 180 108 70 55 39 Note. — These mean dispersions are less than ha\e been experienced at recent practices. I'lie chances of liltting ai'o based only iii»<)u vertical errors; flue to lateral errors ihey are reduced cdnsiderahly on a short target. Assnining the mean pdlnt of impact on the target, it will be noted that as the mean dispersion is increa.sed, the percentage of hits decreases very i-apid1y. 377. Analysis of table. — From the table it is seen that: (a) A greater percentage of shorts is necessary at high than at low ranges. (b) Where a mean impact is some disiauce from target, an increase in dispersion gives more hits. Mathematically, the mean dispersion for maximum efficiency equals 80 per cent of distance from mean point of impact to center of danger space. 180 GUNNERY INSTRTJCTIONS. 378. The advantages of keeping- a number of shots short are: (a) Fire may be coutrolled more efficiently. (&) Splashes rising in the air will tend to demoralize enemy and obscure gun sights. (c) There may be ricochet and under-water hits. Shots that are over are lost. 379. Principles of spotting by shorts.— The following prin- ciples may be laid down for spotting by "shorts" : («) At long-range target practice keep approximately one- third of the shots short. (b) When a whole salvo is short or over target, give a spotting correction at least equal to twice tlie estimated mean dispersion plus distance from the target of splash nearest to the target. (c) If the salvo straddles with 90 per cent of shots short, give a spot "up" of twice mean dispersion; and with 75 per cent sliort, a spot equal to mean dispersion ; with 50 per cent short, malce no correction, if again 50 per cent are short give "up" 50 or 100. 380. Method of halving.— In combination with the method of "shorts," corrections are sometimes made on the principle of "halving." In getting on the target, after a first spot each correction is halved until the salvo is brought on. For ex- ample, first salvo all over 700 yards, spot, "Down 400," second salvo, over, one-half of first correction or "Down 200," third salvo on the water line. With the rate of change constant, the spotter is absolutely sure to get "on" in time with this method which, however, is slow. 381. Selection of spotters.— If practicable, the chief spottei- ought not to have a turret; other spotters should not have duties which will interfere with their training and work in battle. In making battery assignments consider what officers may be selected as spotters, and if they are given turrets de- tail junior officers who can take charge of the division in GUNNERY INSTRUCTIONS. 181 their absuiice. With tlie exception of the four senior olUcers in a battlesliip it is proper to assign any officer as spotter who lias demonstratetl liis excellence. 382. In selecting spotters the following are suggested: (<;) Only coninilssiuned ollicer.s .slunthl act a.s spotter.s. (b) Note records as spotters in previous practices, (c) Have eyes of candidates examined and require normal vision, (d) The natural (pialities to be desired in a spotter are even di.spo- sUiou. quick judgment, conlidence, coolness, keenness, and intelligence under adverse conditions; courage of his convic- tions at all times, (e) A spotter should have a knowledge of g\innery including ballistics', and the theory ;ind practice of fire control. METHODS OF TRAINING. 383. Officer in charge of training. — The training of spot- ters should be under the supervision of the gunnery officer, 384. Essentials in training.— (a) Require spotters to con- struct necessary diagrams, (b) Hold meetings for discussion of spotting, calculation of initial sight-bar rauge, errors of gun lire, and a general exchange of ideas, (c) Outline scheme of spotting drills and keep up drills throughout the year even for experienced spotters, (rf) Never criticise a spotter in action; any confusion will ruin a performance. After a drill or prac- tice, mistakes should be carefully pointed out. (e) Give spotters every opportunity to practice and observe the fire of other slnps. (/) It is desirable to train certain spotters for high and others for low spotting positions. 385. Training devices. — («) The fundaiiiental principle of any device for training spotters is that it should be realistic. Any device by which a small object is projected toward a tar- get simulating a projectile will permit an interesting and in- structive form of drill. (6) The spotting board or range should be as long as con- ditions will permit. 182 GUNNERY INSTRUCTIONS. (c) The target and height of the spotter's eye should be in rlie same reduced proportion as tlie actual range is to the spotting range. Never increase size of target to represent magnified image, as it destroys the true perspective. 386. Preliminary. — In the beginning set up a target to scale. Witii a wand point to the target, indicating hits and misses. Spotters note how much the projectile missed the target and give correction. These drills should be held until spotters can quicldy and accurately give a spot. Diagrams for different calibers and ranges posted in a spotter's room will aid in keeping in mind the proportion of target and spot- ting data. 387. Training for night practice. — The training for spotting for night practice at short range is carried along the same lines as for day. With diagrams previously prepared and studied a target is set up on deck at as long a range as possi- ble. The target is illuminated by a bull's-eye lantern. For simulating tracers, a wand is used, on the tip of which is placed a 3-candlepower light. This may be turned on or off to simulate a tracer passing over target. During the day the wardroom may be darkened and a similar range laid out 20 yards long with target built to scale, and drill conducted in the same manner. All persons who may be called upon to control torpedo-defense guns should be given this training, 388. Training for long-range spotting. — Division officers to train for spotting : Require all division officers to train for spotting in order that they may prepare themselves and petty officers for independent control. Never hold a drill without a number of officers present. Keep and publish records weekly. Encourage competition in spotting. 389. Training for long-range spotting is conducted as fol- lows by: (1) Drill at the spotting board. (2) Drill on spot- ting range aboard ship. (3) Subcaliber practice. (4) Obser- vation of practices. (5) Spotting practice. (6) Spotting at battle practice. GUNNERY INSTRUCTIONS. 183 390. Spotting board.— A spottins boaixl is a device by which long-rauge firing may be simulated upon a small scale, for the training of spotters. While the details of spotting boards vary, the following general principles of construction are com- mon to all: (a) The scale upon which a board is constructed is the ratio of the length of the board to the range, (b) The dimensions of target, splashes, height of spotters, and horizon on the spotting board bear this same ratio in comparison to the actual heights, etc. (c) The general perspective must remain the same as at the long range. 391. Dimensions. — Board to represent a range of 10,000 yards for 12-inch guns firing at a target 30 by GO feet. High spotting position, 120 feet. Low spotting position, 50 feet. Splashes, mean height, 173 feet; diameter, 20 feet. Eye to target, 30 feet. Scale of board, 1/1000. Target dimensions, 0.36 by 0.72 inch. Height of eye-high position, 1.2 inches; height of eye-low position, 0.3 inch, considering earth curva- ture. Mean dimensions of splashes, 2.1 by 0.48 inch. 50 yards on board equals 1.8 inches. 392. Drill at the spotting board. — Before the drill hour place spotting board where the light is good, little confusion, and no interruptions likely. Lay off a distance of 30 feet from target ; at this mark place a rest for a 3-power glass so that the eye of the spotter will be about 1.2 inch above the plane of the board. In a new ship start drill with the board as soon as officers are settled in their duties. Give all officers, , from gunnery officers down, drill at spotting. At first spot single shots, next salvos. In an hour 15 officers can spot two strings apiece, and at least this number should be given. Hold drill five times a week. 393. Procedure. — Before each drill arrange what splashes are to be used for the strings. Before each string, the spotter should study the appearance of shots short and over 1.000, 500, 200. and yard. From this practice will be learnesequent I'angiug shots. It is pidliahly 'hetlcr in all cases, using every available means and data at hand, to tire to hit the target on the first sliol. .Most spoitt'cs ])rcfci' lo have r;iiiging sliots sliort, as it i>-. in general, easier to estimate slan-ts liian overs; consequently, some ships purposely endeavor to tlirow the ranging shots short. This might be desirable were it possible to always coiiirol llic fire so as to throw the lirst shot IdU or liU(» yai-ds shoit. but so many errors are always present that tiiere is no absolute assurance as to exactly where the first shot will land, and a ranging shot landing some distance from the tnrgei will delay considerably the salvos. 410. Error in rate of change. — Witli a wi-ong rate of change it is almost impos.sible for the spotter to get or keep the shots on the target. The spotter should not, ordinarily, attempt lo coruMt f to the solution of problems of iiractical gunnery, in- volving- the use of range table data. 412. Problem 1. — Four shots wci-e bred on ( iililn-ation practice from a 12-inch gun, initial velocity 2,700 foot-seconds, weight (tf shell 870 pounds, inider the following conditions : Actual distance of target from tiring vessel 7,500 yards; height of- center of bull's-eye above water level 10 feet; sight of gun set for 7,500 yards; bearing of target from ship, north (Irui'l: wind from soutlnvest (true), velocity 15 jcnots per hour: barometer 30..50 inches; tliermometer (temperature jiir) 00° F. : temperature of powder 100° F. ; weight of shell 870 pouiKls (standard). Owing to lack of skill in the pointer each shot was bred with the cross wires of the telescopes 8 feet above the ci'nier of the bull's-eye. Measured from the foot of the perpendicular to the water through the center of the target the shot fell as follows: iNo. 1. .3.50 yards over, 15 yards right; No. 2, 150 yards over, 85 yartls right ; No. 3. 200 yards over. 20 yards right; No. 4, ;:'>00 yards over. 30 yards right. Find the mean error of the gun under standard conditions in range and deflection and the mean dispersion in range and ('cMection. 196 GUNNERY INSTRUCTIONS. No. of shot. Fall in range (yards). Fall in deflection (yards). Over. 350 150 200 300 Short. Right. Left. 1.. . 15 35 20 30 2 3 . . ^ 4)1,000 4)100 ^^e;^l i)()iut of impact 250 yards over, 25 yards right. Cor- rection tor 10 feet heiirht of center of l)uirs-eye. from range table column 7. 55 yards. JfO./ GUNNERY INSTRUCTIONS. 197 Observed mean error. In niiiLif. 11).") y;ir(ls <)\d for range of 7.500 yards. 1. Wind coniponent in line of fire. — Oonii">nent of wind in Hue of fire is 15 X cos. 45°. knots=10.6 knots. From the range table, column 13, a 12-knot wind in tlie plane of fire, if blowing with the shell, would increase the range 15 yards. Hence the present wind would increase the range 15/1 2 X cos. 45X15=13.3 yards. 2. Change of range due to variation of weight of shell.— In this ca.se. the shell being of standard weight, the change of range due to this element would be yards. 3. Change of range due to density of air. — From Table II. page 165, Alger's Exterior Ballistics, the density of tlie air for temperature 60° V. and barometer 30..50 inches is 1.031 or 3.1 per cent greater than standard. Tlie ]-ange tables are based upon temperature 59° F. and 29.53 barometer. From the range tables, column 12, an increase of 10 per cent in density woidd shorten the range 122 yards. Therefore, 198 GUNNERY INSTRUCTIONS. the decrease in range due to 3.1 per cent increase in density of air=122/10X 3.1=37.8 yards. 4. Chang-e of range due to temperature of powder. — From tlic ransie tables, column 10, tlie standard tem]teratiire of tin- powder is 90° F.. and an increase of 10° in the temperature would increase the muzzle velocity by 3.") foot-seconds. It is also noted in range tables that a change in uuizzle velocity (if 50 foot-seconds would change the range 215 yards. Hence. increase in nuizzle velocity is 35/lOX (100-90) =35 foot-sec- onds, and increase of range due to this inci-ease of nnizzl<> velocity will be 215/50X35=150.5 yards. 5. Correction for point of aim. — From the tables again, colunm 19. the increase of range due to raising the point of impact 18 feet is 100 yards. Therefore the increase due to aiming 3 feet high is 100/18X3=16.7 yards. 0. Summary of correction for range.— Compared to the range of a standard shell, the shots tired under the conditions of the problem would fall, for each variation in conditions, as follows: Yards. Over. Wind. 13.3 Weight of shell Ocnsityofair. , Temperature of powder ^^"- ^ Krror in aim ^"" ' Sum . 180. .5 Short. 37.8 37.8 Yards over. Correclion to moan observed error in range= Mean observed error in range ^difference 142. 7 195.0 True mean error in range (imder standard conditions) • ••>2- 3 GUNNERY INSTRUCTIONS. 199 7. To correct the observed mean error in deflection. — liy siiiiihii- process from riiiiiiv taltlc. coliiiiiii H',, the wiinl coni- lioiit'iii would produce ;i detlection of 7/12 X1.">X sin. 4r»°=(».'J yjirds riulil : wJucli apiilied to tlie " o))serveil nieiin error in detlection " of •_'."! yards, would uhe the " true mean error in dellei-tioH ■■ under sraiidard coudilions lo l>c iM — 0.2=18.8 >ards riirlit. 8. Final results for this one gun. — 'I'lie linal results for this ;;iui show that if it were aimed at the hulTs-eye of the tarjret. as l>efore explained, its shot would, under standard conditions, fall 52.3 yards beyond (over) and IS.S yards to the ritrbt <»f where they should fall, 1. e.. under standard con- ditions its mean error in range is 52. B yards over and its mean lateral eiror or mejin error in deflection is IS.S yards ii,i:ht. From colinmi 18 of range tables, for lateral motion of target perpendicular to line of tire for speed of 12 knots, the deviation is found to be W yards. K'olunui IS is used because all detlection di-ums are graduated in knots, consider- ing gun stationary and target moving perpendicular to the line of fire.) Hence, for a lateral deviation of 18.8 yards right at 7.500 yards range the deflection dr\im .scale should be cor- rected ]8.8Xi^ knots=3.8 knots. If the distauce of each shot from the mean point of im- jiact be measured and the mean of these distances l)e found, we have a quantity called the "mean disi)ersion from the mean point of impa<-t.'" This information is desirable because it gives an idea of the acciu'acy or consistent shooting of a gun. For example, one gun of a ))attery may have its mean point of imi»act, with reference to a certain target, 100 yards over and 25 yards right, but all the shots may fall within a very few yards of this point and be closely grou])ed around it. Another gun of the same battery may have its mean point at the same point, i. e., 100 over+25 right, but its shot may he so scattered or dispersed with reference to the mean jtoint 200 GUNNERY INSTRUCTIONS. of iiujincl llial I he .-ivcra^ie of tiieii' di.stances Jroiu the mean IMiiiit \ D=/( cot coV "'"" X ) and D where ]>-^danger si)ace and /i = lieight of target. Tlie first fornuUa gives 1> accurately enough for present liurp()ses. and we will use it. ()' iwfiea. D= 30 cot 11° 08' log 30 =1.47712 log cot 11° 08'= .70598 D=152.44 feet. log D =2.18310 =50.81 yards. 8 inches. D=30cot8°04' log 30 =1.47712 log cot 8° 04'= .84855 D=212.67 feet. log D =2. 32567 =70.89 yards. 202 GUNNERY INSTRUCTIONb. 12 inches. D ^30 cot 5° 41' log 80 =1.47712 log cot 5° 41' =1.00209 D=301.445 feet. log D =2. 47921 =100.48 .yards. Agaiu referring to Alger's Extericir Ballistics, Chapter XIII. on Accuracy and Probability of gunfire, and to the table on page 129 in which, in the case we are considering, a equals one-half the danger sjtace of rhe target, and y eciuals the mean erroi- in range: Case I, 6-inch gun. T ^1 • 50.81 yards „^ „,- j In this case, n = -^ =25.25 yards. and 7=mean error in range, or 50 yards. «=2^5=.509 7 50 Entering the table on page 129, referred to above, we find the value of P corresponding to this value of— to lie betveen 3.10 and .368. By Interpolation : ■^^^-■^^\^09=.00522 .1 or the corresponding value of P for .509 'is .315. That is, we may expect, under the given conditions. 31.5 per cent of 6-inch hits. GUNNERY INSTRUCTIONS. 203 Case II, 8-inch gun. 70.9 , _ ,. , «= ^— yards = .io.4o yanlt^ 7=39.5 yards. a 35.45 ,,^_ = on tc =^9< 7 39.5 P=.52G Tluit is we iu;iy expect. uikUm- the uiveu conditions, 52.6 per (•(Mit of 8-inch hits. Case III. 12-iiich (/tin. 100.48 .. _ , (!=' —^ — =50.24 yards 7=40 yards a 50.24 , ^.,. 7 40 P=.683 That is, we may expect, inider the liiven rojulilions. 68.3 per cent of 12-incli hits. 414. Problem 3. — To find angle of departure for an ele- vated target. — .Vn aeroplane is lioverin,s; over a point 2.000 .\ai-ds distant, in a liorizontal line, from a 3-iuch gun firing a 15-i)ound shell with an initial velocity of 2,500 f. s. If tlie altilnde of the aeroplane he 1.000 feet, wliat sliouhl he the angle of departure to hit it? .\11 conditions are standard f=l. B = l. Snhtiion. — In this problem tlie angle of position is such that ilic priiHJple of •■ rigidity of trajectory " liol.44: 5=1.05. .\t the instant you are (>.(><»<• yar0 F. ^ , , cent anove normal. 206 GUNNERY INSTRUCTIONS. Tciniicratui-t* of i)()W(lei"=7")° V. Xoniial teiiiperature of IKPwdcr is 90° F. Therefiu'c. iliis jMiwiler is 90 — 75=15° be- low normal. / "^ ><■ Resolving force.s ± and 1 1 to plane of fire we have: .'^peed of ship li to plane of fire=15 cos 45 =10.61 knots. Speed of ship ± to plane of fire=15 sin 45 =10.61 knots. Speed of target 1 1 to plane of fire=15 cos 22^=13.86 knots. Speed of target ± to plane of fire=15 sin 22^= 5.74 knots. Speed of wind ± to plane of fire= 12.00 knots. From 12-inch Range Tables, range H.OOO yards: (a) Column 14. Change of range for motion of gun in plane of fire, speed 12 knots=37 yards. .-. Change for 10.61 knot8=^^^^^ig^^=32.71. (b) Column 17. Deviation for lateral motion of gun ± to plane of fire, speed 12 knots=42 yards. .'. Deviation for 10.61 knot8= — '-j^ — ^=37.14. (c) Column 15. Change of I'ange for motion of target in i>lane of fire, speed 12 knots=47 yards. iQ »fiv47 .-. Change for 13.86 knots=^^^^^ =54.29 yards. GUNNERY INSTRUCTIONS. 207 (d) Column IS deviation for hiterul motion of target J. to plane of fire, speed 12 knot8=47 yards. 5 74X47 .•. Deviation for 5.74 knot8= " ,.-, — =22.48 yards. {(') Column ill. Deviation for lateral wind component of 12 knots =5 yards. (/) Column 12. Ohaiige of range for variation of density of air of ± 10 per cent =83 yards. .•. (hauge tor o per cent = - i^- =41.0 yards. (g) From "'Explanatory notes" in front of Range Tables a change in temperature of powder of 10° F. causes a variation in muzzle velocity of 35 f. s. .•. Variation of muzzle velocity for 15° F.=52.5 f. s. Column 10. Change of range for variation of muzzle velocity of ±50 f. s.=175 yards. .". Change for 52.5 f. s. = — '-^ =183.75. oO These I'esults are tabulated as follows: 12-inch, 6,000 yards. Argu- ment. Over. 32.7 Short. Right. Left. t'luiiigi' of rangi' for iiiolion of fun in plane of fire 10. til 10.61 13.86 .^.74 12 -t- 5 -15 Deviation for lateral motion of gnnltoplane of fire .... 37.1 Change of range for motion of target in plane of fire 54.3 Deviation for lateral motion of target X to plane of fire . . 22.5 De vial ion for lateral wind component Change of range for variation in density of iiir per cent. . Change of range for variation in tempera- ture of powder degrees. . 5.0 41.5 183.8 ^— -uit ^i^rS'-: 1 32.7 279.6 32.7 59.6 5.0 5.0 1 246.9 54.6 208 GUNNERY INSTRUCTIONS. .-. Sight bar should be set 6,000+246.9=6,246.9 yards. .VcTuiillv the setting would V)e 6,250 yards. The (U'tiectiou scales being graduated for "knots speed of target." .")4.6 yards must be converted to knots speed of target. Column 18. Deviation for motion of target J- to line of fire, speed 12 knots=*47 yards. liorfh • ^V^ y^ineJ l2Hhoh eooo ^ds 12 .-.1 yard=T^ knots. ^4 fivT' .-. 54.6 yards= '^^ " =13.94 knots. The graduation 50, being zero deflection, to compensate for 54.() yards, the drum must he set at 50—13.94=36.06. GUNNERY INSTRUCTIONS. 209 A<'tu!illy, the settiii.u' wmild he 'M'>. 416. Problem 5. — To find range and deflection for open- ing fire under service conditions. — Plot this situation before Wfirkiii^' tlR' problem. Vdu are chief fire-control olhcer of a hattle.ship carryln.y 12- iiich and (i-iiich .^uiis, and have been ordered by the cai)taiii 1(1 (>iien tire with the 12-inch the instant the range is ',).<)0() yards, heai-iiii;' north. 'I'he speeds and courses of the enemy and yourself at the in.stant of firiiiii are as follows: Eiiciiuj, course 4.j°. speed 12 knots: ///■///// xliii). course 300°. speed 1.5 knots, and this in- formation is known to you sutticientlx in advance to allow fo; variation from standai-d conditions in setting your sights. If the bai-ometer is 29 inches, thermometer 75° F.. temperature of the powder 95°. and the wind, from the west, is blowing 12 knots over the surface of the water, what would be the ~ range at which you would set the 12-inch sight bars for the opening sholV If the deflection scales of your guns are graduated for the speed of the target in knots, and the middle line of zero de- tlections is marked 50, bow would you set the 6-inch and 12- incb detlectioii scales for opening bre in the i)roblem above? Sohttioii. [From Table II, Alger's Exterior Ballistics.] Taking 1.00 as normal density of Barometer 29.00 Thermometer 75° F 5 = .9o' atmosphere, 1.00— .95=5 percent be- low normal . Temperaiure of powder 95° F. Normal temperature of powder is 90° F. Therefore this powder is 95°-90°=5° above normal. Resolving forces 1 1 and J. to plane of fire we have: Speed of ship 1 1 to plane of fire=15 cos 60=7.5 knots. Speed of ship ± to plane of fire=15 sin 60=12.99 knots. Speed of target 1 1 to plane of fire=12 cos 45=8.49 knots. .34776—18 14 210 GUNNERY INSTRUCTIONS. Speed of target 1. to plane of fire=12 sin 45=8.49 knots. From 12-in('h range tables for range of 9,000 yards; (a) Column 14. Change of range for motion of gun in plane of fire for speed of 12 knots=52 yards: .". Change for 7.o knots=— yp — =32.5 yards. {b) Column 17. Deviation for lateral motion of gun I to line of fire speed 12 knots=63 yards. 19 9QV63 .-. Deviation for 12.99 knots=^^^y^ =68.198 yards. (c) Column 15. Change of range for motion of target in plane of fire speed 12 knots=74 yards. • .•. Change for 8.49 knots= ' ' ^ — =52.355 yards. (d) Column 18. Deviation for lateral motion of target ± to line of fire speed 12 knots=74. .■. Deviation for 8.49 knots= ' " ,,-, — =52.355 yards. (r) Column 16. Deviation for lateral wind component of 12 knots 1 to plane of fire = ll yards. (/) Column 12. Change of range for ± 10 per cent variation in density of air=174 yards. .'. Change for 5 per cent variation = ^ =87 yards. (g) From explanatory notes in front of range tables a change in temperature of powder of 10° F. causes a change in muzzle velocity of 35 f. s. .■. Change for 5° = — ,-^^-^ = 17.5 f. s. Column 10. Change of range for ± 50 f. s. change in muzzle velocity=2.54 yards. 17 5V254 .-. Change for 17.5 f. s. = — ^^^^ =88.9 yards. These results are tabulated as follows: GUNNERY INSTRUCTIONS. 211 Argu- ment. Over. Short. Right. I^fl. Clmntio ol range for motion of gim in plane of lire ... 7.5 12.99 8.49 8.49 12.0 + 5 + 5 32.5 Dcvialidii for lateral motion of gim 1 to plane of /ire 68. 2 Change ol niiige for motion of target in plane of fire 52.4 Deviatidii for lateral motion of target 1 to plane of five. . . 52.4 1 )eviat ioti for lateral wind component 11. Change of range for variation of density of air per cent . . 87.0 88. 9 Change of range for variation in temperature of powder degrees. . I--, 1 .. n /I5(i yards over.. . 208.4 52.4 52.4 11.0 120. 6 '•'"'^''^■^"'^ {l09.6 yards left.. 11. J 156.0 109. 6 .-. Sight bar should be set at 9,000-156=8,844. Actually it would be set at S.S.IO yartls. The detlectioii scales of all yuus are ^iraduated for "knots s[)eed of target," therefore the l()9.G yards must be converted to knots speed of tarjjet. Column 18. Deviation for motion of target ± to plane of fire speed 12 knots=74 yards. .■. i yard=12/74 knots on drum. ion« A 109.6X12 ,_^, ^ , . . 109.6 yard8= ^7 — =1/.// knots on drum. 'I'lie uraduation .">() being zero deflection to compensate for 10!). G yards left we should set drinn at .")0+]7.77=(!7.77. Ac- tually it would be set at 68.0. For the 6-inch guns the method is tlie same, using the (i-inch range tables for O.OOO yards. From colunuis 1(5, 17, and 18 we find that due to wind. speed of ship, and speed of target X to plane of fire the shell would 1h' displaced 118.03 yards to the left of target. (In this case we are not concerned with the error in range.) 212 GUNNERY INSTRUCTIONS. ! Argu- ment. Deviation for lateral motion of gun J. to plane of flre Deviation for lateral motion of target J. t o plane of fire . Deviation for laleral wind component 12.99 8.49 12.00 Right. Left. 31.0 31.0 76.86 72.17 149. 03 31.00 118.03 From ('oiiuiiii IS tlu' deviation for 12 knots speed of tar- get=102 .vard.><. 118x12 For 118 yards it would be 102 =13.88. .•. Deflection scale should be set at 50+13. 88=();i. 88. Actually it would be set at 64. 417. Problem 6. — (1) To find change in sight-bar range when shot does not hit bull's-eye; (2) to find fall of shot when sights are not corrected for wind and speed. — Using tile 12-in(li range table, determine tlie following: (1) .\ iiun is fired at a vertical tarj^et screen 2,0(M» yards ('isiant with si,iihts set for a range of 2,000 yards. The shell I'iei-ced the target 6 feet ahove the buirs-eye. Wliat siglit-bar range nmsi l)e used if the next sliot is to hit tlie bull's-eye? (2) At a certain instant a ship, steaming at lo knots on a northeast course, is directly south of a stationary target which is 8,000 yards away. An 18-knot breeze is blowing from west-southwest at the time. Find the changes in range and (Ic/lcctioii due to (1) speed of ship and (2) wind; and state wliere the shot would fiill if the ship fires, at the instant noted above, with the sights set for 8,000 yards and no deflection. Solution. — ( 1 ) F"'roni 1 2-inch range tables, range 2.000 yards : Colunui 19. Chaufici in height of imiiact for variation of ±100 yards In sight bar=4 feet. GUNNERY INSTRUCTIONS. 213 Change for 6 feet height of impact=150 yards. Set sight bar at 2000-150 = 1.850 yards. ,1<'^' :Jrip (2) Ke.sdlviiijj; forces -L iiiid II to plane of fire. Speed of siiip II to plane of tire =15 cos 45=10.61 Ivuots. Speed of ship -L to plane of fire =15 sin 45=10.01 Imots. Speed of wind II to jdane of fire =18 cos 67A=()..S!t knots. Speed of wind -L to plane of fire =18 sin 67^=16.03 knots. From 12-incli range tables, range 8,000 yards: (a) Oohunn 14. Change of range for motion of gun in 1)1 ane of fire, speed 12 knot.s=47 yards. . , . 10.61X47 ., .„ , .-. Change for 1(1. (Jl knots= j^^^— =41.56 yards. {b) Colnnm 17. Deviation for lateral motion of gun -L to plane of fire, speed 12 knots=56 yards. .-. Devi:)ti(.n for 10.61 = - ■y;^"=49. 51 yards. {c) Coiniiin i:;. (Mianiiv of range for wind comi)onont in plane of fire, speed 12 knots=17 yards. 6.89X17 „... .-. Change for 6.89 knot?= — ^ — =9./() yards. 214 GUNNERY INSTRUCTIONS. (d) Coluum 16. Deviation for lateral wind comitonent of 12 knots=8 yards. .". Deviation for 16.63 knot8= — -rr^ — =11.09 yards. These results are tabulated as follows : ' Argu- ment. Over. Right. Change of range for motion of gun in plane of Are Deviation for lateral motion of gun x to plane of fire Change of range for wind component in plane of fire Deviation for lateral wind component 10.61 10.61 6.89 16.63 41. 56 '9.'76' ' 49.' .51 ii.69 51.32 60.60 ( '=30U', is e(iual ti) half the danger space. 419. Problem 8. — To find change in range due to varia- tion from standard (1) temperature of powder, (2) initial velocity, (3) weight, (4) density of air. — Using the 12-ineh range tal)k'. determine the following: (1) What would be the change of initial or nuizzle velocity if the tenii)eratur(> of the charge were 101° F. in.stead of 90° v.. for wliicli the range t:ibles were caleulated V (2) What will be the chanue of range due to this change in nniz/.le velocity if the angle of dopartm-e be 3° 12' V (3) If the gun is fired at this elevation (3° 12'). standard eondition. except that the shell weighed S2() pounds instead 216 GUNNERY INSTRUCTIONS. of 870 i)()im(ls. liow imicli will the ranjie be increased or de- creased ? (4) All conditions being standard except the density of the air, which is 5 per cent greater than normal, what will be the range of the shell if it is fired with an angle of departure of 3° 41'.9? t^oliition. — (1) The teniperatnre of the charge is 101° — l)(l° = ll° above normal. From explanatory notes in front of range tables we find that a change of 10° F. in temperatnre of powder changes the initial velocity 35 f. s. .'. 11° above normal increases the initial velocity by 38.5 f. s. (2) From columns 1 and 2 an angle of departure of 3° J 2' gives a range of 8.000 yards with normal initial velocity. To find change due to initial velocity, increased as in (1) — that is, by 38..J f. s. — proceed as follows: Column 10. Change of range for variation of ±50 f. s. initial velocity=229 yards. .-. Change for 38.5 f. s. =^^^^^=176.33 yards. (3) Notp:. — Charge remaining the same, weight of .shell in- creased, will it go farther or less with the same angle of (ieparture? The following net result was determined from pi-oving-ground data : For each case the initial velocity is reduced with heavier sliell and the range for short ranges is decreased and foi long ranges is increased. Column 11. Variation for ±10 pounds in weight of projectile= 39 yards. .•. Variations for (870— 820) 50 pounds=195 yards increase in range. (4) From colnnms J and 2 an angle of departure of 3° IT.O gives a r;inge of 9,000 yards under standard conditions. Column 12. Change of range for variation of density of air of ±10 per cent=174 yards. GUNNERY INSTRUCTIONS. 217 5X174 .-. Change for 5 per cent=--^Q— =87 yards decrease. Tlierefc.re actual raiij;e=9.000— 87=8,913 yards. 420. Problem 9. — To find range and deflection for open- ing fire under service conditions. — ]>ra\v a diagram of the si1uati. Dovintion lor l:it(>r:il wiiitl i-Dinpoiieiit, siteoil 12 kn()ts=8 yards. .-. Deviation for 14.49 knot8=-^^j2 — ""^-^^ y-Auis. {(/) Coliiiim 12. (Miiiujie of range for variation of density of air of + or — Kl iter (•ent=136 yards. 2 2X136 .-. Change for 2.2 per cent= -^^ — = ( /( ) From explanatory notes in front of range tables a change in temperature of powder of l(t° F. causes a change in mu;'-zle velocity of 35 f. s. .-. Change for 7° = '-^=24.5 f. .s. Cohnmi 10. Change 5 = 3.33 knots. a^herefore the deflection drum sliould be set at 50+3.33=53.33. Actually it would l)e set at 53. (2) For the 6-inch deflection the method is the same, using the 6-inch range tables for 8,000 yards. From columns 16, 17, and 18 we find that due to wind, speed of ship, and speed of target 1 to plane of fire the shell would be displaced 12.75 yards to left of the target. (In this case we are not concerned with the error in range. ) Argu- ment. Right. Left. Deviation for lateral motion of gun 1 to plane of fire Deviation for lateral motion of target 1 to plane of fire. . . Deviation for lateral wind component 4.66 9.13 14.49 24.46 "28.' 98' "66.' ig 53.44 66.19 53.44 12.75 Column 18. Deviation for lateral motion of target 1 to plane of fire, speed 12 knots=87 yards. ..1 yard = ny knots. .". 12.75 yards = ^~ — =1.76 knots. 0/ Therefore the deflection drum should be set at .50-(-1.76= 51.76. Actually it would be set at 52. CHAPTEK 18. STATION BILLS. 421. Scope of chapter. — The followiiii: is a hriol' outiiiir of ii. lire-coutrol bill for an all-big-guii ship. Numerous varia- tions of the plan herein outlined will !)e found, and it is not at all correct in detail for all shij)s. The method of using tlie system of communications varies. Some vessels use clocks in subcentral. vi^hile others rely on curves for tracking the enemy, or for graphically keeping the range and change of range. The general plan of tire control in all. however, is the same. 422. Station bill and lookouts. — In drawing up the sta- tion bills particularly for torpedo defense, proper regard for conditions of sei'vice should be observed. Othcers and men must be given stations that they could occupy and an ar- rangement of reliefs nuist be provided as would be the case in war when an engagement might be inuninent. ( il ) l'il( -roiilrol- — Firc-cdiilrol ioifcr jh'oiii). Person- nel. l>uty. Designation. Collective fli-e. Group fire. (^hief fire control, J . A . phone. Fire - control lower spotter, J. C. phone. J D. control Officer. . ...do Man ...do Oflicer. . Chief ftrc-control offi- cer talks to flrc-con- trol switchboard. Kelief spotter ring salvo signals. Talker to turrets Talker to range Imdcrs and timekeepers. Fires torpedoes Chief fire-control olliocr spot one group if nec- essary. Spot cither group as needed and ring salvo signals. 1)0. J. W^. control Torpedo director Do. Do. 221 222 GUNNERY INSTRUCTIONS. (b) iSuhcoitral yrouij. Designation. Subcentral . . Rate plotter. Clock Dials. Check clock . Check dials. . Tracker Tracker assistant Timekeeper Tube man Switchboard Fire-control repairs. Duty. Person- nel. Collective Are. Group fire. Officer. . Charge of subcentral, ' on J. A. phone. ...do Plot range-finder ob- servation on rate of change board. Man Operate main clock. . . ...do I Operate main dials — .do. .do. Officer. ..do.... Man .do. .do. Electri- cian. Operate check clock. . . Operate check dials. . . Tracking board Assist at tracking board. Mark time for range finders: repeat and record ranges and bearings; phone to range finders. Repeat voice -tube communications. O perate fire-control phone switchboard. Oyro compass and re- pairs. Charge of subcentral. Same as collective fire. Operate clock for after group. Operate dials for after group. Operate clock for for- ward group. Operate dials for for- ward group. Track for after group. Track for forward group. Same as collective fire. Do. Do. Do. GUNNERY INSTRUCTIONS. (c) tiaOyrouiJ. 223 1 )osiKnat ion Dulv. In charge | In charge. Telephone range and deflection to turrets; operate deflection 1r;insmitter. Operate range tran.s- raitter; stand by voice tubes. 'telephone range and deflection to after group; operate range and deflection trans- mitter to after group. Operate range and de- flection transmitter to forward group; telephone range and deflection to forward group. ( (I ) l'(ir(-t(>ii (iniKp. Dosigiialion. Fore-lop spotter. Fore-lop talker.. Bearings Person- nel. Duty. Collective fire. Group fire. Officer . . Spot all tuiret s Spot forward group. Man. . .. Tube to subcentral I Same as collective fire. . . .do. . . .! Bearing indicator ' Indicates l)earing for ' forward group. (e) Main-toi) group. Designation. Duty. Person- nel. ] Collective fire. Group fire. Main-top spotter Main-top talker 1 Officer . . First-relief spotter Man Tube to subcentral — 1 Spot after group. Same as collective fire. 224 GUNNERY INSTRUCTIONS. (/) Torpiilo-ciml rol f/roiiji. Designation. I tut v. Torpedo (.flicer Torpedo romn. Torpedo director officer At toritedo director. (//) Hiniav-liixlcr (/roup. Each crew c(»iisists of an otHcer and man (or two men). Foi- collective tin any one or all may he designated to i-ange. For f,a'oup fire the system is Mexiblc. and any twd may he designated, each for one .lirou]). ronmuuiicate hy iihone or \(iice tube to the tire-control tower and suhccntral. (//) Turret (jroui). In case the fore-top spotter, the main-toi» spotter, and the fire-conti-ol-tower spottei- are disabled, but ship is still able to tiglit all guns : For collective tire the turret officer of the liighest tunvt spots from his turret. For groui» fire the turret otHcer of the highest turret iu each groui> spots for tluit group. 423. Operation of system. — On apiiroaching the target the taking of ranges and bearings is conunenced on order from the tire-control station. At tlie order "mark" stop watches are started by men at each range finder, at the station where the bearing of the target is obtained, on the line of communi- cation in the subcentral. and in the tire control station. The numbei- of timekeepers is less than thos(» enumerated above in .some <'a.ses. With proper means of connnunication to sta- tions numerous variations in details are found. Loss of one means of communication does not entail the loss of the services of any station, but necessitates the shifting to the best auxiliary method of connnunication. At evei'v half aUNNEEY INSTRUCTIONS. 226 minute, if pussible, a rauge-liuder reudiug is obtained. One range liuder, tlie best, is used, tlie otliers standing by. or the mean of readings of all instruments is taken. Bearings of the target are taken every half minute, if a bearing indicator, wliic-li constantly indicates the bearing of the target, is not installed. These bearings are relative to the ship, and in degrees from 0° ahead around to 360°. Information regarding the range and bearing of the target is sent to the plotting board, and plotting to obtain rate of change of range and course and speed of the enemy is begun. The range clocks are located near the range dials, so that the dial operators may watch the clocks. The clocks are rated for the proper rate of change of range as soon as a rate is determined. If all guns are l)oiiig used on the same target, all dials are set simultaneously with the master clock when the clock operator calls out the range and only one range clock is used, the other being a stand-by. The man at the deflection board, taking the approximate rate at which the enemy is approaching, referred to a course parallel to the ship's course, and using bearing of the enemy as the other factor, automatically obtains the necessary deflec- tion. The ranges are sent to subs by the range dials and from the subs are sent out by visuals, telephone and voice tubes giving the information several seconds later. The chief fire-control officer designates the turret to ftre ranging shots, and at the order to begin ranging "fire" is dis- played on all visuals. The turret designated to fire ranging shots is notified from the sulis. if a previous notification has not been given. • When a ranging shot is fii'ed the spotter sends down the spot by visual iiulicator, telepluine. and voice tube and directs "fire second ranging shot" or "open salvo," as necessary. The chief fire-control officer is informeil of the spotter's first correction, the spot is given to the plotters, who 3477fi-^-1S 15 226 GUNNERY INSTRUCTIONS. make their corrections and pass the result to the range-clock man. As soon as any change in range or deflecion is sent out by the visuals to the turrets, "set" is called out from the sub- central over the J. B. phone. If no change is to be made, the word "set" or "no change" is called out immediately. As soon as the chief tire-control officer gets the word "open salvo," as described above, he orders the salvo signals begun. The person controlling the salvo signals wears a phone and waits for the word "set" from the subcentral, then sounds the bells and buzzers in accordance with the prearranged plan. If it is found that the rate of change obtained does not keep the salvos straddle of the target, the plotted line is changed one-half the change indicated by the spots. No changes in range are sent out to the turret after a "stand-by" signal unless a change of more than ]00 yards is required, m which case the subcentral directs "hold the fire," and the salvo- control officer holds the fire until he hears "set." Each turret employs a definite system in locally controlling the fire. Some latitude is given to the turret officers, and minor features vary somewhat in turrets, although the gen- eral scheme is the same for all. In each turret are three salvo bells and three buzzers, one bell and one buzzer near each elevating pointer and one bell and buzzer in the turret officer's booth. Thus, each elevating pointer and the turret officer are notified simultaneously regarding salvos. In the turret officer's booth are sets of switclies, one for signal lights and one for firing circuits. In case single-barreled salvos are used, the turret officer throws a double-throw switch, which flashes a light close to the eye of the pointer of the gun designed to fire and another overhead in the rear of the opposite gun, thus notifying the opposite gun that the other 1:? to fire. In case double-barreled salvos are used, the turret officer flashes the light close to the eye of the firing pointer GUNNERY INSTRUCTIONS. 227 ai>d throws the necessary firing-circuit switch to fire double barreled. In case it is desired to cut out a turret or turrets, the necessary switclies are thrown by salvo operator in fire- control station, and consequently bells and buzzers are not rung in the turret or turrets cut out. 424. Cease firing. — At " cease firing " the chief fire-control officer directs "cease firing" over the telephone. The word is passed over voice tubes and phones to turrets, and "cease" is displayed on visuals. Tlie salvo signals are stopped, and the "cease fii-ing" gongs are rung from the fire-control station. 425. Torpedo firing. — The course and speed of the enemy are tracked and the results sent to the torpedo-director officer, who keeps the directors set, so that torpedoes may be fired at any time. TORPEDO DEFENSE. 426. Personnel of group control parties. — Each group has an independent fire-control party as follows: One officer, spotter. One officer in charge of searchlight control. One range keeper and talker. One petty officer or man to operate distant control of search- light. One spotter's lookout. Each group Is equipped with telephones and voice tubes, each gun and fire-control group having its own circuit. Each has a searchlight assigned to it, and a crew consisting of a man and helper who focus the light and stand by to elevate iind train as necessary in case distant control fails to func- tion. The system is elastic and the eight groups (four on a side) may be combined at discretion. Each group is entirely in- dependent of every other group except as regards salvo sig- nals unless combined. 228 GTTWNERY INSTRUCTIONS. 427. Operation of system. — The chief fire-control officer and assistant fire-control officers are stationed on the bridge. The former gives orders directly to the assistant fire-control officers. These officers wear the telephones. An officer or petty officer operates the master key for controlling the salvo signals, which enable the guns in all groups to fire at the same time. The operator of the master key give* two short rings shortly before firing to "stand by," and a prolonged ring to "fire." During this prolonged ring all guns i-eceiving the signal fire when "on." Attempt is not made to fire all guns simultaneously as this would interfere with accurate shoot- ing. The time of the firing interval is regulated by the chief fire-control officer. The officer in charge of a group receives the order "com- mence firing" from the chief fire-control officer. The group spotter then orders a certain gun of his group to fire ranging shots, the talker passing the word to the gun designated, to- gether with the initial range and deflection. After firing sufficient ranging shots to get on, the sights of all guns being kept corrected, the group spotter orders "open salvo." The order is passed down by the talker to all guns of the group. When order "open salvo" is given the group spotter closes the group key, and the guns of that group receive the salvo signal when the master key is operated from the bridge. In case it is desired to have the guns of a group cease firing, or it is desired to again fire with an individual gun, the group key is opened, and the salvo signals cease and the necessary instructions are sent to the gun or guns over the lines of communication by the group fire-control officer. By this means an individual and elastic means of control is provided. As the spotter for each group sings out a spot, the talker applies it to the range and deflection board which lie holds in GUNNERY INSTRUCTIONS. 229 his hands and passes the corrected range and dellectiou to the group of guns. Each gun should have a standard range and deflection for zone fire, at which sights shoukl be set and maintained when- ever quarters are sounded for torpedo defense, until other ranges and dedectious are ordered. Attention is invited to the advisability of firing short rather than over. CHAPTER 19. ERRORS OF GUNFIRE. The following is a reprint of Ordnance Pumphlet No. 409, of August, 1912, on Dispersion and Errors of Gunfire, witli minor additions : 428. Dispersion, elements of.— On investigation it will be found that all the errors that exist in gunfire may be grouped under two heads: I. Range errors and lateral errors. II. Dispersion errors, both vertical and lateral. I. It is convenient to call the range errors and lateral errors " Fire-control errors," as their values are dependent largely on fire control. Even if it were possible to have no dispersion there would always be fire-control errors. The magnitude of these errors may be obtained from target-practice records. Without discussing these errors it is important to understand that no matter what the dispersion errors are, the fire-control errors should be kept as small as possible to insure the maxi- mum hitting. II. Dispersion errors will always exist. They are due to many causes, the principal of which are : (rt) Variations in the powder, projectile, cartridge case, primer, etc. {b) Variations in the gun. (c) Variations in sight, and mounting. (d) Personal errors of pointers and sight setters. The various elements of these dispersions will be taken up in order. 429. Powder errors: 1. Variation in weight of charge. 2. Variation in temperature of charge. 230 GUNNERY INSTRUCTIONS. 231 3. Variation in density of loading. 4. Hygroscopic condition. 5. Variation in age of powder. 6. Imperfect blending, 7. Variation In indexes. 8. Variation in weight and distribution of ignition charge. 9. Variation in form of charge. 10. Unsuitability of powder. 11. Variation in muzzle velocities. 430. Variation in weight of charge. — A variation in the weight of charge may occasion a large variation in pressure, giving a large error in muzzle velocity. Great care is taken in establishing the correct weight of charges assigned to the various guns. Especial care is taken in the magazines in assembling the weight of charge cor- rectly, but it may happen through some mischance that either the wrong powder or the wrong weight of charge Is used in the gun. Every precaution should be taken to prevent this, as aside from introducing dispersion a small increase in weight of charge may occasion dangerously high pressures. 431. Variation in temperature of charge.— All powder charges are " fixed " at a uniform temperature of 90° F., the temperature closely approximating to that of magizines on board ship. It will be found that if the temperature varies from 90° F. errors will be occasioned in the initial velocity. Tests were conducted at the naval proving ground with 4-inch .50-caliber Mark VIII, 5-inch 50-caliber Mark VI, and 8-inch 45-caliber Mark VI guns, to determine the size of this error. From the appended sketches A and B it will be seen that for small variations from 90° F., a change of 1° F. in the temperature will occasion a change in the initial velocity of about 2 foot-seconds. It is not important that the magazines should be kept at 90° F., but it is very important that all magazines should have 232 GUNNERY INSTRUCTIONS. the same temperature, or that proper allowance be made where temperatures differ. It could -readily happen that one maga- zine was 10° F. hotter than another. This increase in tem- perature will cause an increase in initial velocity of 20 foot- seconds, producing in a 12-inch 2,700 foot-second gun a vertical />/)/ iJ)fAVAL F^ov/j yg (}!?ofy/fD Bl. uEH^inT BiA OF t ')ffDn ANCi - >VJ?. 3ar^9. N^ f4Z May? /9j2 error, at 10,000 yards, of about 35 feet. It is evident that this error is very serious and that every effort should be made to keep the temperatures of magazines uniform. It is important that the temperature of magazines be not only the same, but that the powder should have attained unl- GUNNERY INSTRUCTIONS. 233 form temperature throughout. At the naval proving ground a powder heated 19 hours gave 30 foot-seconds less velocity than when heated 24 hours, although the thermometer in each case registered 90° F. €>KE .TCM B. iV(!¥ ?QL ^^ fS S ^ *tt Ffptf :M" rW TtliM « tr'T 4t *. M tM {4 S Pl ^ -5 ta:-^ ^tP t « • • » ■ ^ ?f 5 :^ s s 9 1 I 5^ V ^'. '^SC CAi rv M L^ k t5. //o. 29. J. Ffn> vf A AV^l F/f& r/N6 2 '■'AfC Blve Fffih r/ii> (5^7 mi ; /?>=- Qf^c. rt'WiV -r A ^, ,-?/ W^.9 432. Variation in density of loading. — In general an in- crease in the density of loading occasions an increase in the pressure and an increase in the initial velocity. With the projectile properly seated and the correct weight of powder charge the density of loading is constant and should occasion no error. 234 GUNNERY INSTRUCTIONS. The density of loading is different in different guns, but no error is introduced tlirougli this cause, as the weight of charge and the density of loading are Interdependent, and any error in the density of loading is eliminated when the charge for a gun is fixed. As. a gun erodes the projectile seats farther down the bore, and a decrease in the density of loading occurs, causing a falling off in pressure and velocity. The density of loading a gun is given by the formula ^^ WX27.68 Volume of chamber (in cubic inches) in which w=weight of charge in pounds. For a long time it was considered that a density of loading of about 0.5 was correct for nitrocellulose powder. It was deemed necessary, in order to secure proper inflammation of the charge, to have considerable air space around the powder. Further experience has shown that much higher densities of loading can be used. It is not possible from present expe- rience to state what the maximum allowable density of load- ing should be. A high density of loading should be avoided with quick powder tis erratic pressure^? are likely to be produced, but if slow powder is used the pressures are re- liable. The following satisfactory densities of loading have been obtained : Six-pounder gun, 0.80 ; 3-inch field gun, 0.77 ; 5-inch .40-caliber gun, 0.72. The greatest density of loading obtained in any gun in service is about 0.G7. In bag guns the density of loading is limited by the design of the powder chamber and the breech opening. To facilitate loading there must be a definite clear- ance between the diameter of the powder bag and the smallest diameter of the gas-check seat. With cylindrical charges for good loading conditions this clearance should be about 0.75 inch, and not less than 0.5 inch. GUNNERY INSTRUCTIONS. 235 The following table shows the effect on pressure and ve- locity of changing the density of loading. Charge. 31 pounds.. 32 pounds.. 35 pounds.. 37.5 pounds 40 pounds.. 6-in?h .50-caliberKun,No. 338, chamber 75.4 cubic inches larger than No. 353. Pressure. Tons. 11.8 13.4 15.3 17.4 19.4 Initial velocity. Foot-seconds. 2,439 2, .567 2,704 2,842 2,984 6-inch .50-ca!ibergun, No. 3-i3, chamber of stand- ard size. Pressure. Tons. 12.6 14.6 16.3 18.9 20.9 Initial velocity. Foot-seconds. 2,488 2,630 2,785 2,949 3,022 433. Hygroscopic condition. — There should be little varia- tion due to hygroscopic condition of powder if the powder is kept in air-tight tanks and is not exposed until shortly before it is fired. As an extreme case, the following test was conducted to show the effect of moisture on the powder charge. The test was conducted in a 5-inch 50-caliber gun, with a weight of charge of 25 pounds. Two charges were dampened by immer- sion in water, the free water being drained off. 5-inch 50-caliber guns (charge 25 pounds). Powder. Dry..., Do Damp. Do Tempera- ture. Pressure. Tons. 60° F. 13.7 60° F. 13.8 60° F. 11.0 60° F. 11.5 Initial velocity. Foot-seconds. |^f,^}MeanI. V.= 2,795. ^•^j^}MeanI. V.= 2,628. 236 GUNNERY INSTRUCTIONS. It should be understood that the foi'egoing test is not com- parable to that of a powder which has deteriorated through exposure to moisture. The test is merely to show the differ- ence in pressure and velocity between wet and dry powder. ' Powder exposed to moisture deteriorates, and of course loss of pressure and velocity depend upon the extent of the de- terioration. The slowing down of the powder in the test referred to is due entirely to the absorption of moisture, and this absorp- tion would become greater with powder in which the vola- tiles were low. 434. Variation in ag'e of powder. — As powder ages it gen- erally loses some of its volatiles and the thickness of the web decreases slightly. This results in making the powder some- what quicker, giving increased pressure, with a small change in muzzle velocity. If all the powder of an index is subjected to the same con- ditions of stowage, however, the change in velocity will be uniform throughout. It is considered that no error is intro- duced by ageing of powder on board ship, provided the powder passes satisfactory tests, althougli the velocity and pressure may differ from that on proof. If the powder should begin to deteriorate, large errors would be occasioned in muzzle velocities, but the tests on board ship would detect this dete- rioration and prevent the use of this powder. The life of powder depends very largely on the conditions of stowage. The average life of an index under fair stowage conditions may be taken as about 10 to 12 years. With stabilized powder the life will probably be 20 years. It is very important that the powder tanks and cartridge cases be kept air-tight, so as to maintain stowage conditions similar. The life of powder is lengthened, too, by keeping the tanks air tight. (See art. 2S03 (1), Naval Instructions, 1913.) 435. Imperfect blend. — Before powder is tested and as- signed to service it is thoroughly blended. It is found in the GTINNERY INSTRUCTIONS. 237 manufacture of powder that the different lots vary slightly in nitration and to some extent in volatiles. Several lots are blended into one Index before being proof fired. The blends give very uniform results, and there 'should be little or no error resulting from this cause. If an imperfect blend were made of widely dissimilar powders, large variations would be obtained in initial velocities, depending upon the dissimilarity of the powders blended and the imperfect blending. These conditions do not obtain, however, in the powders issued to service. 436. Variation in indices. — It should be understood that the foregoing remarks (item 1-6) apply to any one index of powder. The difference in the temperature, age. etc., of any index will produce a variation, but the whole index should be similarly affected. If, however, part of the firing of a gun is done with one index of powder and part with another, there may be introduced an additional eri-or, due to using the dif- ferent indices. With all the care in manufacture and inspection that ob- tains, it is found that it is impracticable to make the different indices exactly alike; in fact, an index is simply the blending of a number of lots of powder. Different indices require dif- ferent weights of charge to give service velocity. In fixing the weights of charge of different indices to give service velocity there is likely to be a small error, which should not exceed, however, about one-half of 1 per cent of the muz.zle velocity. In addition to this error, the different indices may not be similar as regards temperature, age, etc. The use of addi- tional indices introduces more errors. It would be desirable, of course, on board ship to have only one index of powder for each caliber of gun, but this is not practicable. Provision should be made in fire control for using different indices. One index should be exhausted before firing is taken up with the next index. Any variations occurring in the new index could then be compensated for by the spotter. 238 GUNNERY INSTEUCTIONS, 437. Variation in weight and distribution of ignition charge. — There should be no variatioa from this cause in the powders assigned to service. Numerous tests have been conducted to establislt the correct weight of ignition to give proper inflammation. This weight is now standardized for the various calibers of guns. To show tlie effect, liowever, of varying the weight of ignition charges, the following data are given. It will be noted from these data that there is considerable variation in pressure and velocity occasioned by using different Aveights of ignition charge. Ignition charge. 6-inch SO-caliber B. L. R. {same weight of charge through out). 100 grams at breach end of charge Do 3 ounces at each end of charge Do 6 ounces at each end of charge Do 8-inch 33-caliber B. L. R. (charge, 5S pounds). Regular ignition, 14 grains Do Do 7 grains each end of each section— 29 grains in all 1-2-inch iO-caliber B. L. R. {charge, 346 pounds). Ignition at each end of each section Total, 6.92 pounds Usual ignition Pressure. Velocity. Tons. Foot-secondx. 18.85 2,914 18.80 2,907 19.60 2,927 19.50 2.924 19.80 2,922 20.10 2,923 12.03 2,098 12.06 2,108 12.60 2,098 12.06 2,128 17.15 2,754 17.61 2,768 18.25 2,806 438. Variation in form of charge. — There should be no variation from this cause in service, as a definite form of charge is adopted for each gun. Tests have been made at the naval proving ground to determine whether better results are obtained with the charge put up in a large or a smaller num- ber of bags. Little variation in either pressure or velocity GUNNERY INSTRUCTIONS. 239 resulted, however, provided sufficient weight of ignition was added to the charge. 439. Unsuitability of powder. — In general, it is the inten- tion that all powder should be consumed in the gun, but it sometimes happens that unburned powder is blown from the gun. This condition is approaclied in most modern guns in the effort to get a high muzzle velocity without undue maxi- mum pi-essure. It is evident that the same velocity could be obtained with a quicker powder, giving a higher maximum pressure, and this condition tends to give more uniform muz- zle velocities: but the maximum pressures are kept down in the effort to retluce erosion. In all but especial cases, how- ever, the whole charge should be consumed in the gun. It becomes a delicate matter to get a powder that will give the velocity required and still keep below the maximum pres- sure allowed. It frequently happens, too, that owing to the unsuitable design of a gun it is difficult, if not impossible, to select for that gun a thoroughly efficient powder. The selec- tion of the most suitable web thickness is further complicated by the fact that in two similar powders of the same web thickness there may be considerable variation in volatiles, or other characteristics, causing considerable differences in bal- listic properties. 440. Variation in muzzle velocities. — It is found that with conditions as nearly perfect as they can be made there re- sults nonuiiiformity of muzzle velocities. The first round fired may show 2,700 foot-seconds and the next round 2,710 foot-seconds. This variation in velocities results mostly from Ihe nonuniformity of the burning of the powder, although other causes contribute to it, as will hereafter be seen. In general, it may be said that the average variation in muzzle velocity is less than one-half of 1 per cent of the aver- age velocity. If the average of 10 shots gives 2,800 foot-sec- onds, it is not to be expected that the average shot will vary more than ±14 foot-seconds, although particular shots may 240 GUNNERY INSTRUCTIONS. have greater variation. lu fact ± one-half of 1 per cent is about the greatest mean variation of any powder in service. The following table shows the average variation from the mean in the muzzle velocities of a few guns and powders. These variations change with the different powders tested. 14-inch, 45-caliber, 2,600 foot-seconds, mean of 9 sliots, gave ±3 foot-seconds. 12-inch, 50-caliber. 2,900 foot-seconds, mean of 11 shots, gave ±11 foot- seconds. 10-inch, 4()-caliber, 2,700 foot-seconds, mean of 5 shots, gave ±5 foot-seconds. 8-inch, 4.5-caliber. 2,750 foot-seconds, mean of 11 shots, gave ±4 foot-seconds. 7-inch, 45-caliber, 2,700 foot-seconds, mean of 6 shots, gave ±11 foot-seconds. 6-inch, 50-caliber. 2.800 foot-seconds, mean of 24 shots, gave ±8 foot-seconds. The effects at 6,000. 9,000, and 12,000 yards are : 14-inch 45-ealiber 12-inch 50-caliber 10-inch 40-caUber 8-inch 45-caliber. 7-inch 45-caliber . 6-inch sa-caliber. Service. 2,600± 3 2,000±11 I 2,700± 5 ' 2,750± 4 2,700±11 2,800± 8 6,000 9,000 Yards. Yards. 11 16 1 39 56 i 18 26 1 14 19 37 50 25 34 12.000 Yards. 21 70 32 23 60 39 441. Reduced ch.arg'es. — Reduced charges are fixed by se- lecting weiglits whicli at the proving grounds actually give desired reduced velocity. For 12-inch they have hitherto been made up in tin-ee sections instead of four. l)ut with one-third more ignition in each so that the total ignition is the same as for service. The Bureau of Ordnance is considering the ad- visability of making up reduced charges in four sections, with bags of service length, but less girth. This, however, is merely GUNNERY INSTRUCTIONS. 241 H matter of whether the full number of sections is better for drill purposes tluiu getting approximately service weight in each, but with one less section. The velocity would be the same in either case, but there would be the advantage of the larger bag being necessarily closer to the mushroom, and rherefoi-e more certainly ignited. 442. Unconsumed powder. — Powder burns with increasing surface until the holes enlarge into each other. Slivers are formed, some with three concave sides from the inside web. and others with two concave and one convex side from the outside web. These burn with diminishing surface, and this fact (especially since formed when the projectile is moving so fast) makes their contribution to the energy of the projectile relatively quite ineflicieut. In delaying their formation as long as possible, it is sometimes found advisable to use the heavier charge, burn it with inci'easing surface until very late, and let the slivers go. In certain guns, notably Army mortars, this is the rule rather than the exception. Uncon- sumed powder outside of a gun does not mean low velocity because of that amount of powder having been depended upon to burn. It is expedient to use the same web for reduced charges, and in most cases more of it remains unburned than with a full charge. More powder generates pressure quicker, and this pressure in turn quickens the burning enough to burn up an even larger amount of powder. Both service and retluced charges can give no velocity errors because of leav- ing unconsumed powder, for they have been actually fired at the proving ground and give the stated velocities without regard to unconsumed powder. 443. Projectiles: 1. Variation in weight. 2. Variation in diameter of bourrelet. 3. Variation in rotating bands, 4. Variable form of projectile. .'i4776— 18 16 242 GUNNERY INSTRUCTIONS. 5. Position of center of gravity. 6. Projectiles not concentric witli bore of gun. 444. Variation in weight. — Tliere may be a variation in tlieweiglitof the projectiles used. Tlie standard weight of pro- jectiles includes the weight of the bursting charge. The error introduced by firing projectiles of different weights is not very great for small variations. A 12-inch projectile, for instance, 3 pounds overweight, will produce at 10,000 yards an error in range of but 12 yards. This is an error which can be readily eliminated, however, and should not exist. A considerable variation in weight would produce a large range error. 445. Variation in diameter of bourrelet. — The standard clearance between the bore of the gun and the diameter of the bourrelet of the projectile is 0.015 inch for all modern projectiles. Some of the older projectiles have a clearance of 0.05 inch, and these projectiles should not be fired with the later ones. It has generally been assumed that the smaller clearance gives better flight, but the variation to be expected within the small limits mentioned has not been establifhed. It has been shown, however, that projectiles centered by means of a bourrelet give more efficient flight than those which are not so centered, the coefficient of form being reduced by about 5 per cent. 446. Variation in rotating bands. — If rotating bands on projectiles differ either in width, thickness, or form there may be occasioned a variation in pressiire and muzzle velocity. In general, if the forcing is increased— that is, if more copper is to be engraved — there will result an increase of breech pressure and a decrease in muzzle pressure. The error in muzzle velocity may be slight, but in general increased forc- ing will cause an increase in the muzzle velocity. The following tests were made at the naval proving ground to determine the effect of using various types of rotating bands In different guns: GUNNERY INSTRUCTIONS. 243 In a 12-inch 35-caliber Mark II gun having depth of rifling of 0.05-inch projectiles were fired having rotating bands of standard width, but increased in thicliness from 12.12 to 12.17 inches. Tlie cross-sectional increase in copper to be engraved was from 1.35 square inches to 2.47 square inches. There resulted an increase in the pressure of O.S ton. There was little change in velocity. A similar test was held in 12-inch 45-caliber Mark VI gun, in which the depth of rifling was 0.05 inch. There resulted in this gun an increase in pressure of 0.4 ton, causing an in- crease in the velocity of 22 foot-seconds. Tests were also conducted in 14-inch 45-caliber ' Mark I gun, with depth of groove of 0.075 inch. Bands of similar width, but of standard thickness, 14.175 inches and of di- minished thickness, 14.122 inches, were fired. Thei'e resulted a decrease in the standard pressure of about 1 ton, with no change in velocity. A similar test was conducted with 12-inch 50-caliber Mark VII gun, with depth of rifling 0.075 inch. The banris were the same width ; one was of standard thickness, 12.18 inches, and one of diminished thickness, 12.12 inches. The thin band caused a drop in pressure of 0.7 ton, with a loss in velocity ol 37 foot-seconds. Tests of a 6-inch 50-caliber gun, weight of charge 42* pounds, gave the following data : Diameter of band. Pressure. Velocity. Average. Inches. 6.112 Tonn. 13.26 15.30 14.06 Foot-seconds. 2,802 2,810 2,822 Foot-seconds. 6.112 2,811 6.112 6.112 6.135 14.03 16.01 16.04 2,822 2,825 2,843 6.136 6.144 244 GUNNERY INSTRUCTIONS. It should be undei'stood that these tests were held over wide variations ; but as there are in service guns of the same caliber having different depths of rifling, it might well happen that rotating bands designed for one rifling were inadvertently used in guns having a different depth of rifling. If thick and. thin rotating bands were used in the same gun it is evident there might be wide variations in pressure and muzzle veloci- ties. All bands should be gauged to see if they are correct for the guns in which they are to be fired. For 12-iuch guns there are some 12.12" bands in service and some 12.18". Grooves in the guns are 0.05" deep or 0.075" deep except in some special cases. The large bands go with the deep grooves. The dimensions are the body of the band, the lip being still larger. T.arge bands are at present favored because they act as a " shell stop," holding the shell at ap- proximately its right seating even in a worn gun, while with a smaller band the same amount of erosion allows the shell to ram in farther and lose more velocity. From firings in a new 12-inch gun with 0.12" grooves it was found that each one one-hundredth on the band gave an additional 4.8 f. s. from 12.12 to 12.18" and about 4.0 f. s. from 12.18 to 12.25", so, among shell supposed to be banded alike, ordinary tolerances in workmanship can give no appreciable velocity differences. Thicker bands increase the serviceable life of the gun, as steady flight is maintained on a larger number of rounds with the same gun. The action of larger bands is to increase the pressure developed before the shell starts, and as pressure accelerates velocity of combustion the powder is burned earlier throughout than normal. It thus resembles in its action a powder of thinner web and develops additional pressure and velocity more than sufficient to overcome the slightly increased friction of the band. Provided that the bands do not strip and that the muzzle velocity is the same, they can have no effect on flight, because all sizes come out of the gun the same diameter. GUNNERY INSTRUCTIONS. 24a The larger-sized bands often fail to stick in the seat when the gun is elevated, but a single rope yarn around the baud will prevent tleir slipping back. Minor changes in design are being undertaken to overcome this difficulty. 447. Form of projectile. — The form of projectile is of great importance. The outside contour of all the projectiles fired from a battery should be the same. The length and diameters should be alike within the allowed tolerances. The effect of changing the form of the point of the projectile from 2-caliber radius to 7-caliber radius was very marked. There resulted an increase in the range of 16 to 20 per cent, with all the attendant advantages. Tests were conducted giving the projectile a still sharper point, with a radius of 10 calibers. This resulted in a further increase in the range of about 7 per cent. This increase, how- ever, did not offset the disadvantages of the longer point. If projectiles of the same weight are fired with different outside contours there will result wide variations in range. It is very important that all projectiles fired from a battery have the same form. Owing to the changes which have taken place in the de- velopment of projectiles, it may happen that the projectiles supplied a vessel are not all alike. There are always some (lilTerences due to manufacturing toleran< o^ ovon if the pro- jectiles are otherwise alike. 448. Position of center of gravity. — Variation in the fore- and-aft position of the center of gravity will cause variation in range, even although the outside contours of the projectiles are alike. The position of the center of gravity and the force of the resistance of the air determine the overturning moment that a projectile encounters in flight. A change in the posi- tion of the center of gravity will change this overturning moment, and so cause a variation in both range and deflection. It is likely, however, that this error is small for small varia- tions in the position of the center of gravity. Even although 246 GUNNEKY INSTRUCTIONS. the fore-and-aft position of the center of gravity is the same in projectiles, it may be eccentric in the projectiles. Eccen- tricity may be produced by a liidden cavity in the steel, or by a variation in wall thickness. Tests are made to detect any eccentricity, and such projectiles are rejected. Any error caused by a small eccentricity ouglit to be of small magnitude. It will be found that there is considerable variation in the position of the center of gravity due to the changes in the development of the projectile, use of different fuzes, different forms of cavity, etc. 449. Projectiles not concentric with bore of ffun. — It may happen, especially after a gun is somewhat worn, that the projectile's axis is not concentric with that of the bore of the gun. There is always, of course, a slight divergence, due to clearance of the bourrelet diameter, but this may be aug- mented if the rotating band does not center the base of the projectile in the bore of the gun. It is not possible to tell how great this variation is, but it is likely that the projectile rarely leaves the gun with its axis in the exact line of the bore of the gun. CARTBIDGE CASES, PRIMERS, ETC. 450. Cartridge cases. — There may be a slight variation in the capacity of cartridge cases, due to the tolerances allowed in manufacture. This changes the density of loading, and so affects pressures and velocities. The allowed tolerances in manufacture are as small as they can practicably be made, and any error resulting from this cause must be small. In cartridge cases of 5-inch and 6-inch guns, where -the projectile is loaded separately, it has been found necessary to have a mouth cup in the cartridge case to prevent the end of the case from being split or deformed by the powder gas. The fitting of these mouth cups has a considerable effect GUNNERY INSTRUCTIONS. 247 on velocities and pressures. The following data was obtained from firing a G-inch 40-caliber gun, weight of charge 17 pounds : Using a distance piece and a felt wad, and a loose mouth cup, the pressure was 5.5 tons with a velocity of 1,598 foot- seconds. With the charge put up In the usual way with a tight-fitting mouth cup, the pressure was 6.6 tons, and the velocity 1,651 foot-seconds. The effect of the loose-fitting mouth cup was virtually to decrease the density of loading with a decrease in pressure and velocity. The variation shown in this test, however, is greater than may be expected in service, even with loose-fitting mouth cups, as the mouth cup is in general not more than about 1 inch from the base of the projectile, and the decrease in the density of loading, due to the loose-fitting cup, is relatively small. A similar variation may occur in guns of 5-inch caliber and smaller, due to the projectiles not being seated alike in the cartridge cases. No great error can occur 'in this way, how- ever, as when the cartridge case is loaded in the gun the projectile will likely be pushed back to its proper place in the cartridge case. Any unseating of the projectile would cause a decrease in the density of loading, with consequent falling ofE in pressure and velocity. 451. Primers. — There is considerable difference between the speed of primers, the percussion primer being much faster than the electric primer. Tests were- made at the naval proving ground with an 8- inch/.35 gun. using Mark VIII lock. Combination primers were tested by electric firing and percussion primers by per- cussion firing and the time intervals measured. With com- bination primers the interval from the moment contact was made at the primer until the flame issued from the mouth of the mushroom was 0.031 second, averaging four primers. These primers gave intervals of firing from 0.013 to 0.073 second. Two other primers gave intervals of 0.040 and 0.030. 248 GUNNERY INSTRUCTIONS. A similar test in a 6-incli/50 gun gave for an average of 16 primers an interval of 0.044 second. It is believed that this figure is a fair average for electric or combination primers. With percussion primers the interval from the moment con- tact was made at the primer until flame issued from the mush- room gave 0.004 second, as an average of four rounds, the rounds varying from 0.003 to 0.004. Two other rounds gave 0.0044 second and 0.006 second. It is evident from the foregoing that the percussion primer Is much faster than the electric primer, and so far as concerns this point only percussion firing is more desirable than elec- I ric. It will be found, however, in measuring the complete firing interval that the difference between the electric and the percussion intervals is very small, and the flexibility of elec- tric firing makes it necessary in most cases. 452. Firing interval. — The firing interval may be taken as the time from the instant when the pointer wills to fire until the projectile leaves the muzzle. For measuring, this interval has been divided into three parts : (a) Time from instant when pointer wills to fire until closing of firing key has been completed. (ft) Primer interval. {(') Interval from flame issuing from mushroom until pro- jectile leaves muzzle. Item («) was measured at the naval proving ground. The average of five pointers gave 0.179 ; times of firing from 0.138 to 0.236. With a firing key or tripping a sear the interval would evidently be the same whether electric or percussion firing were used. This interval varies greatly, depending upon the per- sonality of the pointer, a slow pointer requiring more than the average interval. It is believed that the value given of 0.179, hov^ever, is a fair average for service pointers. The value of interval (b) has already been stated. The value of interval (c) varies for different guns, but may be taken as about 0.020. GUNNERY INSTRUCTIONS. 248 Adding these intervals, it will be found tlmt the firing Interval for electric firing is about 0.243 seconds, while that for percussion firing would be about 0.203 seconds. It is evident, therefore, that although the percussion primer is ten times as fast as the electric, the gain in the firing in- terval by its use is very small. 453. Guns: 1. Variation in rifling. 2. Seating of projectile. 3. Density of loading. 4. Temperature of chamber, bore. etc. 5. Vibration of gun. 6. Variation in chamber capacity. 7. EUipticity of bore. 8. Shell leaving bore witli its axis inclined. 9. Erratic flight of shell. 10. Short hangfire. 454. Variation in rifling'. — In the guns of a battery it may happen that there is a variation in muzzle velocities caused by some guns being rifled differently from others. The rifling may be of dilTerent twist; the form, depth, and num- ber of grooves may differ, and the amount that the grooves are narrowed at the muzzle may differ. All of these varia- tions in rifling afl'ect the muzzle velocities. There may be an error from 10 to 25 foot-seconds due to this cause. All guns of a battery should be rifled alike, and this condition generally obtains, but the twist of the rifling as well as the form, dimen- sions and number of grooves have been changed at different times for various reasons, and it will be found in a few in- stances that some guns of a battery are rifled differently from others. 455. Seating of projectile. — As guns erode the projectiles seat farther down the bore. There results a decrease in the density of loading, with consequent falling off in pressure and velocity. Tests made at the naval proving ground show 250 GUNNERY INSTRUCTIONS. the loss of velocity to be expected in 8-inch 45-caliber Mark VI guns, and 12-inch 45-caliber Mark V guns, when the distance of shell seating beyond normal is known. The standard shell seating is shown on the drawings, and the distance the shell seats beyond normal can readily be measured, and the de- crease in the velocity of a gim can be estimated. Projectiles used in these tests had rotating bands with lips of 8".36 and 12".30, respectively. If larger lips are used the protectiles will not seat so far down the bore, and a small part of the loss in velocity and pressure is restored. Practically all of this loss in pressure and velocity can be restored by using rotating bands of proper form to compenate for the erosion. So far as accuracy of fire is concerned, it is important only that all projectiles used should be alike, and that in firing, the distance from the face of the tube to the base of the projecile should be he same in the guns of a battery. Sketches C and D show the loss of velocity to be expected in 8-inch 45-caliber Mark VI, and 12-inch 45-caliber Mark V guns. In a new gun there may be a considerable error in velocity occasioned by the projectile not being home. Numer- ous tests have been made to ascertain this error, and it is found that there is a wide variation in the results obtained. It is impossible to state the magnitude of this error, as it de- pends not only on the distance of the projectile from normal seating, but also on the design of the powder chamber, and on the density of loading. Sufficient data has been obtained to show that it is important for accurate fire to have the projectile seated at the same place each time. In general, the projectile not being home causes an increase in the density of loading, with consequent increase in pressure and velocity. In some types of powder chambers, however, and under certain conditions of loading, the increase in density of loading is more than offset by the loss of gas escaping around the pro- jectile, and there results a decrease in pressure and velocity. The error occasioned by the projectile not being home is not so GUNNERY INSTRUCTIONS. 261 apparent at short-range firing, but it causes serious dispersion at battle ranges. The following data is from tests lield at the naval proving ground : 6-inch 50-caliber Mark VIII gun. Shell not home by— Loss pres- sure. Velocity. 2.9 inches Tons. 0.2 .0 .4 1.2 .9 .8 Loss, 3 foot-seconds. 2.9 inches Increase. 7 foot-seconds 2.9 inciies Increase, 9 foot-seconds. 5.5 inches Increase 56 foot-seconds 5.9 inches Increase. 32 foot-seconds. 5.9 inches Loss. 44 foot-seconds. 7-inch/45 Mark II gun, v^^ith shell properly seated, gave a velocity of 2,721 foot-seconds. Shell not home by 4.4 inches, increased velocity 27 foot-seconds. Not home by 5.2 inches, increased velocity 42 foot-seconds. S-iuch/45 Mark VI gun gave a velocity of 2,721 foot-seconds. Shell not home by 0.6 inch caused loss of velocity of 11 foot- seconds. Shell not home by 1 inch caused loss of velocity of 11 foot-seconds. Shell not home by 2 inches caused loss of velocity of 11 foot-seconds. 5-iuch/Mark VII gun. Shell not home by 1 inch caused loss of velocity of 5 foot-seconds. 12-inch/35 gun : Shell not home by 6 inches — loss of velocity 40 foot-seconds. Foreign reports have been received of an 11-incli gun. Shell not home 0.8 inch caused increased velocity of 27 foot-seconds. Sliell not hon\e 41.4 inches caused loss of velocity of 295 foot- seconds with but one-third normal pressure. Smoke rings are not believed to be in any way connected with improper shell seating, because they are not observed when shells are fired purposely unseated at the proving 262 GUNNERY INSTRUCTIONS. Sm£LL SEATINO f^ ^fVC/^eS f'i'i'OW /f£Aff£>VZ) or Tt/BE. 'C $ ^ GUNNERY INSTRUCTIONS. 268 ground, and because they occur oftenest and best with blank charges when there is no shell at all. Greasing the muzzle of a saluting gun is supposed to make them. Bry^ Jlgfo c/. My. ecks e.e/7 i'iree/. ryp •t/.f bto//? sd fi 'CfTi y 'rin^ tcu. te/a /fOfo '. 93 f in w/. /cA c 'un oi '/y S( rv/c ? rv,y iTt USir, a" c^c/a ere/ % TVt "V/c 93 'iN7m. 6i ^s s qy//YC 7^ GffCl/AtO //// •70^ W 50 20 10 ^ 0> 9> O 254 GUNNERY INSTRUCTIONS. The scale of " rounds fired " corresponding to different seat- ings can be found from slietcli D'. 456. Density of loading. — In general as the density of loading is increased there will result an increase in pressure SKtTCH D 1 12" 45 CAL. GUN MARK V. Shell Seating in New 45 Cal Gun Mark V. 87.06' 88 6 9 BO 9 1 9t 3^ SHELL SEATING IN IHCHCS FROM BEAR ENO OF TUBE (- 60 C and velocity. With the standard weight of charge an increase in density of loading could be obtained on board ship only by having the shell improperly seated. Some guns of a battery, GUNNERY INSTRUCTIONS. 255 however, have different makes of breech mechanism, and this may cause a change in the density of loading. With the shell properly seated and the correct weight of charge, there should be no variation in density of loading. As guns erode, how- ever, and the shell seats farther down the bore, there results a decrease in the density of loading, with consequent loss of pressure and velocity. 457. Temperature of chamber, bore of gun, etc. — Nu- merous tests have been made to determine the temperature of the gun and mushroom head after repeated firing. 5-inch/51 gun was fired 20 times as rapidly as possible. Temperature of mushroom after last shot was 275° F. Tem- perature of gun before firing was 98.6° F. 10 shots were fired in a 5-inch/50 gun In 1 minute 18 sec- onds. Temperature of mushroom before firing, 100° F., after firing 196° F. Temperature of chase of gun before firing. 101° F., after firing, 131° F. Temperature at muzzle, 158° F. 29 rounds were fired from a 5-inch/51 gun in 3 minutes 45 seconds. Temperature of breech face, before firing, 82° F. ; temperature of breech face, after firing, 290° F. ; temperature of chase, before firing, 84° F. ; temperature of cha.se, after fir- ing, 162° F. ; temperature of muzzle, after firing, 304° F. A powder charge was placed in the chamber immediately after firing the 29th round. The charge was left ia contact with hot mushroom for four minutes, and it was tlien taken out unharmed. 3-inch/50 gun was fired 25 rounds. Temperature of muzzle before firing was 72° F., and after firing. 234° F. .50 rounds were fired from the same gun. Temperature of muzzle before firing was 95° F., after firing, 378° F. A foreign 3-inch/46 gun was fired 110 rounds rapidly, the maximum temperature reaching 394° F. Most automatic rifles reach temperatures of 700° or more, depending upon the speed and length of firing. It is found 266 GUNNERY INSTRUCTIONS. that cartridfies phiced in these guns, after rapid tire, will fire, due to the heat. So far as concerns the ballistics of the gun it is evident that the heat of the bore will increase the temperature of the powder charge, and so cause an Increase in velocitj'. pro- vided the charge is left for any considerable time in the bore of the gun. With guns fired under similar conditions this error, however, should not be very gx'eat. So far as concerns safety it would appear that little danger is to be anticipated in the firing of large-caliber guns under service conditions. 458. First and subsequent shots. — The first round from a gun will have slightly less velocity than those fired imme- diately afterward. After the second round no increase can be detected, and it was only by persistent averaging for a number of years that a difference between the first two was definitely established. It is about 25 f. s. for the 3-inch, di- minishing to not over 4J f. s. for 12-inch, for which gun it therefore means about 25 yards at 10,000. The effect is greatest in winter and least in summer, the above being year- round averages. NAVY GUNS. Caliter. Num- ber of exam- ples. Num- ber show- ing; in- crease. Num- ber show- ing de- crease. Num- ber show- ing no change. Sums of in- creases. Sums of de- creases. Average differ- ence. 13-inch 3 22 13 22 14 69 39 16 32 /3 /13 10 15 11 43 29 13 28 6 3 7 1 21 8 1 3 2 5 2 2 128 223 98 287 223 975 655 319 907 123 7 les 2 353 118 45 55 -t-42.7 12-inch + 4.5 lOmch -1-7.0 8-inch + 5.4 7-lnch -1-15.8 6-inch -1- 9.0 S-inch -1-13.8 4-inch -H9.0 3-inch -f-26.6 230 165 51 14 3,845 871 -H2.9 GUNNERY INSTRUCTIONS. ARMY GUNS. 257 12-inch 15 17 7 32 25 22 9 9 6 19 17 13 6 7 1 12 8 8 1 1 1 253 324 146 385 306 346 62 96 120 121 99 157 -fl2.7 lO-inch -f 7.5 8-inch -*- 3.7 6-inch + 8.3 5-inch -f 8.3 3-inch + 8.6 113 73 42 3 1,760 655 + 9.4 Leaving out of account the 13-incli. of which only tliree examples occur, it will be seou that the Indian Head records indicate u plus difference which is much greater for small than for large guns; while the Sandy Hook records indicate a plus difference which is about the same for all calibers. However this may be, the evidence seems conclusive that the difference is not svUficient to cdll for any allowance, or indeed to admit of any allowance being made for it. Apart from the effect of the warming round, it has been suspected that it makes a difference whether the bore is dry or oily. According to an English writer, the fouling from one round of black powder caused a velocity loss of 25 f. s. (p. 287 Brynek), but Russian experi)ucnts seemed to show the reverse, that oil in the bore decreased the velocity 36 f. s. in a light gun. The effect is probably much less in 12-inch guns. At Indian Head the results of the fir.st round fired each day from a 12-inch, using always the same powder, were com- pared. There were 32 observations, some with bore oily and others with it dry, and in contradiction to the Russiou experi- ments, the oil seemed to increase the velocity 11 f. s. Since this is less than many of the variations, the results are not to be taken as showing much more than the fact that the differ- ence, if there is one, is very small. 459. Vibration of gun due to droop or flexibility. — It will be found that all guns have a muzzle -droop which can be 34776 — 18 17 258 GUNNERY INSTRUCTIONS. measured. This droop is greatest in the longer and heavier guns, and the amount of gun droops is liuown and recorded. There is not onlj- a droop, but a sliglit deflection to one side in almost every gun. The droop is partly elastic, for when a gun is placed upside down it also droops a certain amount. In almost all cases, however, the greatest droop occurs when the gun is in the normal position. This droop varies some- what from time to time as the stresses in the gun are varied by firing. Note. — As the gun is fired, forces acting in the bore tend to straighten it. and the various forces set up vibrations which cause the muzzle to describe a curved figure to the right and above its position in the state of rest. From proviug-ground data it is also proved that practically all of this muzzle move- ment take place after the projectile has left the bore of the gun and thus has no effect on its flight. There is no doubt that flexibility is undesirable, and every effort is made to re- duce it as much as practicable in designing guns. The droop with wire-wound guns is about twice that of built-up gnus. From all data at hand, it is evident that the only error caused by droop is due to the variation in droop among various guns on board ship. As an example of an extreme case (the Wyom- ing) the variation in droop (between least and greatest) would cause a difterencc in range of 3-5 yards at 10,000, and these are the worst guns in service for droop. Droop varies with life of gun, apparently. Di'oop. Inch. rounds 0. G90 18 rounds ,720 20 rounds .725 44 rounds . 600 70 rounds . G90 Type gun has greater droop than other 12-inch 59-caliber guns. Average droop of 12-inch 50-caliber guns is 0.435 inch. GUNNERY INSTRUCTIONS. 269 Jlaxiniuni droop is about 0.510 inch. Minimum droop is about 0.3G0 incli. 460. Variation in chamber capacity. — There is a sliglit variation in the capacity of chambers of different guns of a l)atter.v. due to the tolerances in manufactiu'e. There may also be slight dillerences in the chamber capacity due to modifica- tions that have been made in the design of the forward slopes of the powder chamber. Further changes in the capacity may lie occasioned by the fitting of different marks of breech mechanisms to the same type of gun. All these changes in capacity produce the same result. If the capacity of the cham- ber has been diminished the density of loading is increased, and there occurs a slight increase in pressure and muzzle velocity. With an increase in chamber capacity the reverse occurs. 461. Ellipticity of bore. — If the bore of a gun is elliptical a consi(k>ral)le error may be caused. A .5-inch 51-caliber JNIark VII gun did not true up at the muzzle during manufacture for about 82° of the circumfer- ence. The diameter of this part of the muzzle was 0.010 inch too great, running to 0.003 inch at 21 inches from the muzzle. This gun was hred with an exactly similar standard gun at a range of 850 yards. The powder and all other variables were alike in the firings. The standard gun was tired five times and g;:ve the follow- ing errors at 850 yards: Mean vertical error, 4.68 inches. Mean lateral error. 4.98 inches. The elliptical gun was fired six rounds at the same range and gave the following errors: Mean vertical error, 14.46 inches. Mean lateral error, 13.42 inches. Similar results were olitained in the test of a 3-inch 50- lii liber gun. the muzzle of which had one diametd' O.OOS inch too great. 260 GUNNERY INSTRUCTIONS. As guns erode it is found tiiat tlie bores are worn more or less elliptical. In general it will be found that tlie greatest diameter (facing tlie muzzle) is tlie one running northwest and southeast tliis diameter for riglit-handed twist being in general slightly greater than the vertical diameter. The least diameter is the horizontal one. A 12-inch 45-caliber Mark V gun, after tiring 183 rounds, showed on star gauging that the vertical diameter was 0.036 inch greater than the horizontal at the origin of rifling. At the muzzle the vertical diameter was O.OIG inch greater than the horizontal. If all guns of a battery were fired the same number of rounds it is likely that little error would be introduced by ellipticity, as all guns should Avear in the same manner. 462. Projectile leaving bore with its axis inclined.— It is likely that a projectile never leaves the bore of a gun with its axis in the exact line of the bore of the gun. There occurs an initial angular deviation which may be in any direction. The bourrelet diameter of the projectile is very close to the diameter of the bore of the gun, and this error in modern projectiles should be small. Owing to the fact that the gun starts to recoil before the projectile gets entirely clear of the bore, there may be an addi- tional deviation given to the projectile by the jump or the vibration of the gun. There may be a still further deviation occasioned by the nonsymmetrical escape of gas as the pro- jectile leaves the muzzle. It is impracticable to ascertain the extent of these errors, howevei*. 463. Short hang-fire. — No variation sihould be occasioned by short hangflres, provided the pointer maintains continuous ;iini. If the hangfire is of considerable duration, however, even while maintaining continuous aim, there may be an error introduced owing to the fact that the vertical and hori- zontal speed of displacement of a gun may be different from that existing when the other guns of the battery were fired. GUNNERY INSTRUCTIONS. 261 464. Erratic flight of shell. — It occnslonally happens that a sliell will prove erratic in flight. In the case of new guns this defect is generall.v to be found in the banding of the projectile. The baud uiaj- be either stripped from the pro- jectile or sheared. In either case the projectile does not get correct rotation and erratic flight or even tumbling may occur. In the case of eroded guns the rotating band has to with- stand much heavier sti'esses. and there comes a time in the life of the gun when tlie rotating band is unable successfully to withstand the excess stress. The rotating band is gener- ally sheared before the projectile leaves the gun, and as the projectile gets little or no rotation, tumlfling and erratic flight will occur. Correct flight can generally be restored by using rotating bands of augumented dimensions. This method is not practicable, however, for any extended series of firings. 465. Muzzle movement. — Recent determinations of the muzzle movement during recoil made by tixcd markers scrib- ing on horizontal and vertical plates secvu-ed to the muzzle of a 14-inch gun shows that the total vibration is over an inch. Nothing happens until the shell is well clear. The droop is § to i inch in 12-inch 30-ca liber and 14-inch in 45-calib(?r guns, and evidently, from the above, the shell nmst leave a curved bore taking the direction of the final tangent. A great num- ber of firings at plates 850 feet distant show that the droop is greater than that calculated from the trajectory by ap- proximately the amount needed to corroborate the above rea- soning. The droop exists when the projectiles are ranged, and such values are selected for the coefficient of form as will make range tables agree with actual firings, so that average natural droop, unless variable, is eliminated. When guns are langed at the proving ground, the quadrant is on the stiff l)art of the bi-eech ; afloat they are elevated with reference to the line of bore sight, which is a sort of chord. This has the effect of making guns afloat shoot just a little further, which effect, however, is, if anything, desirable in making up for the small loss in range that the wear causes. 262 GUNNERY INSTRUCTIONS. 466. Heating of the gun.— If the top of a gun is heated more than the underside, due to exposure to sunlight, the effect of unequal expansion is to make the gun curve down- wanl a\\n.v from the sun. According to a British ordnance writer, the top of a gun is 3.6° F. warmer in summer and this may even reach 7.2° F. in the Tropics. He calculated for British 12-inch 50-caliher guns that the droop is affected 0.010 inch per degree Fahrenheit. As the total temperature difference in summer is less than 3.6° F., it could not be more ihan part of this between different turrets boresighting at the same time, and droop could not be affected more than a few hundredths of an inch at most. (From article in Journal of United States Artillery No. 107 (p. 73), 1° C.=47^ therefore 1° F.=0.47'x|=0.26 minute, and (p. 64), 0.092^^=2.35 minutes; therefore 1° F. =0.26X^^=0.0102 inch.) The only sights that temperature changes should affect are certain of the ohler ones where the parallel motion mechanism is partly of brass and partly of steel, hut the calculated error in these would be very small. 467. Effect of change of temperature on straightness of guns.— Experiments have been recently made at the proving ground to obtain data related to the effect of sunlight on the straightness of guns. As a result of three experiments, it appears that consideriug other unavoidable causes for varia- tion that due to change in temperature may usually be ne- glected. For instance, in the case of a 12-inch 50-caliber gun, pointed south, between 11.45 a. m. and 3.45 p. m., with a maximum temperature at 2 p. m. of 94° F., the change in range did not exceed 25 yards. Tlie maximum variation through the 24 hours was shown by the ellipse, 5 minutes high, and 9 minutes wide (see experiment No. 2), which corresponds to 125 yards' range, and 29 yards' deflection, at 10,000 yards. With the gun tested, there was but little deviation before 7 GUNNERY INSTRUCTIONS. 263 a. in. The deflection maxima toolv place at 10 a. ni., and 4.30 p. m., and the droop maximum at 1.30 p. m. The movement was faster in the evening tlian in the morning, and scarcely anything after 8 p. m. It is not kown whether or not the heat from firing a round or two is sufficient to cause these effects to disappear. To see if there was any possibility of there being a difference between the action of turret guns, where the breech is covered, and guns on the proving ground battery, where the whole gun is exposed, a 24-hour droop record was made with an 8-inch 45-caliber gun uncovered, and again with a tarpaulin over the breech. There was no practical difference, although examin- ing the records critically, the one with the breech covered was perhaps very slightly larger. The gun faced north, and the record was much smaller than for 12-inch, the dimension being approximately itj-inch eacli way in both instances, or about one-third as large as for the 12-inch. Briefly, the experiments were as follows : Date. Gim. Maxi- mum tempera- ture. Gun pointed. Remarks. July 4, 1913 June 28-39, 1913. June 19,1913 12-in?h. 50-caliber 12-in3h, 50-caliber 12-m:'h, 35-ca'iber 'F. 96 94 South... ...do ...do Selfrepording device en muzzle; the p^Lnt tra'^ed an el- lipse 0.35 in:h wide by 0.25 in :h high. Te.es?fpe rn muzzle sighted rn s reen 316 feet away. C'l mputed cur\ e at muzz.e was irregu- lar, n't cicsed, and was 0.56 in:h wide by0.3Sin'hhigh. Te.esjfpe en nnizz'e screen 327 feet away, t omputfd cur\e irregular 0.21 inch wide ty 0.11 inch high. 264 GUNNERY INSTRUCTIONS. 468. Sight and mounting: 1. Drift error. 2. Sight error anfl telescope error. 3. Mount error. 4. Jump. n. Weather variations. 6. Trunnions not horizontal. 7. Movement of mount due to pitch and roll. 5. Motion of target. 9. Firing through powder gases. 469. Drift. — The drift of a projectile varies with tlie initial velocity, form of the projectile, finnl twist of ritling. angle of elevation, etc. Owing to tlie fact that it i.'; not possible to give the exact values to the weather variations tliat obtain during a firing, it is not possible to give more than an approximate value for The drift, although this value should be within small limits. It is known, therefore, that the drift used in graduating sights is slightly inaccurate, but it is within as clo.se limits as are practicable of attainment. The drift is not of great impor- tance so long as all guns firing are of the same caliber, but when different calibers are fired togetlier variations in the drift may produce lateral dispersion \inless means are pro- vided for bringing tlie calibers together. Fortunately, in high- power guns the amount of drift is small until the longer ranges are reached. A 12-inch 2,700 foot-seconds gun has a drift of but 13 yards in 7,000 yards, but at 10,000 yards this drift becomes 32 yards. At the longer ranges, therefore, care should be taken in firing different calibers of guns together to see that lateral dispersii>n is not introduced by inaccuracy of drift. 470. Sight error and telescope error. — There is an error in all sights. This should be measured in dry dock and be re- corded in minutes of arc. In guns having sights attached to GUNNERY INSTRUCTIONS. 266 slides most of the sight error is caused by the distoi tioii ur spring of tlie parts of the sights or by lost raotioii or improper installation. In turi-et guns liaving parallel motion sights there may be an additional error caused by the arms not beina: parallel in the different positions of elevation of the gun. It is. of course, highly desirable that this error in sights should be reduced to a minimum, as accurate long-range fir- ing can not be expecteil without accurate sights. There is always the possibility that sights may be im- [iidperly graduated either for range or deflection, but these graduations are made with extreme care, and inaccuracies fi-oni this cause are hardly possible. If desirable, however, these graduations can readily be veritied when the ship is in dry dock. Errors in telescopes may be occasioned by parallax or by the parts of the telescope being deranged. Owing to the strong construction of telescopes, however, the parts are not liable to much derangement and parallax can readily be avoided. 471. Mount error. ^Tliere is a limited amount of tiexibility in every mount, and it is possible that the gun does not as- sume quite the same direction relative to the .slide each time on returning to battery. The clearance between the gun and the slide is very .small, however, about 0.02 inch on the diameter, and this error must be insignificant. All guns are balanced, usually slightl.v breech heavy, so that the bearing conditions should be the same after each shot. 472. Jump. — Jump is the increase of the angle of departure resulting from angular motion of the gun i)i the vertical plane caused by firing. The angular motion comes partly from the recoil of the gun (which moves to the rear, various distances up to about 2.7 inches, according to the calibei*, before the 266 GUNNERY INSTRUCTIONS. projectile leaves The muzzle) and partly from elastic yield- iug of the mount or the support for the mount. It is as- sumed that the support for the mount is sufficiently rigid and that any jump will be occasioned by the yielding of the mount. The conditions at the proving ground and those on board ship are quite different. At the proving ground the supports for the mount are rigid, and any jump occurring is due to the yielding of the mount. It is generally assumed, too, that the jump is the same at all angles of elevation, and at differ- ent angles of train, though it is evident that there may be more or less variation from this, depending upon various con- siderations. The value of the jump, whether at the proving ground or on board ship, is very small. It is so small, in fact, that it is difficult to measure it at the proving ground and impracticable of measurement on board shijj. The jump at the proving ground is, in general, not more than two or three minutes of arc. It is likely that on board ship this value is not greater than five minutes of arc. In a 12-inch, 2,700-foot-second gun there woidd be occasioned, at 10,000 yards, an error from this cause of a))out 100 yards. It must be understood that this jump would not produce dispersion unless it varied from round to round, and varied in the different guns. It is evident, therefore, that with properly designed mounts, which are well supported on board ship, the error due to jump is not of great consequence. In addition to the jump in the vertical plane, it is likely that there may be some small lateral errors occasioned, but these may be neglected. 473. "Weather conditions. — It will always be impossible accurately to state the effect of the weather on firing. It is impossible to obtain accurate values for the force of the wind and the readings of the barometer, thermometer, etc.. in the different parts of the trajectory of projectiles, and the state GUNNERY INSTRUCTIONS. 267 of the science is such that even, were the cori-ect values known, their effect on the trajectory could only be approxi- mated. In any particular firing all that can be done to niininiize weather variations is to select conditions as favor- able as possible, and to fire rapidly .several shots, taliing the mean result of the firing. The range tables and books on exterior ballistics furnish the best information available of the effect of weather variations on tlie trajectory. It is evident, however, that the weather variations may produce dispersion, even were all other varia- tions eliminated. 474. Trunnions not horizoutal. — It has been found that .some miiunt.-^ in a ship are jtlaced with the axes of their ti'unnious at angles with one another. In all new vessels it h: prescribed that the axes of the trunnions shall not diverge more than 1.3 minutes of arc from parallelism to a common horizontal plane. Even with mounts correctly installed with their trunnion axes parallel to a common horizontal plane it may happen that the guns are fired in a seaway with the trunnion axes considerably inclined to the horizontal. The effect of this is to introduce a lateral error, which may be right or left, depending upon whether the ship is pitching or 'scending. If the guns are elevated 3° from the horizontal and fired while the ship is pitching 3° there will be introduced an error of sin. 3°Xsin. 3° (tS? by t^^) =1/361 of the range. At 7.000 yards this causes a lateral error of 19 yards. At longer ranges (greater elevations) or with greater pitches this error increases. It will be noted that if the ship had been 'scending the salvo wotild have struck 38 yards from the first impact. There is also introduced a small vertical error, but this is •vf slight importance. It is important that all mounts have their axes parallel to a common horizontal plane and that the guns be fired each 268 GUNNERY INSTRUCTIONS. liin<- with this pl:me relatively at the same angle to the horizontal. 475. Movement of mount due to pitch and roll. — Should a suii be fired even while niaiiKaiiiiiijr perfeet ooniinuon.s aim there is an error introduced due to the actual vertical dis- placement of the mount caused by rolling or pitching. The pitching error is greatest as the speed of the vertical displace- njent due to pitch is considerably greater than that caused by roll — probably about four times as great. It is also evi- dent that the guns in the ends of the ship are affected the most by the pitch and that the guns mounted farthest out- boa i-d are affected most by the roll. In this connection it is important to note that center-line mounting of guns is very desirable as the vertical displace- ment of these mounts is inappreciable for small rolls of 2 or 3 degrees on each side of the vertical. The error due to a roll of 2 or 3 degrees would be not more than a foot on a target at 7,000 yards. For a 3-degree roll the 8-inch guns mounted outboard on battleships of the Connecticut type would have an error on a 7.000-yard screen of about 6 feet, provided the guns were fired in the middle of the roll. If some of the guns were fired in the middle of the down roll and others in the middle of the up roll, the impacts would be separated 12 feet on a 7,000-yard screen. This error, due to trunnion displace- ment, is really the component of the trunnion motion acting on the motion of the projectile, and of course the error in- creases with the time of llight. There is also a sliglit lateral error introduced by the lateral displacement of the trunnion. 476. Motion of targ-et.— It is evident that the vertical mo- tion of the target must be taken into account. If a 27-foot target, at a range of 7,000 yards, is fired at with a gun having a mean vertical error at that range of ±10 feet, the percent- age of hits would be 71.7. If, liowever, the target has a verti- cal motion of 5 feet above the mean and 5 feet below the mean GUNNERY INSTRUCTIONS. 369 position, the probability of hitting is reduced to 67 per cent. The motion of rlit; tarwi lias tlie virtual effect of increasing the mean error of the gun about 1 foot. With greatfv motion of the target the probability of hitting is fui-ther reduced. 477. Firing through powder gases. — Should a gun tire through smoke or gas or .it a time when the strata of the air «s Sketch E. between the gun and taiget are of unequal and varying densi- ties, refraction will take place and accurate shooting is im- possible. Most of the gas which is discharged from the gun is heavier than air and therefore causes a bending of the rays of liylit toward norma!. Tf the gun is entirely surrounded •~>a. Sketch F- by gas. the projectile \vU\ go high, as may be seen from sketch E. Target will be seen along G-A when it should be along G-T. If, hov.ever, there is a volume of air on each side of the re- fra( ting gas. the projectile will go low, as shown in sketch F. 270 GUNNERY INSTRUCTIONS. The error caused by this refracting gas and the strata of air at different densities is very considerable. From data ob- tained at 1,600 yard elementary practice where tlie gun was ready and tlie target tired at as soon as the gas thinned so that the target was visible, it is known tliat the error at 7,000 yards, caused by firing under similar conditions, would be about ±25 feet on the vertical screen. This error is so serious that it nmst be avoided wholly in order to permit accurate shooting. 478. Personal errors of pointer and sight setters. — Tliere will always be personal errors of pointers, some of wliom will fire when eitlier the vertical or horizontal wire of the tele- scope is not on the target, and dispersion, both vertical and lateral, is introduced. Dispersion will also be introduced if tlie sight setter, due either to personal error or bad trans- mission, sets the sights incorrectly in i-ange or deflection. If the angular error of pointing is known, the dispersion due to this cause can readily be obtained from the range tables. Due to some individuality of gun, sight, or mounting there may be a definite constant error for a particular unit, this i-.vvov being either vertical or laterul. Were it possible to eliminate all olht-r sdurces of error this constant error could be detected on calibration; but it is evident that so many errors are present in every firing, and such a large number of rounds would have to be fired to get a satisfactory average, that none but very large errors could be found by calibration. There is no reason to believe that the constant errors of ;:uns and mounts, even if they do exist, are of large magni- tude, and there is no way of detecting them without expend- ing large quantities of ammunition and eliminating all other errors. It is practically impossible to predict, under any given con- ditions, the dispersion that will occur on firing. If correct values could be assigned to the various elements producing dispersion, the probable dispersion would be obtained by tak- GUNNERY INSTRUCTIONS. 271 Ing the square root of the sum of the squares of the various elements. It is not practicable to make more than an ap- proximation to tne value of most of these elements. The only practicable way of obtaining dispersion data is to cal- culate li-om a serieb of firings the dispersions that were ob- tained. With data on the dispersions of a number of guns, under different conditions and at different ranges, it is possi- ble to estimate roughly the dispersions that will be obtained under any given conditions. CHAPTER 20. REWARDS AND SCORES. 479. Battle efficiency pennant. — After the end of the com- petition year the battle-efficiency pennant will be awarded to the vessels of the battleship, torpedo, and submarine classes obtainini^- the highest combined final merit in both gunnery and engineering in their respective classes. The weights of the various forms of practice with guns and torpedoes for the year, and the method of combining gunnery and engineering, are included in the annual rules. Before combining the merits of gunnery and engineering oach will be reduced to a scale of 100.000; the ship attaining the highest merit in gunnei-y or engineering in the class will, for purjvtses of combination, be given 100.000, and the merit of the other vessels will be scaled accordingly. It is probable that the President may send a letter of com- mendation to the commanding officer of the pennant winner of the battleship class. Those officei-s, not to exceed nine in number, who, by their continued efficient work, have been directly responsible for the winning of the battle-efficiency pennant, will if recom- mended by the commanding officer, have a copy of the Presi- dent's letter placed on file with their records. 480. Gunnery trophy. — By direction of the President of the United .States the dej)artment offers trophies for excellence in naval gunnery to five classes of vessels. All forms of practice for the year are given weight in determining the final merit for the various classes. The trophies are awarded at the end of the competition year, July 1. 2-<2 GUNNERY INSTRUCTIONS. 273 The hattloship class inclinles all vessels carrying turrets. The torpedo class includes all tui-pedo boats and destroyers. The submarine class includes all submarines. The cruiser class includes all vessels carrying 5-inch or liirger guns, but not having turrets. The gunboat class includes all vessels, except torpedo craft, carrying no guns larger than 4 inches in caliber. When a trophy is received on board a winning vessel there shall be appropriate ceremonies. Should a vessel holding a trophy be placed out of com- n)ission the trophy will be returned to the department. Letters commending efficiency in gunnery will be issued to officers deemed worthy of such distinction. 481. Battle inefficiency. — The time has arrived, in the de- velopment of combined gunnery and engineering efficiency. when generally speaking, there is no good reason why great differences in the combined final merits for tlie year, should exist among the ships of the same type. Among ships that have performed similar duties, when one ship falls markedly below the other ships of the same type, in the final merit for combined gunnery and engineering for any one year, there have existed inefficiencies in discipline, organization, training, or routine, to cause such a failure. In battle no amount of explanation can compensate for a failure to steam or a failure t< hit. THE NAVY E. 482. By whom worn. — In order to distinguish the members of turret, gun. and torpedo crews that do exceptionally good work, the members of these crews will wear a white E on tlieir blue uniforms and a blue E on their white uniforms, as specified in the uniform regulations. The members of the crew who are authorized to wear this mark of distinction will be designated by the department. 34776—18 18 274 GUNNERY INSTRUCTIONS. their names -will be published in the report of the practice, and they will wear the E until the completion of the next elementary jiractice. In determining the men entitled to wear the distinctive mark for excellence in gunnery, the turret and handling- room crew will be taken as a unit, not the turret-gun crews only. In determining the men entitled to wear the Navy E for excellence in torpedo work, the torpedo crews in the same torpedo room on battleships and armored cruisers will be taken as the unit, and on torpedo and submarine craft the torpedo crews of the vessel will be taken as the unit. 483. How supplied. — When the list of men entitled to wear the Navy E is published, sliips on which they are serving will be supplied, without charge, with a sufficient number of both blue and white E's for the use of the men entitled to wear them. If a regular ship's tailor is allowed the ship he will be required to sew these marks on without expense to the men. 484. Limit of wearing. — The commanding officer will have all the Navy E's worn by members of the crew for the pre- ceeding year turned in and destroyed upon the completion of the elementary practice. 485. Where painted. — Winning turrets, guns, torpedo rooms, or torpedo tubes shall have one block letter E not more than 18 inches high painted on them in a conspicuous place. This E for the preceding year shall be removed upon the com- pletion of this practice. PRIZES. 486. Appropriation chargeable. — For a fiscal jear all prizes for Navy crews will be charged to the appropriation "Gunnery exercises," for that year, all prizes for the Marine Corps to the appropriation "Pay, Marine Corps," for that year. GUNNERY INSTRUCTIONS. 276 487. Value of prizes. — First, second, and third class gun- nery prizes will be issued to meritorious crews, and the prizes awarded them will he made known as soon as possible after the completion of a form of practice. «The present value of prizes is as follows: First prize $20 per man. Second prize $10 per man. Third prize $5 per man. Men entitled to prizes.^Every member of prize crew, in- cluding the turret mijtain. gun captain, gunner's mate, and electrician, whether regular oi- supernumerary, is entitled to a prize, unless absent through fault of his own. A man stationed with more than one prize crew shall re- ceive but one prize. This shall be the highest prize awarded to a crew with which he is stationed. CHAPTER 21. GUN POINTERS AND TURRET AND GUN CAPTAINS. 488. Gunnery and torpedo recgrds. — The instructions for keeping suunery and torpedo records .>^liall be closely fol- lowed. GUN POINTERS. 489. Pointers that fire. — No pointer shall fire at elementary practice unless it is probable that he will be on board at the next form of battle practice. 490. Pay of gun pointers. — See Navy Regulations, 1913, 4442 (11) and 4427 (19). 491. Assig-nment of gun pointers to other duty, restric- tions against. — See Naval Instructions 2501 (2). . 492. Optical examination of gun pointers. — See Naval In- structions, 2501 (3). 493. Pointers must serve at class of gun at which they qualified. — Attention is invited to the provision of the execu- tive order which specifies that a gun pointer shall receive extra- pay only when duly qualified and regularly detailed by the commanding officer and serving as gun pointer at a gun of the class at which he qualified. Thus, if a secondary gun pointer or an intermediate gun pointer is stationed as a pointer of a heavy gun, he must serve in such capacity with- out extra pay until he qualifies at the heavy gun on the next form of practice at which the department directs that point- ers will be qualified. He does not, however, thereby re- 276 GUNNERY INSTRUCTIONS. 277 linquish his qualification as intermediate gun pointer or secondary gun pointer by reason of his employment at a heavy gun. The above does not apply to a pointer shifted from one type of gun to another of the same class. 494. Qualifications. — Gun pointers will be qualified in ac- cordance with the standard determined by the department for this practice. The commanding officer will authorize the extra pay allo^\•ed to such men as are qualified regular gun pointers upon receiving the notification from the department. If there is any doubt about a pointer's allowed score the matter will be subiuitted at once to the Navy Department for decision, with recommendations both of the umpires and the ship's ofl^cers, and that pointer's gunnery record will not bo filled out until the score is decided. 495. Recoinmendations for special qualification and change in a pointer's qualification. — All changes in qualifica- tions of pointers shall date from the day on which the practice allowing pointei'S to qualify is completed. In order to prevent manifest injustice to pointers, as, for instance, where the fire-control party is at fault or sights are out of adjustment, etc., umpires and commanding officers, will report all such cases, giving full details, so that the depart- ment may take final action in the matter. 496. Qualified pointers not stationed at guns. — When a qualified pointer has been removed from his position as pointer of a gun by order of the commanding officer, and is present on board ship during the practice at which pointers are allowed to qualify, he shall, so far as his qualification is concerned, be considered as having fired but failed to qualify ; but this rule shall be applied only in case the pointer was removed for a cause affecting his skill as a pointer. Pointers of interme- diate or secondary gims that have received training and have been qualified on larger vessels may not be fitted for such positions on small craft having an irregular, quick motion. 278 GUNNERY INSTRUCTIONS, There should be no hesitation in substituting unqualified can- didates for qualified pointers in cases where inaptitude is evi- dent. 497. Duration of qualification. — Pointers are I'equired to qualify at each practice allowed them for qualification. A gun pointer's qualification shall last until the next opportu- nity for qualification, pi'ovided this occurs within two years. If no opportunity occurs for renewal, his qualification shall expire two years after the date of the practice at which the pointer qualified. 498. Absence of pointer through his own fault. — A pointer who fails to fire at such a practice through a cause due to his own fault — as, for example, wlien absent without leave — shall be considered as having fired, but failed to qualify, and his qualification shall be void after the date of completion of the practice of his ship, and this fact shall be entered on his gunnery record. 499. Absence of pointer not his fault. — A pointer who fails to fire at a practice where he is allowed to qualify through no fault of his own — as. for instance, where a pointer is duly excused by the commanding officer (on the recommendation of the medical officer) and does not fire on account of his physical condition — shall retain his qualification until two \ears from date of the completion of the practice at which he last qualified. 500. Extra pointers. — When a regularly qualified pointer is serving on board a ship as an extra pointer and has no op- portunity to fire for qtuilification, the practice shall be con- sidered, in so far as concerns the qualification of this par- ticular pointer, as not having been held ; but, as elsewhere specified, lie shall draw his extra pay only when actually per- forming the duties of gun pointer. 501. Reenlistment of qualified gun pointer. — A qualified gun pointer reenlisting for four years within four months from the date of his discharge, and regularly detailed as a GUNNERY INSTRUCTIONS. 279 pointer at a gun of a class at which he was qualified at the time of his discharge, shall be entitled to tlie corresponding extra pay during the unexpired portion f)f Ihe period of his qualification, the interval of time between the date of his discharge and reenlistnient to be included in this period. 502. Employzneflt of qualified pointers. — The sole object of the above rules is to create a class of gun pointers that will be as nearly permanent as possible. Pointers may be removed for any cause affecting the efficiency of the battery, and of this the connnandiug officer will be the sole .judge. It some- times happens. that men whose scores entitle them to a quali- ficatitin as gun pointer by the standards fixed by the depart- ment Miay be considered by their officers as inferior to other men available for the position. There should be no hesitancy ill removing such a man when the efficiency of the ship will thereby be increased. In case any regularly qualified gun pointer on board any vessel is not regularly assigned as a pointer of a gun of the class in wliicli he has qualified, or is removed from his station at a gun, it is directed that the fact be at once reported to the department. If the fact that the man is not employed is due to the lack of a vacancy in the class of gun at whicli he has qualified, the commander in chief of a foreign station should immediately transfer the pointer to anotlier vessel where he can be utilized, and so state in forvi'arding the letter. No qualified gun pointer stationed at a gun which is likely to be used shall be landed as a member of the ship's landing force. In no ease shall a man's conduct or any other consideration except his efficiency as a pointer be permitted to affect liis assignnient as a gun pointer or to influence his removal from that station. 503. Turret training' pointers. — In turrets two men will be detailed as training pointers. The training pointers so 280 GUNNERY INSTRUCTIONS. detailed will act as sight setters for each other, when prac- ticable, and the first and second pointers (elevating) will similarly act as sight setters for each other. Oi'diuarily at elementary practice the training pointers will each train for cue of the pointers at each gun, and the score of the turret run for which he trains will be taken as hft score in consider- ing his qualification as training pointer. In case on^ or more of the pointers for whom a training pointer trains makes a low score that is manifestly not due to a fault on the part of the trainer, a special report of the circumstances will be con- sidered by the department in awarding the training pointer his qualification. 504. Training pointers in superposed turrets. — FV^r the purposes of elementary practice there will be four men de- tailed as training pointers in each superposed turret. Two of these training pointers will train for the eight-inch guns and the others for the twelve-inch, as in double turrets. 505. Training pointers' extra pay. — Training pointers will receive extra pay under tlie same conditions as elevating pointei'S. TURRET AND GUN CAPTAINS. 506. Assignment of turret and gun captains to other duty, restrictions against. — See Naval Instructions. 1913, 2501 (2). 507. Pay of gun captains. — See Navy Regulations. 4427 (20) and 4442 (11). 508. Acting appointments as tuiTet captain, first class, and chief turret captain. — (1) Acting appointments as turret captains to fill vacacies in the complement will not be issued until after the candidates have been examined and recom- mended by a board of officers, the examinations to be held on board the ship to which the candidates belong. Permanent GUNNERY INSTRUCTIONS. 281 appointments and advancement will be governed by the same regulations that apply to other petty officers, but turret cap- tains, first class, may be given acting appointments as chief turret captains only after passing a satisfactory examination of the same character as for turret captain, first class, but of a moi-e advanced nature. (2) Commanding officers will select candidates that appear to possess the necessary qualifications from intelligent men of mechanical bent and good promise as lending men and will have them detailed to the turrets for training in the duties of turret captain for a period of at least three months. After this probationary training the names of those who are con- sidered desirable candidates will be sent to the commander in chief, or to the squadron or division commander, who will order their examination before a board which he shall ap- point, to consist of n6t less than three officers, the majority of the board to be turret officers detailed from a ship or ships other than thc»se on board which the candidates are serving. When practicable at least two candidates, but preferably more, will be nominated for each vacancy in the complement in order that the examination may be competitive. The candidates who pass the examination will be eligible for acting appoint- ments as turret captains, first class. (8) In no case will an acting appointment as turi'et cap- tain, first class, or chief turret captain be given unless the examination of the candidate shows that he is not only thoroughly familiar with the safety precautions to be ob- served in the service of the guns and the method of procedure in the case of a failure to fire, but also that he has been suf- ficiently drilled to make instant application of his knowledge and that he is competent to take full charge of the turret at target practice or in action In the absence of the turret officer. (4) A candidate for appointment as turret captain shall be required to demonstrate his ability before the board by 282 GUNNERY INSTRUCTIONS. actually drilling turret and handling-room crews, preparing a turret for target practice or action, operating all the mech- anism, shifting of gas-check pad, going through the procedure in case of a failure to tire, and in other ways showing his practical ability to meet the various conditions and require- ments in the care and handling of a turret. In regard to qualifications that can not be practically demonstrated the candidate will be closely questioned by tlie board orally, in order that the readiness of his knowledge may be ascertained. (5) The following headings are given as covering the sub- jects on which the candidates for appointment as turret cap- tains shall be examined (in the report of examinations these subjects will be referred to by letter only) : A. Ability to station and drill the turret and handling-room crews. B. Ability to prepare the turret for aftion. C. Dexterity in the operation of all the mechanism of the turret. D. Familiarity with such details of the care of the turret mechanism as come under the cognizance of the gunner's mate of the turret. E. A thorough knowledge of the safety precautions to be ob- served in the service of the guns and of the method of pro- cedure in case of a failure to fire. F.i Ability to bore sight the guns and adjust the telescopes. G. Ability to shift and adjust a gas-check pad and breech mechanism. H. A ready knowledge of how properly to direct changes to be made in the compensation for range and lateral errors, in order to bring the shots on the target again after they have begun to fall oft'. I. A thoi-ough knowledge of the firing circuit, with ability to detect and remedy local defects. J. Ability to fill the recoil cylinders and a thorough knowl- edge of the lock. GUNNERY INSTRUCTIONS. 283 K. A knowledge of the care aud preservation of tlie shell rooms and magazines and of the various powder tests and inspections. r.. Ability to adjust knife-edges. M. Knowledge of the methods of receiving ranges and bat- tle orders aud communicating them to the sight setters and pointers. N. Ability to ring and adjust Morris-tube, dotter, and sub- caliber apparatus and to superintend the training at them. O. A practical understanding of the general terms used in ordnance and gunnery and the rules for conducting target practice, with a knowledge of the danger spaces at elementary and battle ranges. (6) Reports of examination will be in the following foi-m. No other report is required. These reports will be sent by the senior member of the board to the commanding officer of tiie ship to which the candidate belongs. The report will then be filed with the man's service record, unless there be a vacancy in the complement and he be given an acting appoint- ment as turret captain, first class, or chief turret captain to fill this vacancy, in which case it will be forwarded to the Bureau of Navigation, together with Form No. 1-B. Report of examination. Candidate's name Rate Attached to U. S. S. Date of examination , 191__. (Scale of marks: 5, excellent; 4, very good; 3, good; 2, fair; 1, indifferent; 0, bad.) Subject. Marks. Subject. Marks. Subject. Marks. A F K R G L P H M T) I N E J O 284 GUNNERY INSTEUCTIONS. We certify that we deem the candidate °°to*be''^ ^"^'J' qualified to talj:e charge of a turret at target practice or in action, in the absence of the turret officer, and *^°^°°* recom- mend him for acting appointment as chief^\urre\"captafn. '^^^^^' (Signatures of members of the board.) 509. Gun captains. — (1) By an Executive order dated July 25, 1903, enlisted men of the Navy, and extended to include Marines by Navy Department's Order No. 223 of September 27, 1912, who are regularly detailed by the commanding officer of a vessel as gun captains, except at secondary battery guns, shall receive, in addition to the pay of their respective ratings, $5 per month. In the case of men holding certificates of graduation from the gun-captain class of the petty officers' school, this $5 shall include the $2 per month to which such certificate entitles them. (2) No man shall be i-egularly detailed as gun captain in the above sense (that is, with extra pay) unless he has been examined and recommended by a board of three ordnance or division officers (exclusive of his own division officer, if prac- ticable) appointed by the commanding officer to determine his fitness for the position, but the above shall not be construed as preventing the detail of any desirable member of a guu crew as acting gun captain, though such detail shall carry with it no extra pay. Such details are necessary in order that, prior to their examination, candidates may have had actual experience in their duties in this capacity. (3) In order that he may draw his extra pay, a gun cap tain who has been recommended by a board, as above de- scribed, must be regularly detailed as captain of some in- dividual gun of the main battery. If, however, the arrange- GTTNNERY INSTRUCTIONS. S8fi inent of the ship's battery is such as to render necessary the detail of one gun captain to a group of guns, as for example, when a number of guns are more or less isolated and require a responsible person in charge, a man may be detailetl as gun captain of the group of guns, permitting an acting gun cap- tain to relieve him at his own gun. In no case will the num- ber of men on board who draw extra pay as gun captain exceed tlic number of guns of the main liattery on that vessel. (4) The following headings are given as covering the sub- jects on w-hich the candidates for appointment as gun cap- tains shall be examined (in the report of examinations these subjects will be referred to by letter only) : A. Ability to station and drill the gun crew. B. Thorough knowledge of the safety precautions to be ob- served in the service of the gun and of the method of pro- cedure in case of a failure to fire. C. Ability to bore sight the gun and adjust the telescope. D. Familiarity with the telescope sights of the gun, in- cluding their care, the precautions to be observed in their use. and their most probable derangements. E. Ability to shift and adjust the gas-check pad and breech mechanism. F. A practical understanding of the general terms used in ordnance and gunnery. G. A thorough familiarity with the mount, and ability to adjust such parts as require adjusting from time to time. H. A ready knowledge of how properly to direct the changes to be made in the range and lateral compensation in order to make hits again after shots have begun to fall off the target. I. A thorough knowledge of the firing circuit, with ability to detect and remedy local defects. .J. Knowledge of the metliod of receiving ranges and battle orders. 286 GUNNERY INSTRUCTIONS. K. Ability to rig and adjust Morris-tube, dotter, and sub- caliber apparatus, and superintend the training at them. (5) Reports of examination will be in the following form. No other report is required. These reports will be sent by the senior member of tlie board to the commanding officer of the ship to which the candidate belongs. The report will then be filed with the man's service record. Report of examination. Candidate's name, Rate, . Attached to U. S. S. Date of examination, 191- 'Scale of marks: 5, excellent; 4, very good; 3, good; 2, fair; 1, indiflerent; 0, bad.) Subject. Marks. Subject. Marks. Subject. Marks. A E I B F J C G K D H We certify that we deem the candidate ^^^ qualified for the duties of a gun captain. (Signature of members of the board.) INDEX. Article. Accuracy of fire^ 36 pointing 37 pointing necessary 64 torpedo fire 190 Adjustment of knife edges 306 (c) Afternoon work : 278 Air, density of. change of range due to 412 (3) Alignment of sights, necessity for correctness in_ 301 Ammunition 299 (d) crews, drill of 139 supply 138 supply, broadside guns 270 Angle fire, torpedoes, procedure for 185 Annoyances, avoidance of petty 20 Artificiality 143 of peace exercises, torpedo vessels, sub- marines 284 Assembling and disassembling torpedoes 180 Assembling men, difficulties of 280 Battle, diagram for spotters 371 Battle efficiency pennant 479 Battle inefficiency 481 Battle signal book 153 Batten, erecting -306 (b) Batten method of checking sights 306 Bells and buzzers fail 249 (I) Binoci:ar vision 350 Books on telephone, recommended . 336 287 288 INDEX. Article. BOEE, ELLIPTICITY OF . 461 BORESIGHT TELESCOPE 318 inverting of 319 BoRESiGHTiNG, definition 311 droop , 326 errors due to sights not being in hori- zontal plane with axis of boi-e 313 errors due to sights not being in ver- tical plane with axis of bore 314 method of 320 necessary 312 procedure after completion of 322 turret guns, procedure in 323 turret trainer's sight 316 uniform conditions necessary 315 BoEEsiGHTs, adjustment of 306 (g) preparation of 317 Breech mechanism, broadside guns 267 Broadside battery, general hints for officers of 260 material 262 organization and drill 261 Broadside gun, salvo fire 133 Broadside sights, checking of 303 Broken powder bag 249 (e) Broken rammer 249 (/) Bulletins, torpedoes 171 Burrs, removing 91 Buzzers and bells fail 249 [1) Cable, shell hoist, carries away 249 (j) Calibration and fire control, problems in 411-420 Cards for recording performance of gun pointers 274 Cartridge cases, primers, etc 450-452 Casualties ^ 28, 142 turret 249 INDEX. 289 Article. Cease firing 424 Censvke. reports uiifl coniniendation 17 Chambek capacity, variation in 460 Change of range, error in rate of 410 Charges, duiniuy i 94 reduced, spotting with 399 ( 'h.\u(;ei> toki'Kuoes,- prt'(;aulious 189 Checking sights after firing 325 Check telescope, advantage of 76 conducting drill witli 81 iiow mounted 79 with uiechaniciil target 77 types 78 <"hike kike-contkol officer 119 Circuit bijeakek opens 249 (k) Cleaning bill, turret 232 ("leanliness and smartness, necessitj' for 12 Clearing of vent 254 Coils, impedance, telephone 833 Collective gunfire, difficulties of 151 individual ship 109 several ships, training for 145-153 Commands, giving of 18 Comsiendation, censure, and reports 17 Competition 13 use of in training 2a Concentration 149. 150 (^'ondensers, telephone 334 Continuous aim 59 (&) Coordination, torpedo training ^ 169 r'REw, selection of, for broadside guns 271 suggestions from 9 Criticism of superiors 4 34776—18 19 290 INDEX. Article. Current observations, torpedo firing 198 Damage to torpedoes result of inexperience 167 Deck lugs, settling of 306 (i) Deflection corrections for observed mean error 412 (7) Deflection due to wind 303 initial, method of obtaining 302 initial, thumb rule for obtaining 304 tables 305 Density uk LoArnxo 450 variations in 432 Destkovei; actions 287 gun vu 286 Details, minor, importance of 21 imiiortance of 140 Deterioration of torpedo caused by salt water 205 Diagrams and signals, torpedo firing 204 Direct flight method of spotting 354 Directing, importance of correct torpedo 191 torpedo ■ 192 Dispersion 114 elements of . 428 mean, method of estimating 374 Distant ob.ject method of checking sights 305 Drv'isioN practice 152 Dotter. advantages of _ 09 delayed action 71 turret, installation of 220 variety of design 70 Double and single kakkeled. training necessary for tiring 132 Drift erkou 469 Drill at Drill gun 89 at spotting board and procedure 392,393 for range-finder party 342 INDEX. 291 Article. Drill gun, function of 87 gun, use of 88 requirements 248 shell 93 Drills, beginning 243 Drills, first 243 service conditions in 29 routine of, for broadside guns 272 Droop as affecting bore sighting 326 Dummy charges 94 Duties of turret officer, importance of 211 Elevating gear, turret 222 Elupticitv of bore of guns 461 Emery, use of 218 Energy, sources of for telephones 335 Erratic depth and deflection, torpedoes 183 flight of shell 464 Errors of gunfire 428-478 necessity for elimination of 41 Example, force of 3 Exit pupil of spotting glasses 348 Eyes, care of spotters' 353 Failure of plug to close 249 {