UNIVERSITY OF CALIFORNIA LOS ANGELES "pi- U 1e GIFT OF 5516021- Ordnance Department Document No. 2033 HANDBOOK OF ARTILLERY INCLUDING MOBILE, ANTIAIRCRAFT, MOTOR CARRIAGE, AND TRENCH MATERIEL PREPARED IN THE OFFICE OF THE CHIEF OF ORDNANCE WASHINGTON GOVERNMENT PRINTING OFFICE 1921 OKDNAXCE DEPARTMENT Document No. 2033 Office of the Chief of Ordnance Library ar WAR DEPARTMENT, WASHINGTON, July, 1921. The following publication, entitled " Handbook of Artillery, In- cluding Mobile, Antiaircraft, Motor Carriage, and Trench Ma- teriel," is published for the information and guidance of all students of the Ordnance training schools, and other similar educational organizations. The contents should not be republished without authority of the Chief of Ordnance, War Department, Wash- ington, D. C. BY ORDER OF THE SECRETARY OF WAR. JOHN J. PERSHING. General, Chief of /Staff. OFFICIAL : P. C. HARRIS, The Adjutant General. PREFACE. The data in this book are compiled for use in the Ordnance training schools and other educational organizations where a short, yet com- prehensive, survey of the existing calibers and types of guns and car- riages now in use by the United States Army is desired. With this in view, the descriptions and illustrations have been made as simple as possible, and technicalities have been reduced to a minimum so that the distinctive features of the various types of artillery materiel may be readily understood. This publication has been prepared in the mobile gun carriage sec- tion of the Artillery Division by Mr. Murray H. Resni Coff. The general discussion on the design and characteristics of mobile ar- tillery is intended for the instruction of student officers and enlisted specialists schools. The second edition of this book is to be distributed to various edu- cational institutions for a trial use in their classes, and the results of this trial should be productive of many constructive criticisms so that the next edition will more fully meet the varied needs of the schools and training units. The intention is to revise this book periodically, therefore suggestions and criticisms are cordially invited. Com- munications should be addressed to the Chief of Artillery Division, Office of the Chief of Ordnance, Washington, D. C. (4) LIST OF CONTENTS. Page. List of illustrations 7 Table of equivalents 14 History and development of artillery materiel 15 Artillery, classes of 26 Mobile artillery, types of 26 Cannons, their functions and construction, including breech mechanisms- 29 Mounts for mobile artillery 35 Recoil brakes and methods of counterrecoil 38 Aiming devices and sighting methods 40 Accompanying vehicles 53 37-millimeter gun materiel, model of 1916 57 2.95-inch Vickers-Maxim mountain gun materiel (with pack outfit) 63 75-millimeter gun materiel : Model of 1916 materiel 69 Model of 1916 MI materiel 83 Model of 1897 MI (French) materiel 87 Model of 1917 (British) materiel 103 Gun carriage limber, model of 1917 (British) 115 Gun carriage limber, model of 1918 119 Gun caisson, model of 1918 123 Gun caisson limber, model of 1918 125 3-inch gun materiel 127 Guns, models of 1902, 1904, and 1905, and carriage, model 1902 130 Gun limber, model of 1902 139 Gun caisson, model of 1902 ___ 141 Gun caisson, model of 1916 143 Gun limber, model of 1916 145 Battery wagon, model of 1902 147 Battery wagon, model of 1902 MI 148 Store wagon, model of 1902 149 Store wagon, model of 1902 MI 150 Forge limber, model of 1902 152 Store limber, model of 1902 155 Forge limber, model of 1902 MI 154 Store limber, model of 1902 MI 155 Battery and store wagon, model of 1917 156 Battery reel, model of 1917 159 Reel, model of 1909 MI__ 161 Cart, model of 1918 164 Wheels : 56-inch (steel tired) 167 57-inch by 3.5 inch (rubber tired) 167 Reel, model of 1917, for caissons 168 Automatic pole support 169 (5) 523505 Page. 105-millimeter howitzer materiel (German) 171 105-millimeter howitzer and carriage, model of 1898-1909 (German)- 173 105-millimeter howitzer caisson model 1898 (German) 178 105-millimeter howitzer carriage and caisson limber, model 1893 178 4.7-inch gun materiel 181 Gun and carriage, model of 1906 186 Gun carriage limber, model of 1905 195 Gun caisson, model of 1908 198 Gun limber, model of 1908 200 Gun caisson, model of 1916 202 Gun caisson, model of 1917 206 5-inch, 60-pounder gun materiel (British) 209 Gun, Mark I, and carriage, Mark II 213 Gun carriage limber, Mark II 216 Ammunition wagon, Mark II 219 Ammunition wagon limber, Mark II 223 155 howitzer materiel, model of 1917 (Schneider) 227 155 howitzer materiel, model of 1918 (Schneider) 231 Howitzer and carriage, model of 1918 236 Howitzer carr.'age limber, model of 1918 243 Howitzer caisson, model of 1918 245 155 gun materiel (Filloux) ,, 249 Gun and carriage, model of 1918 254 Gun carriage limber, model of 1918 263 6-inch gun materiel, model of 1917 (British) . .__ 265 7-inch naval tractor mount, Mark V 269 8-inch howitzer materiel (Vickers) 279 Howitzers, Marks VI and Vllli, and carriages, Marks VI and VII__ _ 288 Howitzer carriage limber, model of 1917 (Vickers) 299 Firing platform and wagon, model of 1917 (Vickers) 301 9.2-inch howitzer materiel (Vickers) 305 Howitzer and carriages, Marks I and II 310 Howitzer transport wagon 318 Howitzer carriage transport wagon 319 Howitzer platform transport wagon 321 240-millimeter howitzer materiel (Schneider) 323 Howitzer and carriage, model of 1918 329 Accessories 334 Transport wagons and limbers 339 Antiaircraft artillery 344 3-inch antiaircraft gun materiel, model of 1918 348 3-inch antiaircraft gun mount, model of 1917 363 75-millimeter antiaircraft truck mount, model of 1917 377 Gun and howitzer motor carriages 387 Self-propelled wheeled mount for 3-inch antiaircraft gun, model of 1917 390 Self-propelled caterpillar, Mark II, for 155 millimeter gun (Filloux), model of 1918 392 155 millimeter motor gun carriage (Christie), model of 1920 397 Trench warfare materiel 3-inch Stokes' trench mortar, Mark I 405 6-inch Stokes' trench mortar, Mark I 409 Prospectus 414 LIST OF ILLUSTRATIONS. Frontispiece. English archer using a long bow Balista and catapulta of the Greeks Sixteenth-century artillery 17 Italian Cerebotian of the fourteenth century 18 The " Mons Meg " of Edinburgh Castle 19 German breech-loading cannon of the sixteenth century 19 French artillery, 1800-1850 20 Soldier firing a mortar and bombshell requiring double ignition 21 German artillery, 1842-1874 22 Besieging a fortified castle, sixteenth century 23 Recoil brakes and methods of counterrecoil : Hydraulic brake (throttling bar) 39 Hydraulic brake (valve) 39 Hydraulic brake (central throttling) 40 Counterrecoil mechanism (spring, concentric columns) 41 Counterrecoil mechanism (spring, telescopic) 41 Hydro-spring recoil system 41 Hydro-pneumatic recoil system with floating piston 42 Hydro-pneumatic recoil system with fluid indirect compact with the air 42 Counterrecoil mechanism (hydro-pneumatic, central buffing) 43 Aiming devices : Elevating systems 47 Panoramic sight '. 48 Gunner's quadrant 49 Accompanying vehicles : Tractors hauling artillery 52 75 mm. gun carriage, mounted on trailer 54 37-millimeter gun materiel, model of 1916: Rear view of carriage in battery position 56 Carriage and ammunition cart, limbered 57 Left side view of tripod mount in battery position 59 Tripod mount in firing position 60 Gun disassembled on the march (wheels and axles left in the rear) 61 Gun and personnel on the march (ammunition cart left in the rear) 62 2.95-inch Vickers-Maxim mountain-gun materiel (with pack outfit) : Carriage in firing position : 64 Pack outfit on mule back 65 Rear view of carriage in battery 66 Detailed view of gun 67 Side view of carriage in battery 67 75-millimeter gun materiel, model of 1916 : Front view of carriage Right side elevation of carriage 70 (7) 8 T5-millimeter gun materiel, model of 1916 Continued. Page. Rear view of carriage . 71 Plan view of carriage 72 Left side view of carriage 7.; Breech mechanism 76 Gun at maximum elevation 77 Longitudinal section of recoil and counterrecoil mechanism 78 Elevating mechanism T'.i Traversing mechanism 80 Carriage and limber in traveling position .__ 81 75-millimeter gun materiel, model of 1916 MI : Left and right elevations ___ 82 Cradle assembly and longitudinal section 83 Left side view in firing position 84 Right side view in firing position 85 Arrangement of elevating mechanisms 86 75-millimeter materiel, model of 1897 MI (French) : Left rear view of carriage Front view of carriage 90 Longitudinal section of gun and carriage 92 Breech mechanism 93 Left side view of carriage 94 Right side elevation of carriage 95 Traversing and brake operating mechan sm 96 Abatage positions of carriage 98 Plan view of carriage 99 Sight, model of 1901 100 75-millimeter gun materiel, model of 1917 (British) : Left side elevation of carriage 102 Front view of carriage 103 Rear and front elevations of carriage 104 Rear view of carriage Hi." Breech mechanism 107 Recoil-controlling system 108 Elevating and range gear 111 Traversing gear 112 75-millimeter gun carriage limber, model of 1917 (British) : Front view of limber 115 Right side elevation of limber 116 Rear and front elevations 117 Rear view of limber 118 75-millimeter gun carriage limber, model of 1918 : Rear view of limber 120 Front view of limber 120 Assembled views of limber 121 75-millimeter gun caisson, model of 1918 : Assembled views of gun caisson 122 Front view of caisson 123 Gun caisson and gun caisson limber, limbered 124 75-millimeter gun caisson limber, model of 1918 : Front view of caisson limber 125 Assembled views of gun caisson limber 126 9 3-inch gun materiel, model of 1902 : Page. Front view of carriage 128 Rear view of carriage 128 Left side elevation of carriage 129 Gun, models of 1902, 1904, and 1905 131 Breech mechanism ; 132 Recoil-controlling mechanism 134 Carriage and limber, hauled by tractor 135 Carriage and limber in traveling position 135 Range quadrant 136 Rear sight 137 3-inch gun limber, model of 1902 : Rear view of limber 139 3-inch gun caisson, model of 1902 : Front view of caisson 141 3-inch gun caisson, model of 1916 : Front view, showing door swung upward exposing ammunition 143 Front and side elevations of caisson 144 3-inch gun caisson limber, model of 1916 : Side and rear elevations of caisson limber 146 Battery wagon, model of 1902 MI : Rear view of battery wagon 147 Store wagon, model of 1902 : Side view of store wagon 149 Side view showing store wagon and limber, limbered 151 Forge limber, model of 1902 MI : Top view showing interior of forge limber 152 Assembled views of forge limber 153 Store limber, model of 1902 MI : Top view showing interior of store limber 155 Battery and store wagon, model of 1917 : Rear right side view of battery and store wagon 156 Assembled views of battery and store wagon 157 Battery reel, model of 1917 : Left side view of battery reel 159 Reel, model of 1909 MI : Rear view of reel 161 Assembled views of reel 162 Front view of reel 163 Cart, model of 1918 : View showing reel and cart, 1'uibered 164 Rear view of cart 164 Assembled views of cart 165 56-inch wheel : Side view of wheel 167 Reel, model of 1917, for caissons : View showing reel mounted on caisson 168 Front and side elevations of reel 169 Automatic pole support : Sectional diagram of pole support 169 105-millimeter howitzer materiel, model of 1898-09 (German) : Left side view of carriage in battery position 170 View showing carriage limber and caisson coupled 172 Front view showing brakes and traveling lock 173 10 105-millimeter howitzer materiel, model of 1898-09 (German) Contd. Page. Longitudinal section of recoil mechanism 174 Equilibrator mechanism 176 Rear view of carriage 177 Front and rear view of carriage limber iT'.i Front and rear view of caisson 180 4.7-inch gun materiel, model of 1916 : View showing carriage and limber in traveling position 181 Left side view of carriage in battery 182 Assembled views of carriage equipped with tire brakes 183 Left front view of carriage equipped with band brakes 184 Assembled views of carriage equipped with band brakes 185 Front view of carriage equipped with tire brakes 186 Breech mechanism 186 Firing mechanism 187 Longitudinal section of gun and carriage 188 Front view of carriage equipped with band brakes 189 Rear right view of carriage 190 Elevating and traversing mechanisms 190 Range quadrant 191 Rear view of carriage equipped with tire brakes 192 Rear sight 193 Front view of carriage equipped with tire brakes 194 4.7-inch gun carriage limber, model of 1905 : Front view of limber l,- Assembled views of limber 196 4.7-inch gun caisson, model of 1908 : Right side view of caisson 198 4.7-inch gun limber, model of 1908: View showing gun caisson and limber, limbered 200 4.7-inch gun caisson, model of 1916 : Right front view showing chest doors open exposing diaphragms 202 Assembled views of gun caisson 203 Front view of gun caisson 204 4.7-inch gun caisson, model of 1917: Assembled views of gun caisson 207 5-inch (60-pounder) gun materiel (British) : Rear left view of carriage in battery 209 Carriage and limber in traveling position 210 View showing trail connected to limber 211 Rear right view of carriage 214 5-inch (60-pounder) gun carriage limber, Mark II (British) : Front view of carriage limber 216 Rear view of carriage limber 217 5-inch (60-pounder) ammunition wagon, Mark II (British) : Front view of ammunition wagon ' 219 Rear view of ammunition wagon Ammunition wagon and ammunition wagon limber, limbered 222 5-inch (60-pounder) ammunition wagon limber, Mark II (British) : Front view of ammunition wagon limber Rear view of ammunition wagon limber 155-millimeter howitzer materiel, model of 1917 (Schneider) : Right side view of carriage in traveling position Carriage in battery position (rear view) 228 11 155-millimeter howitzer materiel, model of 1917 (Schneider) Continued, .rage. Front view of carriage in battery position Side view of carriage en route 229 155-millimeter howitzer materiel, model of 1918 (Schneider) : Traveling position of carriage and limber 230 Assembled views of traveling position Detail view of howitzer 234 Breech mechanism 235 Firing mechanism 237 Recoil and counterrecoil mechanism 238 Longitudinal section of howitzer and carriage ' 240 Quadrant sight 241 155-millimeter howitzer carriage limber, model of 1918 (Schneider) : Plan and right side elevations 244 155-millimeter caisson, model of 1918 (Schneider) : Rear view of caisson 245 General assembled views 246 Front view of caisson 248 155-millimeter gun materiel, model of 1918 (Filloux) : Traveling position (right side) 249 Left-side view of carriage and limber in traveling position 250 Preparing carriage for battery position 251 Carriage in traveling position (rear view) 251 Longitudinal section of gun and carriage 252 Maximum elevation of gun 254 Breech mechanism 255 Breech mechanism and counterbalance cylinder 256 Carriage in firing position 257 Rear view of carriage in traveling position 258 Accessories and caterpillar wheel shoes 259 Elevating and traversing mechanism 260 Caterpillar adapters 261 155-millimeter gun carriage limber, model of 1918 (Filloux) : Front view of limber, showing caterpillar wheel shoes, mounted on wheels , 7 262 Front view of limber 263 Detailed view of limber 264 6-inch gun materiel, model of 1917 (British) : Plan view of carriage 266 Left-side elevation of carriage 267 7-inch naval tractor mount, Mark V : Carriage and limber in traveling position (front view) 269 Rear view of carriage 270 Left-side view of carriage in battery 271 Carriage and limber in traveling position (rear view) 273 Top carriage and axle details 274 Assembled view of hydraulic brake 275 View of axle mounted in track layer 276 Side elevation of track layer 277 Carriage in battery position, showing maximum elevation of gvm 278 8-inch howitzer materiel (Vickers) : Carriage in battery position (Mark VI) 279 Carriage and limber in traveling position (rear view) 280 Carriage in battery position (Mark VII) 282 Rear view of carriage, showing maximum elevation of howitzer 284 12 8-inch howitzer materiel (Vickers) Continued. Page. Right-side view of carriage in battery 285 Left-side elevation of Mark VI carriage 287 Rear right-side of carriage in firing position 288 Detailed view of howitzer (Mark VI) 289 Breech mechanism of Mark VI howitzer 290 Breech block 291 Firing mechanism 292 Front view of howitzer carriage 293 Elevating and traversing mechanism 294 Howitzer carriage mounted on firing platform 295 Sight assembled 296 Caterpillar adapters 298 8-inch howitzer carriage limber, firing platform and. wagon, model of 1917 (Vickers) : Limber in traveling position (front view) 300 Materiel 6n train and in battery 302 9.2-inch howitzer materiel (Vickers) : Carriage in battery position 304 Left side elevation of carriages assembled 306 Front view, showing maximum elevation of howitzer 307 Loading position, showing shell on tray 308 Longitudinal section of carriage 309 Rear view of carriage, showing howitzer at miximum elevation 310 Breech mechanism (Mark I) 311 Breech mechanism (Mark II) 312 Gear regulating recoil 313 Method of loading, showing loading gear mechanism in action 314 Right-side view of carriage in battery 314 Traversing gear 315 Sight assembled 316 9.2-inch howitzer transport wagon (Vickers) : Method of mounting howitzer 318 Materiel 6n train 320 240-millimeter materiel, model of 1918 (Schneider) : Materiel n train __. 322 Front view of carriage, showing maximum elevation of howitzer 323 Carriage in loading position 324 Method of loading the howitzer with rammer car 326 Left elevation of carriage with howitzer at maximum elevation 327 Breech mechanism 328 Mounting the cradle 330 Recoil and recuperator mechanism 331 Elevating and quick-loading gear mechanism 332 Mouting the top carriage 333 Method of lowering platform . 334 Sight assembled ^ 335 Erecting frame in position 330 Left side view of carriage 338 240-millimeter howitzer transport limbers and wagons : Howitzer transport wagon 339 Cradle transport wagon 339 Mounting the howitzer 340 Top carriage transport wagon ; 341 Platform transport wagon 341 13 Antiaircraft artillery : Page. Antiaircraft artillery in action 345 3-inch antiaircraft gun materiel, model of 1918 : Carriage in traveling position 347 Carriage in battery position (front view) 349 View showing outriggers folded 350 Longitudinal section of carriage 351 Breech mechanism 352 View showing right rear outrigger with jack spade and float removed- 354 Side view of carriage in battery position 355 Assembled view showing carriage in firing position 357 Front view of trailer 358 Sight on left side of carriage 359 Sight on right side of carriage 360 3-inch antiaircraft gun mount, model of 1917 : Longitudinal section of gun mount 362 View showing mount in action 363 Right side elevation of gun mount 364 View showing right side of mount 365 Breech mechanism 367 Vertical section showing breech open 368 Elevating and traversing mechanisms 371 Left side elevation of gun mount 372 75-millimeter antiaircraft truck mount, model of 1917 : Plan view of truck mount 376 Truck in traveling position (right side view) 377 Sectional elevation of gun mount 378 View showing truck mount in action 379 Gun mount showing gun at maximum elevation _ 382 Truck in traveling position (left side view) 383 Firing and stability jacks 385 Truck mount in battery position. 386 Gun and howitzer motor carriages : 105-millimeter howitzer motor carriage, model of 1920 387 3-inch antiaircraft wheeled mount showing gun at maximum eleva- tion ' ; 388 Self-propelled wheeled mount for 3-inch antiaircraft gun, model of 1917 : Left side view of mount in traveling position 390 Self-propelled caterpillar Mark II, for 155-millimeter gun (Filloux), model of 1918 : Plan view 392 Traveling position, front view 394 Traveling position, rear view 395 155-millimeter motor gun carriage (Christie), model of 1920: Side elevation of mount in traveling position 397 Rear view of mount in battery position 399 Trench warfare materiel : Trench warfare 402 Arrangement of trenches 403 3-inch Stokes's trench mortar, Mark I : Mortar in action 405 Front view of trench mortar 406 Rear view of trench mortar__ 407 6-inch trench mortar, Mark I : Methods of installation of trench mortar 410 Left side view of mortar 411 Method of loading trench mortar 412 Rear view of mortar__ 413 TABLE OF EQUIVALENTS. 1 mil 3.37 minutes. 1 degree 17. 777 mils. 1 meter (m) 39.37 inches. 1 centimeter (cm) 0.3937 inch. 1 millimeter (mm) 0.03937 inch. 1 kilogram (kg) 2.2046 pounds. 1 dekagram (dk) 0.3527 ounce. 1 gram 15.432 grains. 1 liter 1.05671 quarts (U. S.). 1 quart (U. S.) 0.9463 liter. 1 inch 2.54 centimeters. 1 foot 0.3048 meter. 1 yard 0.9144 meter. 1 square inch 6.452 square centimeters. 1 kilogram (kg) per square centimeter 14.223 pounds per square inch. 1 cubic inch 16.39 cubic centimeters. 1 cubic foot 0.02832 cubic meter. 1 cubic yard 0.7645 cubic meter. 1 ounce 28.35 grams. 1 pound 0.4536 kilogram. (14) HISTORY AND DEVELOPiMENT OF ARTILLERY MATERIEL. In taking up the study of artillery, the student should know something of its history, the development of guns and gun carriages, and the reasons for the various changes in ordnance materiel which have taken place from time to time. History shows that artillery development has gone steadily forward. Every military power has striven with the aid of its best engineers, designers, and manufac- turers to produce a stronger weapon, either with or without a heavier projectile, but in every case striving for greater power. The sole use of a gun is to throw a projectile. The earliest pro- jectile was a stone thrown by the hand and arm of man either in an attack upon an enemy or upon a beast that was being hunted for food. In ancient times the man who could throw the heaviest stone the longest distance was the most powerfully armed. During the Biblical battle between David and Goliath, the arm of David was strengthened by a leather sling of a very simple construction. Much practice had given the youthful shepherd muscular strength and direction, and his stronger arm and straighter aim gave him power to overcome his more heavily armed adversary. From the earliest times man has felt the want of arms that would kill at a distance, and the ingenuity of the talented has successively been taxed to produce such weapons. The effect of a stone or spear thrown by hand so often proved insufficient that at once a desire arose to assist the muscles by the aid of some mechanical force. The sling was probably the first weapon used for hurling missiles. Its invention is attributed to the Phoenicians or the inhabitants of the Balearic Isles, who were extremely expert in its manipulation. The sling was used for many centuries as a military weapon, and its last appearance was in the Huguenot War of 1572. The bow was probably invented about the same time as the sling, and for many centuries was considered the most effective offensive weapon in warfare. Great skill was attained by the ancients in its use, and many accounts are to be found relative to the extraordinary force and precision with which an arrow might be projected. The long bow has always been the more universal weapons, the cross- bow being a comparatively modern invention, and its use con- fined almost entirely to Europe. The crossbow was extensively used for sporting as well as military purposes, and it must have been 5516021 2 (15) 16 a crossbow that William Tell employed in his notable feat. The Genoese and Gascons were the most famous crossbow men in the armies of Europe. The crossbow of the fourteenth and fifteenth centuries were sometimes made with sights affixed to them. Some specimens possessed a back sight having three or more peepholes, one over the other, which were evi- dently intended as guides for elevation. Projectile-throwing ma- chines were developed after the fashion of a crossbow mounted upon a small wooden carriage which usually was a hollowed trough open on top and upon which a stone was laid. The thong of the crossbow was drawn by a powerful screw operated by man power, and the cross- bow- arrangement when released would throw a heavy stone quite a distance. This was an attempt by mechanical means to strengthen the stroke of the arm and increase the weight of the projectile. The Bible states that King Usia (809-757 B. C.) placed types of artillery on the walls of Jerusa- lem. The Romans used it in the Punic Wars. The Alexandrian tech- nicians established sci- entific rules for the con- struction of early weap- ons. Athenacus reports Catapults having a range of 656 meters and that the gigantic siege tower at Rhodes successfully resisted stone projectiles weighing 176 pounds. The first use of guns or cannon as a medium for hurling projectiles by means of gunpowder is buried in obscurity ; we have knowledge ENGLISH ARCHER USING A LONG BOW. BALISTA AND CATAPULTA OF THE GREEKS. 17 of Chinese using a form of gunpowder; not, however, for military parposes, but for pyrotechnics, at a period long before the Caucasians. It is possible to trace back the invention of gunpowder to many centuries prior to the Christian era. Most writers upon this subject seem agreed that it was known to the Chinese and Indians, but the descriptions given are so vague that it is difficult to make the various accounts coincide. The earliest mention we have of gun- powder is in the Gentoo Laws, where it is mentioned as applied to firearms. This particular code is believed to have been coeval with the time of Moses. Gunpowder has been known in India and China far beyond all periods of investigation. There are many ancient Indian and Chinese words signifying weapons of fire, "heaven's thunder," "devouring fire," "ball containing terrestrial fire," and such ex- pressions. The ancient Indians made great use of explosives, including gunpowder, in pyrotechnical displays. The introduction of powder into Europe took place early in the Christian era; some believe it was brought by the Moors into Spain and others that it came through the Greeks at Constantino- ple. Both may be correct, but it is certain that pow- der or a substance closely akin to it, was used at the siege of Constantinople in A. D. 668. The Arabs, or Saracens, are said to have used it in A. D. 690 at the siege of Mecca. The earliest mention of guns we have is that Seville was de- iVided in 1247 by cannon throwing stones; Mibela in Spain, when lie.-eiged in 1259, was also defended by a machine resembling cannon; in 1273 Abou Yousof made use of cannon throwing stone balls at the siege of Sidgilmessa ; in 1308 Ferdinand IV of Castile, at the sit -f Granada against Alicante, in 1339 at the siege of Puy-Giull ort J, i,<\ in the same year a* the siege of Cambray by Edward II! n 1 '3*0 by Lequesnoy before Mirepoix, in 1345 before Monsegur, and in 1346 at Crecy; we have) many instances of cannon being used in the second half of the four- teenth century. About 1350 the North German knights had iron guns, and a little later the Free Hanse Towns armed themselves in the same way. In the year 1356 appear large amounts in the ITALIAN CERBOTIAN OF THE FOURTEENTH CENTURY, MOUNTED ON SEMI- PORTABLE CARRIAGE. accounts of the town of Nuremberg as having been spent in pur- chasing cannon and guns; and in 1365 Duke Albert of Branden- . -erg defended Einbeck very effectually " with fire boxes." The first records show that the Huns used artillery at the seige of v/ividale, Italy, in 1331. The material was, of course, very crude, and its effectiveness at that time depended largely upon the smoke and noise produced. The barrels, or cannons, in those days were constructed of wood, wrapped with wire or iron bands, and the projectiles were of stone. These guns were not mobile guns in any sense ; they were transported with the utmost difficulty, and were subject to capture by sudden raids of the enemy. The British were the first to actually bring guns out into field warfare. They appeared at the Battle of Crecy in 1346, much to the dismay of the enemy. They shot anything that would go into the barrels of the guns, even bundles of arrows. The ordnance 19 THE " MONS MEG " OF EDINBURGH CASTLE. (Weighing near 4 tons, and shooting a stone bullet weighing 350 pounds.) department of Edward III consisted of 340 men, with but 12 artil- lerymen, showing that at that time not much attention was paid to what is now an indispensable arm of the service. In 1415 the num- bers had increased to 25 " master gunners " and 50 " servitour gun- ners." The gunner was the gun captain and had general charge stores. In action he laid the piece and did the actual firing. The early can- non of Europe were known by various names in the different coun- tries. In Italy they were known as bombardes, probably derived from " a bombo et ardore " on account of the great noise which the firing of them occasioned. The French called them " quenon " or " cannon," the Germans " buchsen " or " boxes." and the Netherlander " vogheleer " or " veugliares." Besides these terms there were many others applied to the various models, but it was not until the beginning of the fifteenth century that cannon were classified and named according to their size. Cannon were not adopted or manufac- tured in France until 1338, and even for many years after- wards the French looked upon those nations who used them as barbarians. The early cannon GERMAN BREECH LOADING CANNON OF THE SIX- W 6 T 6 made of TEENTH CENTURY. WTOUght, not Cast metal, the first account we haye of cast cannon being in 1378. when a founder named Aran, at Augsberg, in Germany, cast 30 of a metal composed of copper and tin. In 1413 Mahomed II, at the siege of Constantinople, had an enormous cast cannon. The bore is said to have been 48 inches in diameter and the stone bullet to have weighed 600 pounds. 20 21 The greatest example of artillery in the fifteenth century was at the siege of Constantinople by the Turks in 1453. They used a type of mortar that hurled huge stones, some weighing TOO pounds. Some of these guns survived to engage the British in 1807. The majority of artillery at that date was for siege work. In the Italian wars waged by Charles VIII of France artillery played a conspicuous part. However they lacked the necessary mobility and consequently were captured and recaptured several times in a single engagement. At that, artillery had done some excellent work before small arms had attained any prominence. Although field artillery was introduced in the Hussite Wars. 1410 to 1424, it was not until the Thirty Years' War that they really dis- played a mobile nature. The French had invented the limber, and the connection between it and the gun trail was made with a rope. The first gun that was moved by horsepower was mounted on an oblong frame, the gun- ner sitting directly be- hind the piece. The forepart of the oblong was mounted on two wheels and the rear end was supported by the horse which was inside of the oblong frame. The majority of the guns were 4- pounders. for as yet no way had been, devised for 'the proper trans- portation of the heavier guns. The ancient carriages were remarkable because of the fact that in general design they embodied the same principles which are included in the field carriages of to-day. One example from the fifteenth century shows a breech-loading gun mounted in a cradle supported by trunnions on the forward extension of the trail over the axle. The cradle was elevated by a pin-and-arc arrangement, sup- ported on the trail. The axle, supported by wheels, passes through the trail to the rear of and below the cradle trunnion support and in front of the point of attachment of the elevating arc. Field guns fell into disuse about 1525 with the introduction of musketry, and remained so until 1631, when Gustavus Adolphus gave artillery its true position on the battle field. SOLDIER FIRING A MORTAR AND BOMBSHELL REQUIRING DOUBLE IGNITION. 22 23 Swedish artillery reigned supreme in the early part of the seven- teenth century. Gustavus introduced marked changes by making the guns and the carriages lighter and handier his motto was mobility and rapidity of fire. About the middle of the eighteenth century, guns were either 24. 12, 6, or 3 pounders; the units were divided into brigades of 4, 5, and 6 guns, respectively, and began to be separated into heavy and light units. Each field gun was drawn by four horses with a can- noneer on each of the lead horses. The ammunition carried was 100 rounds of solid shot. BESIEGING A FORTIFIED CASTLE, SIXTEENTH CENTURY. Artillery was not of any great use in the field until along in the eighteenth century, at which time guns were lightened, particularly so in France ; powder was gradually compounded on better recipes, gun metal was improved, paper and linen cartridges were intro- duced, gun carriages were provided with an aiming wedge, and many new styles of guns and mortars, and for which ammunition was invented. Science lent its aid to practical men and not only exhausted chemical ingenuity in preparing powder and metal, but mathe- matical formulae were evolved for the artilleryman, and the value of ricochet firing was discovered. The howitzer necessary for high angle fire put in its appearance in 1785, being introduced by the French Army. Horse artillery appeared in the French Army in 1791. In 1800 the horses were paired off, with a driver on each near horse, as is done to-day. In 1808, at Vimera, the first case shot came into use, its invention being credited to an English colonel by the name of Shrapnel. It later 24 became known as shrapnel. The type of case shot used by Napoleon had a fuze that could be used for two different ranges. Napoleon also introduced the idea of massing artillery along a long front. Field artillery next began to appear in the form in which it was to retain, with but a few changes, until the era of the modern field carriage. The cradle disappeared, muzzle-loading guns cast with trunnions taking its place, and a stepped wedge resting on the trail superseded the pin and arc. With the exception of the gun, most parts of these carriages were of wood, and remained so until 1870, when metal carriages came into general use. Muzzle loading guns had supplanted breech-loaders because of the poor obturation and the many accidents resulting from use of the latter type. Although numerous experiments were made, breech-loading guns did not come into vogue again until 1850, when the experiments of Maj. Cavalli (1845), the Walnendorff gun (1846), and the Arm- strong gun (1845) produced satisfactory types. Between 1860 and 1870 rifling appeared. This caused sighting to -be given greater consideration, as a rifled gun shoots very accurately. During our Civil War the smoothbore was generally used, although rifled guns had made their appearance toward the close of the con- flict. Direct laying was the only method of fire employed at this time. The period from 1880 to the present has brought about changes in gun construction which possibly have been equaled in impor- tance to artillery only by the present change which is taking place due to the development of motor transportation and self-propel- ling motor carriages. In this period, in rapid succession, came the modern breech block, and with it the rapid-firing gun. This called for a recoil mechanism system to break the force of recoil of the gun and restore it to its firing position without seriously disturbing the lay of the piece. The possibilities of rapid and more accurate fire were perfected. In 1886 came the invention and use of smokeless powder. Previous to this time the great amount of smoke produced by the black powder when the piece was fired retarded the rapidity of fire, because it enveloped the materiel in a cloud of smoke which obscured the target and made it impossible to fire again until the smoke had blown away. The advent of smokeless powder also made possible the selection of concealed positions. This in turn made indirect fire feasible and necessitated the development of better sights. Indirect fire gave to the commanders of firing units a greater control over their fire. With the use of modern recoil mechanisms, the cannoneers were permitted to serve the piece continuously, a condition which was impossible with 25 the recoiling carriage. Shields were next introduced on guns to protect the personnel and make it more difficult to put the piece out of commission. The recent great struggle in Europe has brought about conditions and problems which, heretofore, have never existed in warfare. To meet these, sweeping changes have been made in almost every arm of the service, but probably the greatest and most radical change has been the motorization of the artillery. Heretofore, successful advances by the troops were limited to'com- paratively short distances, due to the impossibility of advancing artillery, ammunition, and supplies over ground which is often muddy, full of shell holes, and otherwise difficult to travel over with enough rapidity to keep up with the advancing infantry troops. The problem of transporting army equipment in the field led to the introduction of tractors and motor trucks. The development of the caterpillar tractor for hauling field artil- lery, which is able to maneuver over almost any kind of terrain on the battle field, led to the question of the possibility of mounting guns directly on a self-propelled vehicle equipped with caterpillar treads. Early in 1918 an 8-inch howitzer was mounted on a self- propelled carriage and was fired at angles of elevation varying from i> to 45 with very satisfactory results. This experimental cater- pillar was tested, and it was found to be practical, easy to maneuver, and able to withstand the firing strain of the howitzer. As a result of this test, several types of experimental self-propelled motor car- riages have been manufactured, with armaments varying from 7-V millimeter guns to 240-millimeter howitzers. ARTILLERY. Artillery has come to mean all firearms not carried or used by hand. excepting machine guns. Artillery is divided into two general classi- fications : Artillery of position and mobile artillery. Artillery of position is that which is permanently mounted in fortifications. Mobile artillery consists of two classes: First, the artillery de- signed to accompany an arm in the field; second, railway artillery, which requires tracks for its transportation. The first type only is discussed in this book. MOBILE ARTILLERY. In designing any gun intended for use in the field, there are two important requirements power and mobility. Granting that a gen- eral type of gun has been decided upon, it is evident that any in- crease in either of these two factors is at the expense of the other. It is necessary to balance the two, keeping in mind the specific pur- pose of the gun under consideration. We thus find it necessary to have several distinct classes of guns, ranging from the very power- ful and almost immobile, to the very mobile and comparatively weak. The general classification is : Heavy field, light field, mountain guns or pack howitzers, trench mortars, and infantry accompanying guns and howitzers. Besides the classification, based upon power, there is another, based upon the shape of the trajectory. For the attack of targets that can be reached by it, flat trajectory fire is preferred on account of its power and accuracy. Cases frequently arise, however, where such fire is useless, either the gun or its target being so concealed and sheltered by intrenchments or the nature of the terrain that higher angles of departure and fall become necessary. To provide for both cases, there are two or three types of weapon the long gun for flat trajectory, the shorter howitzer for curved trajectory, and sometimes the still shorter mortar for high-angle fire. We thus subdivide our original classes and distinguish, for example, the light field howitzer, the heavy field gun, etc. Evi- dently the number of separate calibers that might be adopted to make up a complete series of types is very large. But it is important to reduce this number to a minimum, both from considerations of economy and also to avoid complication in ammunition supplies. (26) 27 Guns were ordinarily intended for attacking targets that could be reached by direct fire; that is, by fire at angles of elevation not exceeding about 15. For the attack of targets that are protected against direct fire and for use in positions that are so sheltered that direct fire can not be utilized, curved fire that is, fire at elevations exceeding 15 is necessary. The howitzer, a short gun designed to fire at comparatively large angles of elevation, is therefore pro- vided. Field guns are now designed which permit fire at elevations as high as or higher than is permitted by the howitzers. This is partic- ularly true of antiaircraft guns and those designed for use against entrenched positions. This development is an improvement in the effectiveness of the field gun, but it will not eliminate the use of howitzers of equal mobility, as the latter use projectiles of much greater weight than those of gun materiel of the same caliber. The original American plan of field artillery design provided for each caliber of gun, a howitzer of equal degree of mobility. In fur- therance of this idea and to reduce to a minimum the number of calibers of mobile artillery, and thus simplify as far as possible the supply of ammunition, the calibers of the guns and howitzers were so selected that, while both guns and howitzers fulfilled the require- ments as to weight and power for each degree of mobility, the caliber of each was the same as that of the gun of the next lower degree of mobility. That is, the howitzer corresponding in mobility to one of the guns is of the same caliber as the next heaviest gun. The recent developments in American artillery, as well as the introduction of artillery of foreign design into the American service, have sustained this principle. Under ordinary conditions the 3-inch field gun with its weight of about 3.900 pounds behind a six-horse team, is about as powerful a gun as can follow an army in motion. For this reason, a gun of ap- proximately this caliber has been adopted by most nations as the principal field gun. The artillery of all military powers now comprises what are known as " rapid-fire " or " quick-firing " guns. This designation is too firmly established to be changed, although it can not be considered as accu- rately descriptive since rapidity of fire is characteristic of nearly all modern types. The real distinguishing mark of a rapid-fire gun is that its carriage does not move materially in firing ; instead, the gun recoils on the carriage and is returned to the firing position by springs or their equivalent. There are a number of other features, some of which are found in all rapid-fire models; but these are of secondary significance and either old ideas which could not be worked out practically before the development of the gun-recoil carriage or else improvements developed since in the effort to get the best results out 28 of it. For example, it is useless to attach shields to a rigid carriage, for, since the cannoneers have to stand clear to avoid the recoil, they can not take advantage of them. Mechanism for traversing the piece on its carriage is unnecessary with the rigid system, but be- comes necessary as soon as we adopt a carriage that remains more or less firmly anchored to the ground. Fixed ammunition and instru- ments for indirect laying are not essentially a part of either a rigid or a gun-recoil system: they are sometimes used with the former and occasionally, but rarely, omitted from the latter ; but they have their full value only in rapid-fire material. Our mobile artillery is divided into the following classes: (a) Divisional artillery; such as, the 3-inch and 75-millimeter guns and 105-millimeter howitzers. (The 155-millimeter howit/i-r to be used as a substitute.) (?>) Corps artillery; such as, the 4.7-inch guns and 155-millimeter howitzers. (c) Army artillery; such as. the 155-millimeter guns, 8-inch and 240-millimeter howitzers. Any caliber may, if required, be assigned to army artillery. (d) Mountain or pack materiel transported on the backs of mules. For mountain service the system composed of gun and carriage must be capable of rapid dismantling into parts, none of which forms too heavy a load for a pack mule. The weight of the load including the saddle and equipment should not exceed 350 pounds. The mountain gun in our service is the 2.95-inch. (e) Infantry accompanying guns; such as, the 37-millimeter. (/) Trench mortars. Carriages are designed to function in a certain way and are not temperamental. They follow absolutely and certainly fixed mechan- ical laws. If they fail rtere is always a reason which can be remedied. Certain parts are jgiven certain shapes and forms, and are machined to fine adjustments;\herefore in taking down and assem- bling artillery materiel brains *id dexterity are the tools to use rather than force and sledge hammers. Treat these guns as you would a friend whom you know you can depend on. They will not fail you. CANNONS. THEIR FUNCTIONS AND CONSTRUCTION. "A cannon is a machine by which the force of expanding gas is used for the purpose of propelling a projectile in a definite direction.'* A cannon consists of a metal tube, closed at one end, and of suffi- cient strength to resist the pressure of the gases of explosion. The force of the expanding gases acting on the base of a projectile placed in the cannon causes it to start on its flight. When the charge is ignited, the explosion or rapid combustion of the powder gives rise to a large amount of gas, which tends to expand and to occupy a space greater than that in which the powder was originally con- tained; consequently, it exerts a pressure in all directions, and the energy developed is utilized in forcing the projectile from the tube. The major portion of the energy is distributed as follows : (a) Energy of translation of the projectile. (ft) Energy of rotation of the projectile. (c) Energy of translation, in recoil, of the gun. (d) Energy of translation of the unburnt charge and gases. (e) Energy consumed in overcoming the passive resistance of the projectile. This resistance arises from the friction of the projectile against the walls of the bore, and of the rotating band against the driving edges of the lands. In the first stages, it also arises from the cutting of grooves in the rotating band by the lands. The balance of the energy is expended by being lost as heat to the gun and that which remains in the gas as sensible or latent heat. In the cannon, the space in which the powder is burning has a fixed capacity until sufficient force has been developed to start the projectile. When the projectile begins to move, the capacity of the gas container begins to increase, and this increase tends to decrease the expansive force of the gas. Thus the progressive explosion of the powder, by increasing the amount of gas in the container, is increasing the expansive force, while at the same time the increase in the size of the container is decreasing the expansive force. If the effects of these two opposing factors could be maintained equal in value from the time the projectile starts to move until it leaves the muzzle of the cannon, it would then be possible so to regulate the powder charge that the force developed would rise to the maximum pressure safe for the cannon when the projectile starts to move, and would then remain constant until the projectile leaves the muzzle. This would be the ideal progressive explosion, for since the maximum (29) 30 allowable pressure would be exerted upon the projectile during its entire path while in the bore, the maximum possible initial velocity for the projectile and cannon considered would be developed. A cannon may be considered as a tube destined to withstand a given pressure from within, throwing a projectile which shall pro- duce certain effects at given distances. In constructing such a tube we must first consider what pressures it will have to withstand at the various points of its length, and then make it strong enough to insure perfect safety. Not only must the gun be sufficiently strong, but it must not be too heavy; so it is important that the material shall be arranged in such a manner that there may be no waste of its strength in fact, so arranged that every part shall perform its own share in withstanding the pressure from within. Shortly after the shot begins to move the pressure inside the gun decreases, and continues to decrease as the projectile approaches the muzzle; for this reason the piece is made stronger at the powder chamber than toward the muzzle end. Looking simply to the construction of a gun cylinder, we find that the two principal stresses to which such a cylinder is subjected upon the explosion of a charge are, first, a circumferential or tangential stress or tension, coupled with a radial stress, tending to split the gun open longitudinally; second, a longitudinal stress tending to pull the gun apart in the direction of its length. It may be readily understood that during the travel of the pro- jectile through the bore of the gun, from the instant of ignition of the charge until it has left the muzzle, tremendous stresses are set up in the tube. In the earlier days of ordnance construction these stresses were met by sheer weight of metal, but as the weight of projectiles increased, with consequent increase in powder charges, this weight of metal became so great as to impede the desired mo- bility of the material. Consequently forgings of refined and alloyed steels took the place of the castings or forgings of iron or simple steels. As explosives increased in power the plain tube, even though built of alloyed steels, became incapable of containing the chamber pres- sures, even though of excessive weight. This problem was finally met through the construction of built-up and wire- wrapped guns. A built-up gun is one in which the principal parts are separately constructed and then united in a peculiar manner; and guns so con- structed may be composed of different kinds of metal or of the same kind of metal throughout. On the wire-wound gun the wire is wound in layers around an inner tube of steel. Each layer is wound with a tension on the wire, and each exerts a compression on the layer which is beneath it. 31 The result is that when completed the outer layers are in extension, gradually diminishing to the inner layers, which are in compression, all within the elastic limit. RIFLING consists of a number of helical grooves cut in the sur- face of the bore. The soft metal of the rotating band of the projec- tile is forced into these grooves and causes the projectile to take up the motion of rotation as it passes through the bore. Rotation of the projectile around its longer axis is necessary for stability in flight. By twist of rifling is meant the inclination of one of the grooves to the element of the bore at any point. Rifling is of two kinds : (a) Uniform twist, or that in which the twist is constant through- out the bore. (>) Increasing twist, or that in which the twist increases from the breech toward the muzzle end of the bore. The object of rifling is to impart to the shell a rapid rotation about its axis and thus give it the powers of a gyroscope. These powers resist any deflection of the shell's longitudinal axis. If it were not thus given gyroscopic properties, with great power to resist deflecting influences, inaccuracies would result. Rotation is obtained by rifling in the bore of the gun and a soft metal (copper) rotating band on the body of the shell. This band is forced into the grooves as soon as the shell starts from the origin of rifling. The rotating band follows the grooves, and as these are spiral, the shell is rotated as it travels the bore. The grooves of rifling are spirals. The pitch of the rifling, or the inclination of grooves to axis of bore, is called twist. It is usually designated by one turn in so many calibers. With uniform twist the projectile must take its rotation the instant it starts, whereas with increasing twist the rotation may be impaired gradually. With increasing twist there appears the disadvantage that on account of the constantly changing angle it is hard to preserve gas tightness be- tween the rotating band and the grooves. A rifled cannon is so called on account of the spiral grooves which are cut into the surface of the bore, and into which the soft metal of the rotating band on the projectile is forced, thus imparting to the projectile a motion of rotation. The spaces between grooves are called lands. The caliber of a gun is the diameter across the tops of the opposite lands. The bore is the cylindrical hole in the gun extending from breech face to muzzle face of the tube. That part of the bore from the breech plug, when closed, to the point where rifling begins is called the powder chamber. Its capacity is the total cubical contents from plug face to base of projectile, when the latter is " seated " in 5516021 3 32 position for firing. The rear part of the chamber is cylindrical for some distance. This cylinder merges into "the slope of the powder chamber," an easy slope, which in turn merges into the " com- pression slope," which ends in the "seat of rifling"; that is, the rear end of the rifled cylinder. When a shell is in position for firing, its rotating band takes the seat of rifling. Initial velocity. By initial or muzzle velocity is meant the rate of travel in feet per second at which a projectile leaves the muzzle of a cannon. In its application to practical problems, however, we usually take as the initial velocity the maximum velocity attained by the projectile. This is acquired, not strictly at the muzzle, but a short distance beyond it ; for so long as the projectile is in the powder blast the force of the expanding gases continues to a limited extent to act upon it, and so long as this force is greater than the retarding force of the air, the velocity of the projectile is increased. Density of loading. The density of loading is the ratio of the weight of the powder charge to the weight of a volume .of distilled water, at the temperature of maximum density, that will fill the powder chamber. This ratio expresses the weight of powder per unit volume of the powder chamber, in terms of the weight of a unit volume of water. The force developed by the explosion of powder in a container de- pends both upon the amount of powder and upon the size of the container; that is, it depends upon the amount of powder per unit volume of the container, or in other words upon the density of load- ing. The density of loading, therefore, has a direct and important bearing upon the initial velocity, and in order that it may be deter- minable and constant in practice under any given set of conditions, it is important to keep constant the size of the container. It is con- sequently essential that projectiles always be well seated, so that in any particular piece, the base will always be the same distance from the face of the breech. Ignition, inflammation and combustion. By ignition is meant setting fire to the charge ; by inflammation, the spread of flame over the surface of each grain and from grain to grain of the charge; and by combustion, the burning of the inflammed grain from the surface of ignition inward, or outward, or both, according to the form of the grain. It is desirable to produce as nearly as possible a simultaneous ignition of all the powder grains of the charge, in order that inflammation and combustion be as nearly uniform as possible, thus eliminating variations in the rate of emission of gas and consequent differences in force developed at any elapsed time a"ter the first particle of a charge has been ignited. For this reason, in the larger charges an igniting charge of black powder is attached to each end of each section of a powder charge, and a core of black 33 powder is extended from end to end as well. In the smaller charges, the igniting charge is attached to one end only of the propelling charge, and the core is omitted. Size and shape of the powder grain. The force or pressure de- veloped at any instant of an explosion depends upon the amount of gas that has been evolved. This depends upon the rate of combus- tion, and the area of the burning surface. Therefore the size and shape of the grain have an important bearing upon the initial velocity. As a rule, the larger the grain the less will be the area of burning surface per pound of powder, and the slower will be the rate of emission of gas for the same rate of burning for any given charge. The rate of production of gas at any instant depends upon the area of the burning surface at that instant, which, in turn depends not only upon the size but also upon the shape of the grain. Any change in this area as combustion progresses produces a corresponding change in the rate. In a nonperf orated grain of any shape, as the outer layers are consumed, the area of burning surface decreases, thus tending to decrease the rate of gas production. This decrease, com- bined with the increase in size of container after the projectile starts to move, will cause the pressure to start decreasing after having reached a maximum, thus allowing the initial velocity to fall below that which would be attained could the pressure be maintained at its maximum. Hence, to keep .the burning surface from decreasing, perforated grains are employed, which are consumed by combustion progressing outward from the inner surfaces of the perforations, as well as inward from the exterior surfaces of the grain. Thus while the exterior burning surfaces are decreasing as combustion progresses, the surfaces of the perforations are increasing, and the total burning surface is maintained nearly constant. In this way the maximum explosive effect is more nearly approached. A BREECH MECHANISM, or fermeture, is a mechanical device for closing the rear end of the chamber or bore of a breech-loading gun. The term includes the breechblock or plug, all mechanism contained in or with it, and the necessary operating gear. The fol- lowing may be said to be the principal requirements for a successful breech mechanism : Safety, Ease and rapidity of working, Not easily put out of order, Ease of repair, Inter changeability. The breech mechanism comprises the breechblock, the firing mechanism, and the mechanism for the insertion and withdrawal of the block. There are two general methods of closing the breech. In the first method the block is inserted from the rear. The block 34 is provided with screw threads on its outer surface which engage in corresponding threads in the breech of the gun. In order to facilitate insertion and withdrawal of the block the threads on the block and breech are interrupted. The surface of the block is divided into an even number of sectors, and the threads of the alternate sectors are cut away. Similarly, the threads in the breech are cut away from those sectors opposite the threaded sectors on the block. The block may then be rapidly inserted nearly to its seat in the gun, and when turned through a comparatively small arc, say one-eighth or one-twelfth of a circle, depending upon the number of sectors into which the block is divided, the threads on the block and in the breech are fully engaged and the block is locked. In the second method a wedge-shaped block is seated in a slot cut in the breech of the gun at right angles to the bore, and slides in the slot to close or open the breech. Variations of these two methods will be noted in the detailed descriptions of the guns which follow. The most notable variation from the above two types is the Nor- denfeld type of breech mechanism, a rotating block construction found on the French 37-millimeter and 75-millimeter guns, de- scribed more fully and illustrated in the description of these guns. The breechblock is usually supported in the jacket of the gun or in a breech ring screwed into the jacket. The seat in the jacket being of greater diameter than could be provided in the tube, the bearing surface of the screw threads on the block is increased and the length of the block may be diminished. The slotted screw breechblock is used to a great extent in our service. Its advantages are uniform distribution in the gun of the longitudinal stress produced by the powder pressure and lightness permitted in the construction of the breech end of the gun. In the model of 1917, 3-inch antiaircraft gun, however, and in the Ameri- can 75-millimeter gun, the sliding block operating vertically has been adopted for the reason that it permits of simpler mechanism for semiautomatic operations. INTERIOR BALLISTICS treats of the motion of the projec- tile while still in the bore of the gun. It includes the study of the mode of combustion of the powder, the pressure developed, and the velocity of the projectile along the bore of the gun. MOUNTS FOR MOBILE ARTILLERY. A modern gun carriage is expected to stand steady on firing, so that in the first place it requires no running up, and in the second place it maintains the direction of the gun so that only a slight cor- rection in elevation and direction is required after each round. The carriage is maintained in position by the spade, which sinks into the ground, and by the friction of the wheels upon the ground. If the force of the recoiling gun were communicated directly to the anchored carriage the effect would be to make it jump violently, which would not only disturb the lay, but would prevent the cannoneers from maintaining their position. The hydraulic recoil brake is therefore interposed between gun and carriage. If the gun were rigidly attached to the carriage, the latter would be forced back a short distance at each round, and the whole of the recoil energy would have to be absorbed in that short motion. In- stead of this, the gun alone is allowed to recoil several feet on the carriage and although the recoil energy is in this case greater than it would be if gun and carriage recoiled together, yet it is so grad- ually communicated to the carriage that instead of a violent jerk we have a steady, uniform pull, the only effect of which is to slightly compress the earth behind the spade. In a well-designed carriage the amount of this pull should not greatly exceed that required to lift the wheels off the ground by rotating the carriage about the spade and must be less if complete stability is required. The only motion of the carriage which takes place is that due to the elastic bending and rebound of its parts under the strain set up in discharge. These strains are inevitable since the direction of re- coil can not be always exactly in the line of the resistance of the earth behind the spade. This movement of the axis is known as " jump " and must be determined by experiment for the individual piece in its particular mounting as it is affected by many features of construction. The principal parts of the typical gun carriage are the recuperator ; the top carriage; the trail; the wheels and axle. The gun slides in recoil on the upper surface of the recuperator which contains the recoil controlling parts. In the design of the carriage the constructional difficulty lies not so much in preventing the carriage from recoiling, but in preventing (85) 36 the wheels from rising off the ground at the shock of discharge. The force of the recoil of the gun tends to turn the carriage over backwards about the point of the trail or center of the spade. This force is resisted by the weight of the gun and carriage, which tends to keep the wheels on the ground. The leverage with which the overturning force acts varies with the distance of its line of action above the center of pressure on the spade; the leverage with which the restraining force acts varies with the horizontal distance of the center of gravity of the gun and carriage from the center of pressure on the float. It follows that the steadiness of the carriage for a given muzzle energy may be promoted by four factors : (a) Increasing the weight of the gun and recoiling parts. This reduces the energy of recoil. (&) Increasing the length of recoil allowed. This reduces the overturning pull. (OOOOOOOOOO( 1 fl oooooooooo IOOOOOOOOOOC \ TDOO oooo o o o o \_ " oo o o o o o o o o oj_ V _>OOOOOOOOO O(f Jo o o o o o o o o o or I FIG. D. FIG. E. In figures H and J the recuperator piston (P) forces the oil from the recuperator cylinder into the gas reservoir through the port (A) when the gun recoils. Thus the gas is compressed and the necessary energy stored up to return the gun to battery. The SRRIMC3 FIG. F- IM-BATTERX OR F1RIMC3 EINP OF" F?EICOII - SF>RIMG REICOli-. piston may be attached to the gun and move with it, the cylinder being fastened to the carriage, or the cylinder may move and the piston rod be fastened to the carriage. The gas is given sufficient initial compression to hold the gun in battery at all elevations. 42 The type of recuperator shown in figures K and L is similar in operation to that of figures H and J, but in the latter design the oil is separated from the gas by the floating piston (FP). FIG. H IN-BA-rTETRV OR F"IRIINQ f=>OSmorS FLOATING PISTON FIG. U E/NP OF" RETCOIL- MVPRO-PrSETUMAT-IC REICOIL- SVSTEM WITH F-t-O/VTlMCS F^lS-rOTH RG. K IN-BATTETRV OR posmofN AIR ruuio FIG. HVDRO- PNEUMATIC RECOIL- SVST'EIN'I WITH FT_UIP IM PiREicrr corsTAOT WITH THE: >AIR The hydropneumatic recuperator (or counterrecoil mechanism) may be separated from the recoil brake or the two may be combined in one unit. OIL .43 The principal advantages of air cylinders over spring cylinders for counterrecoil are the reduction in weight and longer life. These advantages are especially important in long-recoil field guns or how- itzers designed to be fired at high angles of elevation. If springs are used the columns are long and heavy, being liable to breakage ; while if air cylinders are used, the additional pressure needed when the guns are fired at high angles of elevation can be obtained by pumping more air into the cylinders. It is evident that the energy, in whatever way obtained, which effects counterrecoil, forms a part of the total energy of recoil. The total resistance to recoil is composed of the resistance offered by the brake, the resistance due to friction, the resistance either plus or minus due to the inclination of the top of the chassis or the recoil slides, and the resistance due to the counterrecoil springs or air cyl- inders, if there are such included in the recoil system. The counterrecoil buffer is , provided for reducing the shock / to the carriage as the gun is re- . turned to the firing position by FIG M. the counterrecoil mechanism. In figure M is shown a type of buffer which is used to some extent. It consists of a rod (B) which acts inside the hollow piston rod of the recoil cylinder. A method similar to this is to provide a separate cylinder in which a projection of the recoil piston acts during the last few inches of recoil. It may consist of a dashpot formed at the end of the recoil cylinder. The use of the counterrecoil buffer increases the stability of mobile artillery carriages by preventing their forward motion as the gun runs into battery. Modern field guns and howitzers are mounted so as to have a long recoil on their carriages when fired horizontally. When certain types of these guns are fired at high angles of elevation it is necessary to reduce the length of recoil to prevent the breech of the gun from striking the ground. This reduction is effected by a mechanism which automatically reduces the size of the orifices in the hydraulic brake as the gun is elevated. This is known as variable recoil. If no counterrecoil buffer is provided, the velocity of the gun when going into the firing position under the action of the counterrecoil springs or air cylinders is at a maximum just as it reaches that posi- tion. If an arrangement is made to automatically fire the gun when it has this maximum forward velocity, it is evident that the maximum velocity of free recoil will be reduced by the amount of the forward velocity, and hence either the total resistance or the corresponding length of recoil, or both, can be materially reduced. Systems based 44. upon this principle have been used abroad for small guns, such as mountain guns. The gun is caught by a pawl in the extreme recoil position and is loaded in that position. When it is desired to fire, the pawl is tripped, the gun runs forward and is automatically fired as it reaches the firing position. The principal objections to this system, which is known as the differential recoil system, are the unsteadiness of the gun at the moment of firing and the possibility of the gun being turned over in a forward direction by the shock of counterrecoil if a misfire should occur. In artillery of position, the gun carriage is rigidly bolted to a fixed platform. Its mechanism is such as to allow the gun and the attached parts to recoil on firing. The hydraulic brake cylinder and its piston are attached, respectively, to the moving and fixed parts of the car- riage, or vice versa, in such a way as to cause the piston to be drawn through the cylinder as the gun recoils. When constant total resist- ance is to be exerted by the recoil system, which is always the case in artillery of position, either the total resistance or the length of recoil may be assumed, and the other determined. While the assumption of a very long recoil would reduce the resistance and consequently the strain on the carriage and permit its parts to be made lighter, the necessary increase in the length of the recoil slides might overbalance the saving in weight. In carriages, such as mortar, antiaircraft gun, and the latest type barbette carriages, all of which permit the firing of the gun at high angles of elevation, a very long recoil can not be used, because the distance from the breech of the gun to the supporting platform will not permit it. Furthermore, the use of a long recoil would necessi- tate the use of long and heavy columns of counterrecoil springs. Lack of space also prevents the use of a long recoil on turret mounts. In disappearing carriages, the length of recoil is determined more by the necessity of giving the gun the proper movement in recoil than by limitation of the strains brought upon the carriage. With the exception of the disappearing and the older type of barbette carriages, the recoil for artillery of position is comparatively short. The construction of all modern wheeled carriages is such as to allow the gun to recoil in the direction of its axis. The resistance to recoil developed by the recoil system pulls forward on the gun and backward on the carriage, tending to move the latter to the rear. Actual motion of the carriage to the rear is prevented by a spade sunk in the ground at the end of the trail of the carriage and so con- structed as to present a broad surface to the ground in the rear. Under ordinary conditions the ground will resist a pressure of 40 pounds per square inch of spade surface, and knowing the pressure 45 developed by the pull of the piston rod, which is the only force acting on the carriage, the size of spade can be determined. Another effect produced by the resistance to recoil is a tendency to rotate the carriage around the point of support of the trail, or to cause the wheels to jump from the ground. Such a movement is very undesirable, as it interferes with the rapid aiming and firing of the piece. In order to prevent the wheels from jumping off the ground when the gun is fired, it is necessary that the product of weight of the carriage, including its recoiling parts and the hori- zontal distance of the vertical through their center of gravity from the point of support of the trail, should at any instant be greater than the product of the force opposing recoil and the perpendicular distance from its line of action to the point of support of the trail. The value of the total resistance to recoil, that will be just insufficient to cause the wheels to rise from the ground when the gun is in the firing position, is obtained by equating moments which will show that a value of this resistance small enough to prevent jump of the wheels in the early part of the recoil might still cause jump toward the end of the recoil, as the moment of the weight of the recoiling parts becomes less. It is evident that safety against jump can be maintained and the necessary length of recoil shortened if, instead of assuming a constant total resistance, we assume it as decreasing to such an extent as to remain parallel to a line showing the maximum permissible values of the total resistance to recoil and plotted as a function of the length of recoil. If the length of recoil is such as to provide a factor of sta- bility when the gun is fired at horizontal, the carriage will be stable at all higher elevations, as the lever arm of the total resistance of recoil decreases as the gun is elevated. For this reason reduction of the length of recoil with increase of elevation in howitzer carriages does not impair their stability. The initial strength of the counterrecoil spring columns or air cylinders is the force which they exert against the gun in the firing position. This force must be great enough to hold the gun in that position at the highest angle of elevation at which it is to be fired, as well as to overcome the friction on the recoil sides as the gun runs forward to jthe firing position. AIMING DEVICES AND SIGHTING METHODS. Sights will be discussed briefly in this handbook merely to indi- cate their application to field, antiaircraft, and trench materiel. In order that a projectile from any gun may hit the target, the gun must be fired at a certain angle of elevation depending on the range, the ballistic characteristics of the gun, and upon the relative difference in level of the gun and target. It must be given such a direction to the right or left of the target as to offset the deviation of the projectile due to drift and wind. The sights of the gun provide means of determining when the axis of the gun has the predetermined direction. When the piece is sighted, both in elevation and direction by sighting directly on the target, the method is known as direct laying. This is precisely the same operation as sighting a shoulder rifle or pistol. The line of sight may be fixed in one of two ways. The first method is to use plain or open sights, the rear one of which has a peep, or notch, capable of adjustment in a vertical or horizontal direction. This rear sight is equipped with an arc reading in frac- tions of the range, or degrees of elevation, by, which the necessary elevation can be set off. In some cases the rear sight is designed to automatically correct for drift ; if not, the drift must be set off on a scale provided for this purpose on the rear sight. It is always well to bear in mind that the flight of the projectile follows the movement of the rear sight, going higher as the sight is raised, and to the right or left as the sight is moved to the right or left. The second method for direct laying is to use a telescope with cross hairs which takes the place of the open sights, although the principle of operation is the same. The angle of elevation of a gun must be measured in the vertical plane through the axis of the piece. It frequently happens that a mobile piece must be fired under conditions in which the axis about which it turns in elevation (trunnion axis) is not level, thereby throwing the sight plane out of the vertical. If this is the case, the sight arm must be revolved about an axis parallel to the axis ^of the gun until the sight arm is vertical. Most wheeled mounts have such a provision made on their sights. Independent Line of Sight. In order to relieve the gun pointer from the necessity of set- ting the elevation on the sight standard and elevating the piece, some guns are provided with what is known as the independent line (46) 47 of sight. It will be noted that the actual quadrant elevation of the piece consists of two parts : (a) The elevation necessary to reach the target if it were on the same level as the gun. (Z>) The correction to this elevation required by the difference in level of the gun and target (angle of site). With the independent line of sight the two parts of the quadrant elevation are applied to the gun independently. An intermediate rocker and two elevating systems, A and B, are provided as shown in Figure N. The sight is fixed to the rocker, and for direct fire the gun pointer manipulates the lower elevation system A, which moves the rocker as well as the gun in elevation. In this way the angle of site is auto- matically corrected, when the line of sight is brought upon the target. The other elevating mechanism, B, is between the rocker and the gun and is manipulated by another cannoneer, who elevates the gun until the proper range appears on a range scale. The change in range does not affect the setting of the lower elevating mechanism, and the gun pointer is thus free to devote his whole time to keeping his line of sight upon the target and is not compelled to take his eye from the telescope. The additional mecha- nism necessary for this system is more than offset by the ease of manipulation secured. Various modifications of this general method of securing the inde- pendent line of sight are in use and will be discussed with the guns to which they pertain. The gun is said to be laid indirectly when it is laid by means other than aiming directly through the sights at the targets. The fire from modern fieldpieces is so accurate and destructive that it is always necessary to establish field batteries in position out of the view of the enemy for the sake of protection. Indirect sighting is then the usual method of sighting such guns. The panoramic sight affords the means of aiming the gun in indi- rect laying by directing the line of sight on any object in view from the gun; at the same time it affords the advantage of a telescopic sight in direct or indirect aiming. This panoramic sight is a telescope so fitted with a rotating head, reflectors and prisms, that a magnified image of an object anywhere in view may be brought to the eye without change in the position of the observer's eye. 5516021 4 48 The panoramic sight is often mounted in connection with the range- sighting mechanism, but in some cases in order to divide the duties of laying for direction and elevation, the panoramic sight is mounted on a shank on the left side of the cradle and used in laying for direc- tion, while the range quadrant for laying in elevation is placed on the right side of the cradle and used by another cannoneer. In connection with the range quadrant a range level is provided, which is a special form of clinometer. It is used in setting off the angle of site, thereby correcting for difference in level of the gun or target. The range quadrant is graduated in units of angular eleva- tion or in fractions of the range. In the case of howitzers the different zones of fire are sometimes shown. While the use of the range quadrant separates the duties of the cannoneers in aiming, it does not comply with the conditions for the independent line of sight. The sight and range quadrant being attached to the cradle, both move in elevation with the gun. The independent line of sight per- mits of the gun being moved and set in dSiffi&lM ^J^ j elevation without any change in position K j of the sight used for direction aiming. Leveling plates or similar surfaces are provided on all guns and howitzers on which a gunner's quadrant (see p. 49) can be used in obtaining or checking the elevation. It is not the intention to go into detail in this handbook regarding the fire- control equipment employed for direct- ing the fire of antiaircraft materiel, but as the development is so new, and they are so closely involved with artillery during operations, it is quite necessary to devote some space to the fire-control equipment. Many of the terms and instruments used in connection with anti- aircraft artillery are similar to those employed with field artillery materiel, but the methods of application in most cases differ. In the direct fire of antiaircraft artillery the following angles resulting in the laying of the gun to the predicted future position of the target are involved : 1. Present azimuth and elevation. These are obtained by direct sighting upon the target. 2. Principal lateral and vertical deflections. 3. Secondary lateral and vertical deflections. 4. Superelevation. PANORAMIC SIGHT, MODEL OF 1917. 49 In the determination of the principal lateral and vertical deflec- tions, two methods of fire control have been established : 1. Linear speed. 2. Angular speed. Each method assumes rectilinear travel of the target i. e., that the pilot of the aircraft will fly a straight course at unchanging speed and constant altitude during the time required for the deter- mination of the fuse range, setting of the fuse, loading and firing the gun, and for the projectile to reach its point of burst. Each method is based upon sound mathematical reasoning and involves automatic apparatus of rather complex but easily operated mechan- GUNNER'S QUADRANT, MODEL OF 1918. ical and electrical design, in order to resolve the data required in the laying of the gun. In the first method the quantities required in the resolution of the formulae are : (a) Presentation (angle of approach) ; i. e., the horizontal pro- jection of the angle made between the vertical plane of sight and the axis of the fuselage of the airplane. (5) Engine speed of the target. (c) Altitude of the target. (d) Time of flight of the projectile to the future position of the target. 50 The resolution of the formulae deriving the lateral and vertical deflection corrections is accomplished upon a device known as "Antiaircraft artillery deflection computer." The readings ulti- mately obtained from this instrument are given in mils. They are transmitted telephonically or by direct announcement to the gun layers who immediately lay the gun to its future position, while the telescope pointers remain sighted upon the present position of the target. The great advantage of this method lies in the fact that the pre- sentation and engine speed can be estimated with reasonable ac- curacy. The altitude of the airplane is determined from altimetry stations, and the time of flight is known when fuse range has been determined from a telemeter. In the angular speed method the lateral and vertical angular velocity of the target is measured. These are multiplied by the total element of time mentioned in the aforesaid and gives the respective displacements. The fact that the angular velocity of an airplane in ordinary flight is never uniform makes this method more difficult of apprehension but, as applied in our instrument design, gives results appreciably better than the linear speed method and is consequently used more generally. The instruments resolve the lateral and ver- tical deflection corrections in mils and also the fuse, range. These are telephoned to the gun layers who function the sighting system mechanisms. The element fuse range is required for two main purposes in anti- aircraft gunnery: (a) For the setting of the fuse, and (5) as a func- tion in automatically giving superelevation to the gun i. e., the angle between the line of sight to the predicted future position of the target and the axis of the bore of the gun when ready to fire. Secondary deflections are required in making allowances for wind- age, ballistics, drift, etc. These are set by giving secondary move- ment to mechanisms of the sighting system. When firing, " indirect " or at night, which essentially is indirect fire, three elements pertaining to the predicted future position of the target are transmitted from this apparatus at the fire-control station in order to accomplish the laying of the gun and setting of the fuse : 1. Azimuth. 2. Quadrant elevation. 3. Fuse range. Secondary deflections involve, in addition to those common to direct firing, corrections for parallax when firing " indirect." At night the alliance of listening apparatus and searchlights assist in accomplishing the resolution of the gun-laying elements at the fire-control station. 51 Altimetry, which is a basic factor in the computation of the prin- cipal and secondary deflection corrections, is obtained in one of two ways : (a) Monostatic. The monastatic or one-station instrument is an optical device that determines the altitude by automatic triangulation through the coin- cidence of light rays along a self-contained base. (b) Bistatic. This is a system in which two stations are set up and oriented along a base line of known length, frequently as great as 4,000 yards. The height or vertical distance of the target above the base line is then determined geometrically by projecting its altitude horizontally into the vertical plane passing through this base line. When altitude has been determined, the observed position is resolved into the future position by automatic devices. When firing against airplanes at night, searchlights are used to illuminate the objective. When it is able to find it and keep it in its field, firing can be conducted in the same manner as in day- time. Many sound-detecting instruments have been made; one of the recent types is the " Paraboloid." A surface in the shape of a paraboloid, movable in azimuth and site, focuses the sound waves when its axis is placed in their direction ; they swing from one side of the focus to the other when the axis of the instrument is turned. The sound is received by trumpets placed on either side of the focus and joined in pairs to the ears of two observers who adjust the instrument, the one for azimuth, the other for site. Briefly, the foregoing describes the fundamentals of anti-aircraft artillery fire-control methods. Being the most precise form of gunnery, anti-aircraft artillery involves material capable of the highest degree of facility and accuracy in the automatic measure- ment of deflections and the maneuvering of its gun-laying mechan- isms in order that effective fire may be conducted against a target whose movements are subject to such large displacements. (See Ordnance Document No. 2037, " The Manufacture of Optical Glass and of Precision Optics"} (See War Department Document No 1065, "Handbook on Elemen- tary Optics and Applications to Fire-Control Instruments") 52 ACCOMPANYING VEHICLES. In addition to the piece itself, a number of vehicles are necessary in batteries, sectors, and regimental organizations of field artillery for maneuvering and serving the piece. The type of vehicles vary with the different guns and the various organizations. Some of the more common vehicles such as limbers, caissons, etc., are described in a general way in this chapter, while their special features are described in detail with the materiel with which they are issued. Other special vehicles such as reels, store and battery wagons, etc., are also described with the materiel to which they pertain. The caisson is essentially a conveyance for the transportation of ammunition in the field. It generally consists of a chest for ammu- nition mounted on two wheels and an axle. In front it is fitted with a short pole having a lunette for attachment to other vehicles and in the rear with a pintle, to which additional vehicles may be attached. Various tools are usually carried on the caisson, and seats are pro- vided for the accommodation of the personnel. The limber is a two-wheeled vehicle designed primarily to increase the mobility and facilitate the maneuvering and deployment of field artillery. There are several types of limbers in use, the principal ones being the carriage and caisson limbers. The carriage limber is attached to the trail of the piece when traveling. For light field pieces, a chest for ammunition is pro- vided on the carriage limber. In the case of heavy pieces, the chest is dispensed with and the trail of the piece rests on the top section of the limber. A pole is provided at the front for horse or motor traction, and the rear is equipped with a pintle for attachment of the carriage. The caisson limber is used for hauling the caisson and is provided with a chest for carrying ammunition. The forge and store limbers are designed to carry supplies and equipment, the forge limber carrying the tools and supplies for the farriers' shop. The battery wagon and the store wagon are two- wheeled vehicles equipped with chests for tools, supplies, and spare parts. With batteries of heavier field artillery, some of the vehicles are dispensed with, especially the caissons, battery wagons, forge, and store limbers, the ammunition being carried in motor trucks, in which most of the spare parts and supplies are also carried. (53) 54 Light field artillery is usually drawn by horses although some of these batteries are now motorized; i. e., hauled by either caterpillar tractors or motor trucks. In addition to this, provisions are made for a limited number of trailers for use in carrying light guns at high speed behind motor vehicles. These trailers are rubber tired and for high-speed condi- tions ; the complete gun, with carriage, may be placed on this trailer instead of being transported on its own wheels. The recent struggle in Europe brought about problems which heretofore have never existed in warfare; and to meet these, changes have been made in every arm of the service, the greatest and 75-MILLIMETER GUN CARRIAGE MOUNTED ON A 3-INCH FiELD GUN TKAlLt-R. most radical change being the motorization of artillery. Mechanical transport is at this time in such a state of development that there is no need of dwelling upon its numerous advantages over animal draft. The original heavy artillery was limited to guns emplaced in permanent fortifications and guns of large caliber which were only moved with great difficulty. Light horse-drawn guns and howitzers comprised the mobile artillery for use in the field. This type of artillery was ideal for quick action at short ranges. As the artillery became a more important factor, large caliber long- range jruns were required. The movements of this heavy artillery in 55 the field could only be accomplished in one way by motorizing it. The result is the development of the extremely mobile heavy artillery. In applying motor transportation to artillery, types of motor vehicles of widely varying capacity and duty are required. In most cases commercial cars and trucks are used, but in a few instances special types have been developed. Motor equipment is still under- going changes, all tending to produce apparatus of unfailing depend- ability and maximum mobility and flexibility. Motor apparatus of the following types have been selected as the most suitable for accomplishing this motorization : First, passenger cars, both light and heavy; second, motor cycles with and without side cars; third, trucks; fourth, four-wheeled trailers; and fifth, tractors of the caterpillar type. Passenger cars are furnished when on. the march and when occupy- ing a position on the lines. Batteries are supplied with light touring cars, staff cars, and motor cycles with side cars. Battalion and regi- mental headquarters are also supplied with light touring cars and Westfield military bicycles. A motor cycle is ideal for liaison and work of similar nature requiring rapid transportation for one or two individuals. The motor cycle is particularly useful when trav- eling in convoy and for keeping the various units of an organization in close touch with each other. Motor trucks are necessary for carrying supplies and ammunition from the depots and distributing them to the various units. A great many trucks are required to insure unfailing supplies when artillery is in action. Because of the uncertain conditions of the roads back of the lines sturdy trucks that can. pull through under the most unfavorable conditions are employed. In bringing the guns into position it is often necessary to cross ground plowed by exploded shells, to go through mud and deep sand, and to ford streams which can not be negotiated by a wheeled type of motor vehicle, thus the type of apparatus adapted for this purpose is the caterpillar tractor. The problem of the care and maintenance of motor equipment in the field is met by issuing the repair and artillery supply trucks to each battery supply and headquarters company of motorized artillery. The artillery supply truck is really a motorized store wagon carry- ing spare parts, tools, etc., for the particular kind of unit to which it is assigned. The artillery repair truck consists of a small machine shop mounted on wheels. Its equipment is complete, including a lathe, drill press, air hammer, forge, etc. Electric power is supplied by a small gen- erator driven by an individual gasoline motor mounted on the truck. The equipment is designed to make all repairs in the field, both to artillery materiel and motor vehicles. 56 The motor equipment makes transportation a comparatively easy matter, permitting it to be moved with rapidity, either on the offensive or defensive. The value of this equipment becomes more apparent as the nature of warfare changes from that of position to that of movement. Detailed descriptions of the above motor vehicles are given in separate handbooks pertaining to motor equipment materiel. (See War Department Document No. 101$.) 37-MILLIMETER GUN MATERIEL, MODEL OF 1916. Experience has shown that the infantry can not carry out its mis- sion by its rifles and machine guns except at prohibitive loss of per- sonnel. The individual rifle does not offer the necessary volume of fire, while the rifle grenade, and even more so the hand grenade, is a close-combat weapon. Hence the taking of a machine-gun nest by a unit (consisting of an automatic rifle squad, hand bombers, and rifle grenadiers) attacking the flanks will not prove very successful, particularly if machine-gun nests are echeloned to considerable depth and executing cross fire. Such condition calls for some form of artillery, effective at from 400 to 1,500 meters, against both personnel and materiel, and capable 37-MILLIMETER GUN CARRIAGE AND AMMUNITION CART, LIMBERED. of immediate action. The field artillery is not available because of difficulty of communication and length of time necessary to get into action. The heavy artillery is not sufficiently mobile. Its dispersion is too great for small, definite targets, thereby calling for vast amount of ammunition, extremely difficult to transport. The necessity of providing an accompanying gun for certain units of infantry has led to the adoption of a 37-millimeter gun (devel- oped by the French Army). The 37-millimeter gun, also known as the 1-pounder or infantry accompanying gun, is the smallest weapon of the field-gun type in use by the American Army. It is used by advancing infantry outfits, chiefly for destroying concrete machine-gun emplacements, outposts, and other points of resistance. Recent developments and modifica- tions of this weapon have found wide application for its use and, due to its extreme portability, this gun is adaptable for tanks, tractors, and aircraft. (57) 58 As this gun is intended to follow infantry over any kind of ground its construction is designed to give great mobility. The personnel is organized for rapid fire; the possible rapidity of fire is 35 shots per minute. Each gun unit is composed essentially of two elements : (1) The gun on a tripod mount, capable of being set on wheels. (2) A light wagon serving as a limber and carrying ammunition, spare parts, and accessories. The gun and limber when joined are normally hauled by one horse or mule, but near the enemy they are separated and moved by man. In action the gun is operated by two men, one keeping it on the aiming point and the other loading and firing. The gun must be cocked by hand in order to load for the first round, but thereafter the counterrecoil of the barrel cocks the piece, and it is only neces- sary to open the breech mechanism, which ejects the case, insert a new cartridge, close the breech, and fire. When used as a tripod mount, it is separated into portable groups for transportation and each unit is carried by two men. One group, weighing 104 pounds, consists of the gun and cradle and the other of the trails, weighing 84 pounds. With the combination tripod mount,, the gun is transported on a wheeled carriage which is limbered to a two- wheeled ammunition cart, drawn by one mule or horse. Wcigths, dimensions, and ballistics. Weight of gun and recoil mechanism (with flash hider and sight) -pounds 104 Weight and recoil of group do 34 Weight of barrel group __do__ 38 Weight of breech group do 18 Weight of flash hider do 2. 5 Length of gun calibers 20 Range (H. E. Shell Mark II) meters 3,650 Muzzle velocity feet per second 1.204 Weight of projectile pounds 1.234 Length of recoil inches 7-10 Maximum angle of elevation degrees 21 Maximum angle of depression do 14 Amount of traverse to right '__ do 22 Amount of traverse to left do 16 Weight of axle, complete pounds 36. 25 Weight of wheels, each do 68 Weight of trails (including pintle and float) do 84 Diameter of wheels inches 37.75 Width of track do 33 Weight of gun and carriage, complete pounds 360 Over-all length of vehicle inches 75 Over-all height of vehicle do 37. 75 Over-all width of vehicle.. do 57 59 60 The gun is composed mainly of a steel alloy barrel. A front clip of bronze and an aluminum jacket serve as supports and guides for the whole barrel. The breech housing is screwed to the rear end of the barrel and forms a receptacle for the breechblock. The breechblock is of the Nordenfeld type and with the exception of size is practically the same as that used on the French 75 milli- meter field gun. It screws into the breech housing and is opened and closed by being rotated 156 degrees about its axis, which move-, ment is limited in each direction by a stop. The breechblock is cylindrical in form, rotates in a threaded seat and is operated by a handle which when moved to the left causes the eccentric hole in the block to register with the bore and also operates the extractor thus ejecting the empty cartridge case. Pulling the lever to the right rotates the block so that the port in the block is drawn away from the bore and a solid surface containing the firing pin backs up to the base of the cartridge. The action of the powder gases on the breechblock at the moment of discharge produces the recoil of the united barrel and breechblock. TRIPOD MOUNT IN* FIRING POSITION. The purpose of the recoil mechanism is to control and limit the recoil and to return the barrel to the firing position,. at the same time pre- venting a sudden return which might disturb the aim of the gun. The recoil cylinder consists of a cylinder containing a piston, piston valve, counterrecoil spring in three sections, and counterrecoil buffer. The piston rod, which is hollow and open at the piston end, is pierced with holes for the passage of oil both during recoil and counterrecoil. The piston is fitted with four holes for the passage of oil during recoil. This oil is allowed to pass through two parts of the piston ; first, through the hollow portion of the piston rod, and second, through the holes in the piston head. The oil passages in the piston head are closed by the piston valve. The valve is held against the front face of the piston by a spring, closing the oil holes in the head during the counterrecoil stroke, thus slowing up the for- ward motion of the gun. The counterrecoil buffer is screwed into the front cylinder cap and eases the movement of the gun into battery, thus preventing excessive shock. The capacity of recoil cylinder is 2.75 pints and the extreme travel of the piston is 11 inches. 61 The mount may be used either in the form of a tripod or with the axle and wheels attached. In the former case a front leg having a float adjustable to two heights at its lower end is used to support the front end of the mount, and the spread trails in rear equipped with spades form the other points of support. In the case of the wheels being used, the front leg is swung up and secured, and both trails are spread out to support the rear. The pintle, or gun mount, is in the form of a yoke, the upper end being fitted to receive the cradle trunnions. Each trail head is equipped with lugs which pivot on bearing surfaces in the lower end of the pintle. The trails, when spread, are kept in position by a removable transom, which also serves as a seat for the gunner. A Y-shaped frame, pivoted and secured to the pintle at its upper and lower ends, extends to the rear in the form of a fork and engages the nut housing on the traversing screw. The nut is turned in its housing by a small handwheel attached thereto, which causes the GUN DISASSEMBLED ON THE MARCH (WHEELS AND AXLES LEFT IN THE REAR). nut and housing to move along the screw, thereby traversing the gun. The screw is pivoted in the left trail and moves in and out through a bushing pivoted in the right trail when the trails are being spread or closed. When the trails are to be closed, the gun is trav- ersed to the extreme right. The elevating mechanism is located on the frame in front of the traversing mechanism. A screw fitting into a nut pivoted in the frame is raised and lowered by a handwheel attached to its upper end. Above the elevating handwheel is a hook engaging a pin fitted to the underside of the cradle, thus the rear end of gun is secured to the trail and the elevation accomplished when the cradle is mounted in the trunnion bearings. A conical sheet metal flash hider is secured to the muzzle of the gun. Some of these carriages are equipped with an armor plate shield, suitably reinforced by stiffeners. The shield consists of three plates hinged together, and is mainly employed to protect the gun- ners from shrapnel and flying fragments. 62 The gun is provided with a telescopic sight for use in direct fire and a quadrant sight for indirect or masked fire, either of which is mounted on the left side of the gun and in a bracket which is part of the striker rod housing. The wheels are 37.75 inche% in diameter and have steel tires 1.875 inches in width. The ammunition is of the fixed type having a steel projectile weigh- ing 1.097 pounds containing high explosive, and detonated by a base percussion fuse. A complete round of ammunition weighs 1.47 pounds and is composed of projectile, brass case, primer, and powder charge. GUN AND PERSONNEL ON THE MARCH (AMMUNITION CART LEFT IN THE REAR). AMMUNITION CART FOR THE 37-MILLIMETER GUN. The 37-millimeter gun limber (of the machine gun ammunition wagon type) is essentially a frame resting on two shafts having a movable bolt and rear fittings by means of which it can be joined to the gun mount. The limber carries 14 ammunition boxes, each containing 16 car- tridges packed in a fiber packing strip. There are also provided 2 wooden boxes for carrying spare parts, tools, accessories, etc. 2.95-INCH VICKERS-MAXIM MOUNTAIN GUN MATfiRIEL. WITH PACK OUTFIT. The 2.95-inch Vickers-Maxim mountain gun materiel is of Vickers design and American and British manufacture. This materiel is intended for transportation by pack animals; for this reason it is a light, compact weapon, separating very quickly and easily into four loads for packing. The cradle is carried as one load, the wheels and axes as another, the trail another, and the gun as the fourth. Four other pack animals carry the pioneer tools, blacksmith's tools, supply chest, and signal tools, respectively. Additional pack animals are employed to carry the ammunition for the battery. Suitable pack frames with all the necessary attachments are provided for holding the load compactly and in proper place on the animal. Weights, dimensions, and ballistics. Caliber mches__ 2.953 Length of gun '. do 35. 85 Weight of gun, including breech mechanism pounds 2"-6 Rifling uniform, 1 turn in 25 calibers, right-hand twist. Weight of projectile do 12J Weight of power charge ounces 8 Muzzle velocity I: feet per second 920 Maximum range , yards 4, 825 Length of recoil of gun inches 14 Height of axis of gun above ground do 26 Maximum angle of elevation degrees 27 Maximum angle of depression do 10 Amount of traverse of gun on carriage do Diameter of wheels inches 36 Width of track do 32 Weight of carriage only pounds 595 Weight of gun and carriage do 830 The gun barrel is a one-piece steel forging, cylindrical in form. On either side of the breech end two lugs are provided to which the piston rods are secured when the gun is mounted in the cradle. For- ward of these lugs is a finished surface of uniform diameter which constitutes a bearing for the gun. This surface is supplemented at the forward end of the gun by two collars of equal diameter, thereby 5516021 5 (63) 64 insuring a firm bearing for the gun in the cradle, either in recoil or in battery. At the bottom of the barrel is a guide which slides in a corresponding groove in the cradle, thus keeping the gun in proper position and preventing it from turning when in action. The breech mechanism is of the interrupted-screw type. A handle which operates from left to right turns and swings the block clear with one motion. The firing pin is operated by means of a trigger which is pulled by the firing lanyard. A safety device is incorporated to prevent firing when the breech is not closed. The breech is equipped with an extractor which ejects the empty cartridge case after firing. 65 The recoil mecJianism is of the hydrospring type. It is known as the short-recoil type in which the gun is permitted a length of recoil upon the carriage, sufficient to diminish the movement of the carriage on the ground but not sufficient to render the carriage stable. To u 3 Z 3 LJ J I J U U I y retard the movement of the carriage on the ground the wheels are locked by means of " brake ropes," which lock the wheels to the traiL Two buffer cylinders, one on each side of the gun, are bored in the cradle casting. They contain both the recoil and counterrecoil mechanism. The cylinders are connected at the rear by a by-pass which keeps the oil pressure equal in the two cylinders. Throttling 66 1 is obtained by grooves of varying width in the cylinder liners. The piston rods are attached to the gun by means of interrupted screws, which permit quick removal for transportation. The counterrecoil mechanism consists merely of springs wound around the piston rods, which are compressed on firing and which return the gun into battery. REAR VIEW OF CARRIAGE. The cradle is a bronze casting comprising three parallel cylinders. The central cylinder supports the gun from the breech to within a few inches of the muzzle. The other two, as before stated, accommodate the recoil mechanism. In place of trunnions there are two lugs underneath the cradle through which passes the cradle axis bolt, by means of which the cradle is secured to the trail. This bolt is pro- vided with a handle and suitable catch for quick removal when 67 disassembling for packing. The cradle also carries the sight bracket and has a plane surface on top, on which the gunner's quadrant may be used. The elevating gear consists of a quadrant with a worm wheel segment thereon operated through suitable gearing by a handwheel DETAILED VIEW OF GUN. on the left side of the trail. A bolt for quick release of the elevating mechanism from the cradle is provided. Elevations from 10 degrees depression to 27 degrees elevation may be obtained. SIDE VIEW OF CARRIAGE IN BATTERY. No traversing mechanism is provided, and traverse must there- fore be obtained by swinging the trail. The trail consists of two steel side plates connected by crosspieces and transoms. The front crosspiece contains bearings for the axle, cradle axis bolt, and elevating gear. A shoe at the rear end of the 68 trail is fitted with a "scraper," which in reality is a short spade. It is also provided with a socket for the handspike. The axle is a solid cylindrical bar with flats cut on two sides for securing it in the front crosspiece of the trail. It is quickly removable for packing and is carried on the same pack animal as the wheels. The wheels are 36 inches in diameter and are steel tired. Sighting is accomplished by means of the sight, model of 1912, combined with either an open sight or the panoramic sight The sight shank is a steel arc which can be moved up and down in elevation by means of a scroll gear. A range strip on the rear face of the arc is graduated in 50-yard divisions up to the maximum range of the piece. Combined with the sight is a graduated level which serves the same purpose as the range quadrant used on the 3-inch equipment and other materiel of that type. By this means the piece is laid for elevation. The sight is mounted on the left side of the cradle. By having the quadrant level and sight thus combined one man can lay for both elevation and direction. The ammunition used is of the fixed type, consisting of steel high-explosive and shrapnel shells, each weighing 12J pounds. Each animal carries two chests containing five rounds each. COMPARATIVE TABLE OF LIGHT FIELD GUNS USED IN THE WORLD WAR. Austria, 1905. France, 1897. Ger- many, 1896 n/a Great Britain, 1917. Italy, 1912. Ru^ia. 1903. United States, 1902. United States, 1916. Caliber, inches 3.01 2.95 3.03 3.3 2.95 3. 3. 2.95 Weight of shrapnel, pounds 14.72 16.00 15.00 16.00 143 14.41 15.00 16.00 1,640 1,955 1,760 1,900 1,510 1,930 1,700 1,900 Muzzle energy, foot-tons 275 335 242 340 224 373 300 311 Weight of gun 700 1,000 766 995 690 785 835 749 Weight of gun and carriage . ... 2,000 2,650 1,860 2,890 2,260 2,075 2,520 3,045 Weight of gun caisson and limber Maximum elevation 3,750 18 4,150 19 4,200 16 4,420 16 3,350 65 3,850 4,490 15 4,556 53 Total traverse, degrees 8 6 8 8 52 5i 8 45 Length of recoil, inches . . . . '. 51.5 45 44 28-49 18-53 42.5 45 18-46 Diameter of wheels 4'3" 4'4J* 4'5J" 4'8" 4'3}" 4'4" 4'S" V8" Independent line of sight No. Yes No. Yes. Yes. No. No. Yes. Sight, goniometric, telescopic, pano- ramic, ordinary P. G. T. G. O. P. T. P. O. P. O. P. 0. P. Breech block, wedge swinging, eccen- tric screw W. E. S. W. S. W. S. B. S. B. W. Traverse, axle or pintle P. A. P. A. P. A. A. P. Recuperation, spring or hydropneu- matic 8. H. S. H. H. S. S. S. Length of gun, calibers 30 34.5 27.0 28.4 30 34 29.2 28.4 Width of track, inches 60 60 60 60 58 60 60 60 Range, maximum 6,400 9,350 7,600 8,100 8,850 7,800 8,500 12,500 75-MILLIMETER GUN MATERIEL, MODEL OF 1916. The United States 75 -millimeter field gun, model 1916, is of the split trail type, permitting greater traverse and greater elevation than either the French or British models of this caliber, equipped with the single trail. FRONT VIEW OF CARRIAGE. The 75-millimeter field gun constitutes the light field artillery of the Army. The caliber of the piece is about as large as ready horse- drawn mobility will permit. The caliber is equivalent to 2.95 inches, and was adopted by the French and by the Italians, while the United States had adopted the 3-inch caliber, and Great Britain a caliber of 3.3 inches which is the caliber of their 18-pounder. The German caliber was 77 millimeters, equivalent to 3.03 inches. The points of excellence obtained from these field pieces are : good range, rapidity of fire, ease of transportation, and reliable functioning. (69) 70 71 The American model 1916 split-trail carriage permits great eleva- tion, within the mechanism of the carriage, and likewise a wide traverse without changing the position of the trail. The recoil mech- anism was adapted to the higher permissible elevation of the gun. and equipped with a variable recoil, automatically adjustable for different elevation. The ability to outrange the enemy is constantly being sought, and high elevation and improvements of the projectile are the means through which it is hoped to obtain the increased range desired. Likewise, a wide horizontal arc of fire, without resetting of the trail and consequent resetting of the sighting devices, is a great convenience and saver of time. REAR VIEW OF CARRIA( As the range depends not only on the power of the gun and the design of the ammunition, but also on the elevation provided for, and as the horizontal arc which can be covered by a gun with a single setting of its trail is governed by the permissible traverse, attention is invited to the mechanical features covering the vertical and hori- zontal limits of the gun laying, as well as to the functioning of the piece. Of the above types, the French model has been credited with functioning most perfectly, but it lacks provision for high eleva- tion and wide traverse of the gun. Due to its greater elevation, the American piece outranges the French, although the French gun has a greater muzzle velocity. (See page 89.) Compared with the British model 1917, the American 3-inch model 1902 carriage permits of a maximum angle of elevation of 15, depression of 5, and traverse of 142 mils, while the British model permitted 16 elevation, 5 depression, and 142 mils traverse. The French model 1897 carriage permits a maximum angle of elevation of 19, depression 10, and traverse 106 mils. The American model 72 Ld O < cr cr > o in CD CD -J Ld n sU : t i 73 1916 carriage allows a total vertical movement of from 53 elevation to 7 depression and a traverse of 800 mils (an artillery mil equals the angle subtended by T * T of the circumference of a circle). The American model 1902 carriages are arranged with a hydro-spring recoil mechanism, and so is the British model 1917, and the Ameri- can model 1916. The French model 1897 carriage is equipped with a hydropneumatic recoil mechanism. The weight of the piece, including the carriage and limber, is about 4,500 pounds, which is slightly above the horse-drawn draft limitation over rough ground. The introduction of motor tractors may alter the draft problem, but there still remains the question of facility in handling the piece LEFT SIDE VIEW OF CARRIAGE. by man power after battery position has been reached. As one phase of this, it may be mentioned that the weight at the end of a 75- millimeter gun-carriage trail is only approximately 100 pounds. The trail can be readily unlimbered and spaded into position or its position changed by man power within a few moments, while to unlimber and spade into position, or to change position of the trail of a 155-millimeter gun requires the use of jacks and a considerable expenditure of time. Rapidity in moving a fieldpiece from point to point, where railroad transportation is not available, is not entirely a matter of the speed of the tractor, for likelihood of damage to the materiel when trans- ported at high speed on its own wheels must also be considered. The dimensions and weight of the 75-millimeter piece permit of its being placed on a rubber-tired trailer and transported at high speed behind a motor vehicle. The mobility of artillery is of utmost importance, and the 75- millimeter field gun has therefore become a gun of first rank, as it constitutes the light artillery of the military powers. This weapon 74 is accurate, has a range up to 7 miles, is suitable for the projection of high explosive, shrapnel, and gas projectiles, destruction of per- sonnel, of wire entanglements, and of fair-sized obstacles, and to some extent the destruction or protection of lines of communication. Weights, dimenaions, and ballistics. Weight of gun and breech mechanism pounds 749 Length of gun inches__ 90.9 Caliber millimeters.. ~~> Length of bore inches. _ 84 Length, calibers fS& 1 Rifling, right-hand twist ; increases from one turn in 119 calibers at the beginning of rifling to one turn in 25.4 calibers at a point 9.72 inches from muzzle. Uniform from this point to end of muzzle. Number of grooves 24 Muzzle velocity : Shrapnel Mark I (21-second combination fuze) feet per second __ 1,693 . Shell Mark IV (armed with Mark V fuze) ___ 1, 74'J Maximum range : Shrapnel (Mark I shell) yards.* 9,653 Shell (Mark IV) _ do 12,360 Shell (Mark I) _-_ do__ 8,780 Range at 10 elevation do__ ' 6,170 Range at 20 elevation do.. 9, 185 Range at 30 elevation do 11, 385 Weight of carriage, complete (without gun) pounds 2,280 Weight of gun and carriage, fully equipped do 3,045 Diameter of wheels inches 56 Width of track do 60 Length of recoil of gun on carriage (variable) do 18-46 Height of axis of gun above ground do 41.625 Weight at lunette, carriage limbered pounds 140 Height of center line of peep sight above ground inches 56.875 Height of center line of panoramic sight above ground do 52 Amount of elevation with elevating handwheel degrees 42 Over-all width of trails, spread inches.. 130 Over-all length, muzzle of gun to end of lunette do 173 Length, center line of wheel to center of lunette do 118. 28 Maximum angle of elevation degrees 53 Maximum angle of depression do 7 Maximum transverse, each side of center mils 400 Maximum angle of elevation with angle of site handwheel degrees 11 Maximum angle of depression with angle of site handwheel do 7 75-MILLIMETER GUN AND CARRIAGE, MODEL OF 1916. The gun is of the built-up construction and consists of a tube, jacket, locking hoop, breech hoop, and clip. There are six slightly varying types of this gun, but the variations deal only with the manner of attachment of the jacket and locking hoop and do not affect the general dimensions. The gun is guided in recoil by two flanges q|i the lower side of the jacket. A lug on top near the for- ward en$ of the jacket containing a T-slot holds the forward end of the recoil cylinder. A short hoop or clip is shrunk on the tube near the muzzle and has on its underside two lugs which form guides for the gun on the cradle. Provision has been made to prevent dust from entering be- tween the surfaces of the guides and their bearing surfaces on the cradle. The breech ring, which screws to the rear end of the jacket, forms a housing for the breech block which slides up and down with the action of a wedge. The ring carries at the top a lug to which the hydraulic recoil cylinder is secured, and at the bottom another to which the two spring piston rods are attached. The breech block is of the drop-block type and operates semi- automatically, in that the breech closes automatically when a round of ammunition is inserted. It is opened by pulling back a handle on the right side of the breech, which not only slides the breech block out of place but operates the extractor, thus ejecting the empty car- tridge case. When a round is inserted smartly into the breech, its rim strikes against the lips of the extractor causing the mechanism to close under the action of the closing spring. The cartridge primer is fired from the left side of the carriage by a continuous-pull firing mechanism. The firing pin is cocked and fired by one continuous backward motion of the firing handle. The carriage is of the split-trail type which means that the trail is made up of two halves, each being hinged to the axle near the wheels and capable of being spread out at a wide angle or brought together at the spade ends and locked for traveling. This feature permits greater elevation and traverse than the ordinary type of trail and reduces the necessity of shifting the trail when changes in deflection of 50 mils or more are desired. A seat is provided on each half of the trail, the one on the left for the gunner who operates the sights, the traversing and angle of site handwheels, and fires the piece, and the one on the right for a can- noneer who sets off the range and angle of site and operates the breech mechanism. (75) 77 The recoil mechanism is of the hydro-spring variable recoil type consisting of one hydraulic and two spring cylinders which comprise the recoil and counterrecoil mechanisms. On account of the high angles of elevation at which this gun can be fired, it was necessary to design a variable recoil system by means of which the length of recoil of the gun would be automatically lessened the higher the muzzle is elevated. This is accomplished by means of a valve turn- ing in the cylinder and shutting off or opening a number of holes,, proportional to the elevation, thus making the resistance to the passage of the oil greater or less. GUN AT MAXIMUM ELEVATION. The angle of site mechanism consists principally of a rocker which is moved by two handwheels, one on each side of the gun. Movement of the mechanism causes the gun, cradle, elevating mech- anism, and sights to move also, they being connected to the rocker. The handwheel on the left or gunner's side is used when laying for direct fire, or in other words, when site is set independent of range. The angle of site scale is graduated in mils. All settings on the angle of site scale are set off above or below the 300-mil graduation, this being the normal setting when the axis of the bore and the target are in the same horizontal plane. The elevating mechanism used in setting the range is mounted on the rocker, and therefore independent of the angle of site mech- anism, the gun and cradle only being moved upon operation of the handwheel. The range scale is graduated in meters. Band brakes are used on this carriage and are operated by a hand lever in rear of the shield when in b-^tterv position and by a lever from the axle seat when in traveling posiHon. 78 79 9 i In 5 *sl li ! M isl-fllf mi 5516021 6 80 INTERMEDIATE SHAFT GEAR - -5CEOWN NUr TRAVERSING 8TOR .C93<&X 1. 8755TEEL PIN.' TRAVERSING AZIMUTH SCALE: -ANCLE OF SITE BRACKET COVERCUTT) ^TRAVERSING HAMDWHEEL SHAFT. SRCXONti NUT. LW70DBOLT; ^^ANGLE OF SITE BRACKET(LFT) -StK HANDY OILER BOOV. isresra caiNK HEAD GERMAN SLVEI? SCREWSL INSTOUCTION PLATE (TRAVERSINGj.-^' CWkNK PIN. .625 CROWN NVT. -TRAVERSING WORM SHAFT BEARING. 1.812(1 $ STUD. -i CROWN NUT. TRAVERSING WORM SHAFT. TRAVERSING WORM (HINDLEY) I -TOP CARRIAGE. HALF BUSHINGi,T5VECraP CARRIAGE) .125 x .75 STEEL PIN.- 1 \ \ x ADJUSTING NUT. WASHERH ^-.125x1.75 SPLIT PIN. 75 M M.GUN CARRIAGE, MODEL OF 1916. TRAVERSING MECHANISM. 81 The gunner and cannoneers are protected by the customary shields and apron. The sight used is of the model of 1916 type, which provides a sup- port for the panoramic sight and the peep sight. ^Wooden wheels, 56 inches in diameter, with steel hubs and tires, are used, the tires being 3 inches in width. These wheels are interchange- able with those of the caissons and limbers. Fixed ammunition is used in the 75-millimeter field guns and is made up of either common shrapnel or common steel shell. Shrapnel rounds are issued with the projectiles filled and fuzed; the shell rounds are issued filled but not fuzed and contain an adapter with booster charge. The projectiles average in weight: Shrapnel, 16 pounds, fuzed; shell, 12.3 pounds, fuzed. The components of one round are the cartridge case with primer, powder charge, projectile, and fuze in shrapnel, and adapter and booster in the shell. Weight of powder charge is approximately 1.5 pounds. CARRIAGE AND LIMBER IN TRAVELING POSITION. A battery of 75-millimeter gun carriages, model of 1916, is accom- panied by the following vehicles: 75-millimeter gun carriage limber, model of 1918. 75-millimeter gun caisson, model of 1918. 75-millimeter gun caisson limber, model of 1918. Forge limber, model of 1902 MI. Store limber, model of 1902 MI. Battery and store wagon, model of 1917. Battery reel, model of 1917. 1 Feel, model of 1909 MI. Cart, model of 1918. 1 The above gun carriage was originally the 3-inch gun carriage T model of 1913, which was later called the 3-inch gun carriage, model of 1916. The gun was afterwards modified to caliber 75 millimeters, as was the 3.3-inch British, thereby permitting interchangeability of ammunition with the French guns. 1 For horse batteries the battery reel, model of 1917, is issued. For motorized batteries the reel, model of 1909 MI, with the cart, model of 1918, is issued in lieu of the battery reel, model of 1917. 82 75-MILLIMETER GUN MATERIEL, MODEL OF 1916 MI. A number of 75-millimeter gun carriages, model 1916, redesigned to use St. diamond hydropneumatic recoil mechanisms in place of th& hydrospring type, and standard 75-millimeter guns, model of 1916 Mill, modified and fitted with counter weights, are available for issue to the service. The new materiel will be known as 75-milli- meter gun materiel, model of 1916 MI. LEFT SIDE VIEW OF CARRIAGE IN FIRING POSITION. The St. diamond mechanism as adopted for the 75-millimeter carriages is of the hydropneumatic type and was developed in 1917 by Col. Rimailho, of the French Army. The use of small forg- ings was made possible by introducing high pressures in the recuper- ator and recoil cylinders. In order to hold these pressures, special suitable packings had to be used. Essentially the mechanism consists of three cylinders. The middle one is the recoil cylinder. The right cylinder has an air reservoir at its forward end and an oil reservoir at the rear end. The left cylinder is the recuperator cylinder, having at its forward end an air space, and at its rear end a regulator for controlling the length of recoil. The floating piston in this cylinder separates the air from the oil. In recoil the gun moves to the rear, carrying with it the recoil piston (middle cylinder). The recoiling parts are held in battery by the reaction of the air on the floating piston, which is transmitted through the liquid against the leak-tight recoil piston. The energy of recoil is absorbed by the throttling of the oil through a spring-controlled orifice in the regulator valve. (83) 84 85 An opening is provided between the recoil and the recuperator cylinders to house the regulator valve. During recoil the pressure in the recoil cylinder opens the regulator valve, the movement of which is controlled by a helical spring and a number of Belleville springs. The oil passing through the orifice controlled by this valve moves the floating piston forward against the air pressure, thereby storing up energy to return the gun from the recoiled position to its position in battery. The valve in the counterrecoil orifice remains closed during recoil. Throttling during recoil is controlled by the regulator valve con- sisting of an upper and lower valve stem. The lower valve stem is seated in a circular seat at the entrance channel to the valve. As the valve lifts, the throttle area becomes the vertical circumferential RIGHT SIDE VIEW OF CARRIAGE IN BATTERY POSITION. area between the valve and its seat. In long recoil the movement of the valve is controlled by a spiral spring which reacts on the lower valve stem. The upper stem rests in a valve housing and has Belle- ville springs reacting on the stem only. To move the upper valve stem, the whole housing is lowered automatically by a cam operated when the cradle is elevated. At short recoil the upper stem of this regulator is brought down by the cam until its lower surface is in contact with the top surface of the lower valve stem, thus controlling the throttling of the valve. The regulator valve is closed during the counterrecoil movement except for a very small constant opening. During counterrecoil there is also a second path for the flow of oil through a small channel beginning at the inside end of the buffer chamber in the recuperator cylinder and finally emptying in the recoil cylinder through a by-pass around the regulator valve. Near the end of counterrecoil the taper- 86 ing buffer rod on the floating piston in the recuperator controls the flow through the second path by causing additional throttling through the small annular arc between the buffer chamber and buffer rod, thus bringing the recoiling parts to rest without any great amount of shock. 75-MILLIMETER GUN MATERIEL, MODEL OF 1897 MI. (FRENCH). The French 75-millimeter field gun adopted for the service of the United States dates back to 1897, when it was perfected by the French Army. The French model 1897 field gun has fired, on test, as high as 30 shots in a minute. This rate is probably as high as can be reached by any nonautomatic 75 gun. Apart from the personnel service to the piece, the length of time which a gun could maintain this rate of fire, or any other rapid rate of fire, is perhaps not definitely de- termined. As to whether or not such length of time would be limited by the heating of the gun or by the heating of the recoil mechanism depends upon the construction. Rapidity of fire is of vital importance, for it is self-evident that under certain conditions a gun which can fire twice as many shots per minute as some other gun is, for the moment, equivalent to two guns of the second class. Rapidity of firing action is dependent upon the arrangements involved for the sighting, maintaining of the gun on its range, loading, firing, time of recoil and return of the gun to battery position, opening of the breech, and ejection of the empty cartridge case. For artillery of position a great part of the enormous energy re- quired to start the projectile on its way may be absorbed by a heavy foundation furnished as a mounting for the piece. An efficient recoil mechanism is, however, of vital importance in connection with light artillery for field service, owing to the essentially light weight of the carriage on which the gun is mounted, to permit of its ready mobility. The recoil mechanism not only absorbs the greater part of the recoil energy of the gun but it returns the gun to the battery or firing position, and to be efficient it must be able to perform these two functions quickly, smoothly, surely, and continuously. The w r ord "surely" is used in the sense of firmly and without shock, and of being reliable. The recoil mechanism not only takes up the recoil but it forces the gun all the way back into battery, or to a position within the variation which the design permits, under all conditions of elevation and heating. (87) 88 89 The general theory of hydropneumatic recoil mechanism is not new. In its relation to light artillery its most notable exemplification in battle has appeared in the Puteaux Arsenal type used with the French 75 piece. Its virtues have been widely heralded and every effort has been made to keep its construction secret. Its several parts were manufactured at different points in France and these were assembled in a central establishment, where but few persons were admitted to this room. In the agreement to manufacture the complete recuperator in the United States, it was stipulated that the greatest secrecy should be maintained with reference to its design, manufacture, and assembly. There is a difference between land and naval warfare, in this respect: In a duel between two large fighting ships of equal speed to insure their remaining in contact, the one with the heavy, long- range guns has the other at its mercy, as it can destroy both its oppo- nent's base and at the same time its opponent's personnel by sinking the opponent ship. In a land battle, the fortifications may be reduced by the long-range gun, of heavy caliber, but it is the destruction or capture of personnel which brings a war to an issue and the personnel may move to open country and open order, under which conditions the heavy, long-range gun, which is expensive to construct, slow and difficult to transport, expensive to fire, and withal short of life, no longer has a great target on which its tremendous energy may be concentrated. Land warfare has clearly demonstrated that it is the killing and disabling of personnel or the capture of enemy troops in large num- bers which far outweighs the capture of cities or of terrain which is nonproductive of raw material, in the forcing of an issue. This To-millimeter gun was most effective in the open-country fighting, in the protection of troops, and in working havoc among enemy troops and bringing in prisoners by creeping barrage laid behind an enemy formation. Weights, dimensions, and ballistics. Caliber millimeters 75 Total weight of gun and breech mechanism pounds 1, 015 Total length of gun inches 107,125 Rifling, uniform, right hand, 1 turn in 25.6 calibers. Muzzle velocity : Shell (short fuze) feet per second 1,955 Shell (long fuze) do 1,930 Shrapnel do 1, 755 Maximum range: Shell (short fuze) (Mark IV shell) yards 8,640 Shell (long fuze) do 9,350 Shrapnel do 7, .440 90 91 Weight of complete round of ammunition : Shrapnel pounds 16 Shell . do 12. 3 Diameter of steel tired wheels inches 52. 5 Width of track do 59. 68 Length of recoil of gun on carriage do 44. 9 Height of axis of gun from ground do 40. 4 Maximum angle of elevation degrees 19 Maximum angle of depression do 10 Total traverse of carriage on axle do 6 Weight of the carriage, complete (without gun) pounds__ 1,642 Weight of gun and carriage, fully equipped 2,657 75-MILLIMETER GUN AND CARRIAGE, MODEL OF 1897 MI (FRENCH). The gun is of the built-up construction type, consisting mainly of a steel tube reinforced at the breech end with a breech hoop and covered in the central portion with a bronze jacket. The total length from face of breech to muzzle is slightly less than nine feet. The recoil lug under the breech carries the coupling key, which connects the gun to the recoil mechanism. A safety pin operates between the breechblock and the coupling key, so that it is impossible to close the breech and fire the gun when it is not securely locked to the recoil mechanism of the carriage. On the underside of the gun are inclined bronze slides which are in contact with similar slides on the recoil mechanism. Rollers are also attached to the gun, and during recoil the gun first slides on the inclined guides and then the rollers lift the weight off the slides, the remainder of the travel being on the rollers. A pair of rollers at the muzzle permit a long recoil with short guides by taking the overhanging weight when the gun is at full recoil. The breechblock is of the Xordenfeld type, cylindrical in shape and threaded on the outside. It is opened or closed by the operating handle from the right side of the gun by the same man who sets the gun for range and fires the piece. Opening the breech automatically actuates the extractor, which in turn ejects the empty cartridge case. The round of ammunition is fired by a striker which is driven for- ward by a spring-actuated hammer pulled by the lanyard. The carriage is very compact and simple, consisting of a housing around the axle, above which is the support for the cradle, and a box section trail ending with the customary spade and lunette. Seats are provided for two men, the one sitting on the right side operating the range scale mechanism, opening or closing the breech and firing the piece ; the man on the left sighting the gun and oper- ating the angle of site and traversing mechanisms. The recoil mechanism is of the hydropneumatic, long recoil type and contains both recoil and counterrecoil mechanisms. A gage 92 93 94 plunger is located in the rear end of the cradle which, when flush, indicates that more oil should be added until the plunger projects about f inch. Oil may l?e added by forcing it through a valve in the side of the cradle by a hand screw filler, or by means of a portable battery pump clamped to the side of the trail and connected through the trunnions to the interior of the cradle. The recoil mechanism is housed inside of the cradle, through which are bored an upper and lower cylinder, filled with Oleonapthe, and connected together by means of a passageway provided for that purpose. The air in the front part of the upper cylinder (in front of the piston) is free to communicate with the outside air through a plug, but the forward end of the lower cylinder is closed and con- LEFT SIDE VIEW OF CARRIAGE. tains compressed air at approximately 150 kilograms per square centimeter (1,833.5 pounds per square inch). In the upper cylinder a piston is permitted to move, the piston rod, however, being secured to the gun. The lower cylinder is fitted with a pipe, at the end of which is a circular ring, this pipe being screwed in the rear part of the cylinder where the valves are housed. A diaphragm equipped with a hollow rod, also a floating piston fitted with a small rod, are incorporated in the lower cylinder. During recoil the piston of the upper cylinder compresses the liquid, forcing it to pass through various valves, also openings formed between the pipe and the hollow rod of the diaphragm. The passing of the liquid through these different openings constitutes the braking. In so moving, the liquid opens the valves (which are opened 95 551 GO 21 7 97 wide at the beginning of the recoil and gradually close in propor- tion to the decrease of the speed of the recoil). At the same time, the air in the lower cylinder is compressed by the action of the liquid on- the diaphragm. To return to battery at the end of the recoil, the compressed air forces the diaphragm back. The liquid thus compressed acts directly on the upper cylinder piston, causing it to return to its initial position. The interior of the recoil mechanism was maintained confidential by the French Government before and during the war, and when its manufacture was taken over by the Ordnance Department, agree- ment was made to continue the secrecy of these parts. Very fine adjustments are made when the parts are assembled, and conse- quently no repairs or adjustments are permitted to be made in the field. The complete recoil mechanism must be sent to special repair depots for repairs. The recoil mechanism will function properly without the operating personnel understanding the interior mech- anism. The angle of site mechanism consists of a handwheel and gears, and provides for elevating or depressing a rocker 13 degrees with reference to the trail. The rocker fits around the trunnions and has a segment of a gear which meshes with the elevating pinion. To the rocker is secured an elevating screw and nut which connects with the cradle. In setting the angle of site, the rocker is set in motion, thereby moving the cradle and gun. The angle of site mecha- nism is also called the independent line of sight; because the range setting is independent of the setting of the angle of site which is done by the angle of site handwheel. The range scale mechanism which operates the elevating screw provides an elevation of 12 degrees to give the correct range and is obtained by movement of the cradle in reference to the rocker. The circular scale graduated in meters indicating the range is mounted on the side of the cradle and through gearing is connected to the elevating screw. A range rack is connected to the rocker arm which is also graduated in meters. On carriages made in America an extra strip is placed alongside the range rack and is graduated in mils. The range scales are graduated up to 5,500 meters, but greater ranges can be obtained by burying the trail, and thus giving higher angles of elevation. Interference of the breech against the trail, however, limits the total possible elevation obtainable by combination of the elevation due to the angle of site and that due to range to 19 degrees. On this carriage axle traverse is used. A geared nut, held inside of the axle housing, rotates around the axle which is threaded with a coarse rectangular thread. Movement of this nut forces the 98 carriage to the right or left, pivoting around the spade, one wheel advancing and the other backing up. Traverse is about three degrees right and three degrees left. A combination road brake and firing support is hung around the axle, permitting the application of brake shoes against the tires of the wheels when traveling, and the lowering of the framework to & u A S_ , c M t&llftjl >-. -O :>-2feS J= S-S t'3 C 3 s , ^^^ 1*11 i. ft ^--' ^ o -j- 1'- r - o O ^ ^ i^ ?: M [ ^ ri ^ o x c O 75-MILLIMETER GUN CARRIAGE LIMBER, MODEL OF 1917 (BRITISH). The standard British limber carries cartridges horizontally, but is not arranged with compartments or diaphragms. The American product of the British limber is superior to the standard British vehicle in that diaphragms are included in the ammunition chests. The limbers are fitted with wooden poles, which are more liable to breakage than steel poles; they have single draft hooks, in- stead of double trees for equalizing the pull on the braces ; the pin- tle latch is not so effective as the American, nor the ammunition chest doors so well suited to their purpose; and they are not adapted to the American harness, as the distance from the neck yoke to the draft hook is 6 inches shorter than in the American design and our harness can not be so readily connected to the neck yoke. FRONT VIEW OF LIMBER. Weights, dimensions, etc. Weight, complete, empty pounds 1,016 Weight of tools and equipment carried do 114 Weight of ammunition carried do 516 Weight, completely equipped and loaded do 1, 646 Weight of gun, carriage and limber, completely equipped with 21 rounds of ammunition pounds 4, 591 Diameter of wheels inches,- 56 Width of track do 60 Turning angle with carriage degrees-- 70 The British design of gun carriage limber is constructed of a frame consisting of two middle and two outer rails connected at the front and center by a bar and braces and surmounted by an ammunition chest of steel. (116) 116 1 I K 1 E I i 117 I 1 Sv, I I 118 The chest opens at the rear and is fitted with perforated diaphragms for carrying 24 rounds of fixed ammunition and a compartment in the center holding two wooden trays for small stores. The pole is of wood, protected at the front end by steel wrapping plates and fitted with a neck yoke for use with breast collar harness. REAR VIEW OF LIMBER. The axle is a seamless steel tube fixed to the rails by flanges, and the wheels are the same as those used on the gun carriage. This limber is used only in connection with the 75-millimeter gun carriage, model of 1917 (British). The 75-millimeter gun carriage limber, model of 1918 (American) a description of which may be found on page 119, can be used as an alternate for this vehicle. 75-MILLIMETER GUN CARRIAGE LIMBER, MODEL OF 1918. The limber is of American design, and is of metal throughout, excepting the spokes and felloes of the wheels. The frame consists of a middle rail and two side rails. The middle rail is in the form of a split cylinder, one half passing below and the other half above the axle, uniting in front to form a seat for the pole and in the rear to form a seat for the pintle-bearing guide. An automatic pole support, described on page 169, is provided. The ammunition chest is a rectangular steel box, having a door at the rear hinged at the bottom, and swinging downward to an approx- imately horizontal position. Three perforated diaphragms within the chest support 18 rounds of fixed ammunition and 3 tubular oil cans. The axle is of forged steel, made in one piece. The standard 56-inch wheels are used. (See page 167.) This limber is used in connection with American, British, and French 75-millimeter materiel. Weights, dimensions, etc. Weight complete, empty pounds 963 Weight of tools and equipment carried, oil cans filled do 134 Weight of ammunition carried (shrapnel) do 365 Weight of fuze boxes, loaded do 62 Weight, completely equipped and loaded do 1, 524 Rounds of ammunition carried in limber chest 18 Diameter of wheels inches 56 Width of track do 60 Free height under limber do 24 Turning angle with carriage degrees 78 (119) 120 REAR VIEW OF LIMBER. FRONT VIEW OF LIMBER. 121 122 > i i , yiPiii i njr ill! Ill i iifii&JiSliiliiif' FT/A i-/ ---- 1 ! > W- iililiili 75-MILLIMETER GUN CAISSON, MODEL OF 1918. The caisson consists of a steel chest carried on wheels and axle by means of a spring support. This support consists of helical springs held by suitable axle and chest brackets at each end of the chest. The Belleville springs absorb the shock of rebound. FRONT VIEW OF CAISSON. The chest carries 70 rounds of ammunition arranged in 5 horizontal rows of 14 each. Protection from small-arms fire is provided by the front door, rear plate, and apron, which are made of armor plate. The chest provides seats for three cannoneers, and is equipped with fastenings for carrying a full complement of tools. A rack is pro- vided at the back of the chest for carrying fuze boxes. On the front left side of the chest is fastened the fuze setter. The caisson is equipped with a short pole and lunette combined with a pole prop. On the rear the standard pintle is provided. (123) 124 Standard 56- inch wheels are used and band brakes are provided. (See page 167.) GUN CAISSON AND GUN-CAISSON LIMBER, LIMBERED. Weights, dimensions, etc. Weight, complete, empty pounds 1,425 Weight of tools and equipment carried do 62 Weight of ammunition carried (shrapnel) do 1,421 Weight of fuze boxes, loaded do 124 Weight, completely equipped and loaded do 3, 032 Weight with limber completely equipped and with 106 rounds of ammuni- tion pounds 4,961 Rounds of ammunition carried 70 Diameter of wheels inches 56 Width of track do 60 Free height under caisson do 81 Turning angle with limber degrees 81 75-MILLIMETER GUN CAISSON LIMBER, MODEL OF 1918. The gun caisson limber is practically the same as the gun carriage limber, model of 1918, except that the chest is larger and carries more ammunition. Each diaphragm is perforated with 39 flanged holes, which accommodate 36 rounds of ammunition, and three tubular oil cans. This limber is used in connection with the American, British, and French 75-millimeter materiel. FRONT VIEW OF CAISSON LIMBER. Weights, dimensions, etc. Weight, complete, empty pounds 1,003* Weight of tools and equipment carried (oil cans filled) do 134 Weight of ammunition carried (shrapnel) do 730 Weight of fuze boxes, loaded do 62 Weight, completely equipped and loaded do 1,929 Rounds of ammunition carried in limber chest 36 Diameter of wheels : inches 56 Width of track do 60 Free height under limber do 24 Turning angle with caisson degrees 81 (125) 126 3-INCH GUN MATERIEL, MODEL OF 1902. When the United States entered the World War there were on hand approximately 544 3-inch field guns, model 1902, and the neces- sary equipment therefor. The 3-inch, model 1902, materiel includes gun, carriage, limber, caissons, caisson limbers, battery wagons, forge limbers, store wagons, store limbers, combination battery, store wagons and limbers, battery reel, also reel and carts, as issued to the 75-millimeter materiel. The needs of the fighting army received first attention, but a large number of troops in the training areas and camps required materiel for use in their preliminary instructions; thus 154 batteries of 3-inch, model 1902, materiel were distributed for training purposes in the United States which were considered substitutes for the 75-millimeter materiel. The 3-inch field gun, American model 1902-1904-1905, is equipped with a breechblock of the interrupted-screw type. The breech mecha- nism consists of a handle pivoted vertically to provide horizontal movement of the handle to the right to open the breechblock. In opening, the mechanism performs two functions: Revolves the breechblock, releasing it from the threads, and then swings the block open. At the same time the cartridge case is ejected from the gun. In closing, the threaded movement firmly seats the cartridge in the powder chamber, and the threads withstand the backward thrust of the powder gases. The recoil mechanism is of the hydro-spring type, with the housing attached to the carriage, and located underneath the cannon. The firing mechanism, in the latest design, is operated either by a lanyard attached to the trigger, or by means of a firing handle on the cradle, and is of the continuous-pull type. When the breechblock is unlocked the gun can not be fired. Weights, dimensions, and ballistics. Weight of gun : Models of 1902 and 1904 pounds 835 Model of 1905 do 788 Caliber inches__ 3 Length of gun do 87. 8 Length of bore do 84 Length of rifled portion of bore do 72. 72 5516021 9 (127) 128 FRONT VIEW OF CARRIAGE. REAR VIEW OF CARRIAGE. (129) 130 Rifling : Number of grooves 24 Width of grooves inch__ 0. 2927 Depth of grooves do 0. 03 Width of lands do 0. 01 Twist, right-hand : Models of 1902 and 1904 ; 1 turn in 50 calibers at origin to 1 turn in 25 calibers at 12.52 inches from muzzle, thence uniform. Model of 1902 : turn at origin to 1 turn in 25 calibers at 9.72 inches from muzzle, thence uniform. \Veight of projectile (filled and fuzed) pounds 15 W T eight of cartridge case_. do 2. 2.~i Weight of fix^d ammunition (1 round) do is. ir, Capacity of cartridge case cubic inches 66. 5 Muzzle velocity feet per sec__ 1, 700 Maximum pressure per square inch pounds__ 33,000 Range at 15 elevation yards__ 6,000 Maximum range (approximately) do 8,500 Weight of carriage, with 4 rounds of ammunition weighing 75 pounds, pounds 1,685 Weight of gun and carriage, fully equipped pound* 2,520 Weight at end of trail, carriage limbered do 115 Diameter of wheels inches 56 Width of track do 60 Length of recoil of gun on carriage do 45 Height of axis of gun do 40. 875 Height of line of peep sight do 44. 9 Length of peep-sight radius do 36. 75 Maximum angle of elevation degrees !"> Maximum angle of depression do 5 Amount of traverse of gun and carriage 1 mils 140 Rounds of ammunition carried on carriage 4 3-INCH GUNS, MODELS OF 1902, 1904, AND 1905, AND CARRIAGE, MODEL OF 1902. The guns are of three models, 1902, 1904, and 1905, and are prac- tically the same except that the latter two models differ from the 3902 model in breech mechanism and the 1905 model is 50 pounds lighter in weight. The gim is built up of nickel steel and consists of a tube, the rear portion of which is enveloped by a jacket which also projects beyond the rear end forming a recess for the breechblock. A locking hoop is shrunk on the tube and the forward end of the jacket to secure the latter to the tube. The front clip is a short hoop shrunk on the tube near the forward end which guides the gun in recoil. The breechblock on all three models is of the interrupted-screw type, and rotates in. the block carrier which is hinged to the rear end of the tube on the right side. The block of the 1902 model has two threaded and two slotted sectors and the block of the 1904 and 1905 models, which have identical breech mechanisms, has four (131) iltw 5 S^ 1 IP *4& , *; vi ^ S^'s^t'S ti^ "^"^fc ' ^"^ llf3f?44S*3JrtWllI Sac^^lcat^^Nsss^fc'S^ t^**^t??tt ; - 5; b*** ^l-| s>^ i ^ ^t ^ iS^^'^'Gt^'i^l'^ ^ ** -^ xi: (132) 133 threaded and four slotted sectors. The breechblock is operated by a lever pivoted to a lug on the block carrier which has at its outer end a handle and at its pivot end, a segment of a bevel gear, meshing with a corresponding segment on the rear face of the block. On pulling the handle to the right, the first 117 rotates the block until the threaded sectors are disengaged. A further movement of 90 swings the block and carrier on its hinge until free of the bore. The firing pin is eccentrically located in a recess in the block, when the breech is open. As the breech is closed the pin. is automat- ically moved to one side until it is in alignment with the axis of the bore and primer of the cartridge case. This is a safety feature which prevents the accidental discharge of a round before the breech has been fully closed. The carriage is known as model of 1902. A tapering box-shaped trail is secured to brackets around the axle and has at its rear end a spade and float. Two compartments are provided in the trail, one for tools and one for the rear sight. A seat is riveted to each side of the trail, one on the left for the gunner, and one on the right for a cannoneer. In front of the compartments are two cross transoms which form a support for the elevating mechanism. The cradle has riveted to its underside a pintle which seats in a pintle socket secured to the axle, by means of which the cradle and gun is rotated. The top and main shield and an apron are provided for the pro- tection of the personnel from gun fire. The recoil mechanism is of the hydrospring type. The recoil cylinder is fastened to the gun lug and therefore recoils with the gun. The piston, rod, being secured to the cradle head, remains stationary during recoil. Throttling during recoil is obtained by the use of three throttling bars, on the interior of the recoil cylinder, the piston having three slots cut in it to correspond to the throttling bars. During recoil the piston is stationary and the hydroline oil in the cylinder is forced past the piston through the slots. As the throttling bars, due to their increasing size, gradually close the slots in the piston, the gun is gradually brought to a stop. The counterrecoil mechanism consists of three nests of inner and outer springs which function to return the gun to battery and serve to partially check the recoil. The counterrecoil buffer consists of a tapered rod secured in the end of the cylinder which enters the hollow end of the piston rod, displacing the oil therein and preventing shock when the gun returns to battery. The elevating mechanism is of the double-screw type, consisting of a screw pivoted to the rear end of the rocker, which is moved up or down by the rotation of a bevel gear threaded on its interior surface. This bevel gear is rotated by a bevel pinion operated by a crank handle on either side of the trail. 135 Traversing is accomplished by means of a traversing shaft oper- ated by a handwheel on the left side of the carriage. This shaft is threaded and passes through a nut which is pivoted to the cradle. The nut being secured to prevent its turning, swings the cradle in traverse, when the traversing mechanism is operated. A lock is provided for locking the cradle to the trail in order to relieve the elevating and traversing mechanisms of any unnecessary strains during traveling. CARRIAGE AND LIMBER HAULED BY TRACTOR. Seats are supported on the axle on each side of carriage in front of the shield for the cannoneers, when traveling. Foot rests are pro- vided which also support the brake levers and ammunition carriers, there being four of the latter which make it possible to open fire quickly if necessary. CARRIAGE AND LIMBER IN TRAVELING POSITION. The brakes are of the shoe type and may be operated from either in front or rear of the shield, in the former case when traveling, and in the latter case when in firing position. Standard 56-inch wheels are used. (See page 167.) The instruments provided for sighting and laying the piece include line sights, a rear sight, a front sight, a panoramic sight, and a range quadrant. Three kinds of fixed ammunition are used in the 3-inch gun, models of 1902, 1904, and 1905, namely, common steel shell, common 136 137 138 shrapnel, and high explosive shrapnel. Each round is issued with projectiles filled and fuzed. The weight of the projectile is 15 pounds and the total weight of one round is 18.75 pounds. 3-INCH GUN MATERIEL, MODEL OF 1902. This materiel includes the following: 3-inch field gun, model of 1902, 1904, or 1905, mounted on car- riage, model of 1902. 3-inch gun limber, model of 1902 and 1916. 3-inch gun caisson, model of 1902 and 1916. Forge limber, model of 1902 and 1902 Ml. Battery wagon, model of 1902, 1902 Ml and 1917. Store limber, model of 1902 and 1902 Ml. Store wagon, model of 1902, 1902 Ml and 1917. Battery reel, model of 1917. The above materiel is entirely of American design and manu- facture. 3-INCH GUN LIMBER, MODEL OF 1902. The limber, excepting the spokes and felloes of the wheels, is of metal throughout. The principal parts are the wheels, axle, frame, ammunition chest, pole, doubletree, singletrees, and neck yoke. The wheels and wheel fastenings are the same as, and interchange- able with, those used on the carriage. The axle is hollow, of a single piece of forged steel, the axle body being provided with lugs, to which the middle and side rails of the frame are riveted. The side rails are of channel shape, divided at the front, one branch being led forward and secured to the middle rail near the pole seat, REAR VIEW OF LIMBER. while the other branch is utilized as a foot-rest support. The foot rest is a perforated steel plate formed to shape and riveted to the middle and side rails in front of the ammunition chest. The rear ends of the side rails project slightly beyond the chest to form steps for the use of the cannoneers in mounting. The frame consists of a middle and two side rails riveted to the axle lugs. The middle rail is in the form of a split cylinder, one-half passing below and the other half above the axle, which are joined in front to form a seat for the pole and in rear to form a seat for the pintle bearing. The pintle bearing is of bronze, made in halves and bored out to take the pintle shank. The pintle has a swiveling motion of 360 upon its shank, but is kept in its normal position by the spring in the bearing. The doubletrees and singletrees are formed of flange steel. Two doubletree rods each from the ends of the doubletree to the tie-rod clamps on the axle to which they are pinned. A pole prop is hinged (139) 140 to the rear end of the pole and when not in use it is secured by fasten- ings under the limber frame and the prop-chain button on the foot rest. The ammunition chest is a rectangular steel box built up of sheet steel and riveted together. The chest door is hinged at the bottom and swings downward and to the rear to an approximately horizontal position, where it is held by two door chains, and is held in its closed position by a shot bolt at each of the upper corners and by a lock in the middle. Inside of the chest the cartridges are supported by three vertical diaphragms, flanged all around and riveted to the body of the chest. Each of the diaphragms is perforated with 39 flanged holes. Corre- sponding holes in the middle and rear diaphragms are connected by conical brass tubes, which are cut away on top to reduce weight. These connecting pieces support the front end of the cartridge case and enable empty cases to be carried. The rear end of the connecting piece is turned over the rear face of the flange of the perforation in the rear diaphragm, and forms a stop for the rim of the cartridge case. The chest door closes against the head of the case so that the cartridge is firmly held in position. Suitable finger clearances are cut in the flange of each cartridge hole in the rear diaphragm to enable the fingers to get a good hold on the rim of the case in with- drawing it from the chest. Seats for three cannoneers are provided and the paulin issued with each limber serves as a seat cushion. Watering buckets are carried in suitable compartments provided for them between the seats and the chest. At each end of the seat is a handrail which projects above the top of the chest. At the front a lantern and two picket ropes are carried. Brackets for carrying an ax, a shovel, and pole prop are provided under the limber. All of the implements are secured in their brackets by leather straps, and held by strap fasteners provided for that purpose. With each limber are issued three oil cans, each of the general form of a cartridge and of a capacity of approximately two-thirds of a gallon. They are intended for hydro- line, lubricating, and coal oil, and are to be carried inside the chest in the central vertical row of cartridge holes. Weights, dimensions, etc. Weight, complete, empty pounds__ 964 Weight of tools and equipment carried do 101 W T eight of ammunition carried do 675 Weight, completely equipped and loaded do 1, 740 Rounds of ammunition carried in limber chest 36 Diameter of wheels inches 56 Width of track do 60 Free height under limber do* 22 Turning angle with carriage degreos__ 80 Turning angle with caisson do 75 3-INCH GUN CAISSON, MODEL OF 1902. This caisson, with the exception of the spokes and felloes of the wheels, is of metal throughout. The frame is diamond-shaped and composed of two channel section side rails riveted to lugs on the axle and meeting in front and rear at the lunette and pintle, respectively. FRONT VIEW OF CAISSON. The ammunition chest is a rectangular steel box of flange steel containing three vertical diaphragms which support 70 rounds of ammunition. Caissons having serial numbers 1141 to 1284, inclusive, have provisions for but 56 rounds. The door of the chest is in the rear and hinged at the top, the door opening upward and held at each end by a prop. An apron of armor plate is hinged under the axle and may be secured in a horizontal position for traveling. A fuze-setter bracket is pivoted to the apron hinges on the right side of the carriage at the rear. It is raised and secured for traveling. The road brake is designed similar to that of the gun carriage, with all parts as far as possible being interchangeable. The standard 56-inch wheels are used. (141) 142 Weight, dimensions, etc. Weight, empty pounds.. 1, 424 Weight of tools and equipment carried do 84 Weight of ammunition carried do 1,312.5 Weight, completely loaded and equipped do 2,820 Rounds of ammunition carried 70 Diameter of wheels inches 56 Width of track do 60 Free height under caisson__ do 22. 5 Turning angle degrees 75 3-INCH GUN CAISSON, MODEL OF 1916. The frame consists of two side rails and a middle rail braced by tie-rods, and by the ammunition chest to which they are rivited. The chest is a rectangular flange steel box containing three ver- tical diaphragms supporting TO rounds of ammunition. The door is hinged to the front of the chest, swings upward on its hinges, and is held by a door prop on the left side. An apron of armor plate is hinged below the chest for the protec- tion of the personnel. FRONT VIEW. SHOWING DOOR SWUNG UPWARD EXPOSING AMMUNITION. Band brakes are used similar to those on the 75-mm. gun car- riage, model of 1916, several parts of which are interchangeable. Brakes are applied by a hand lever on the right side, operated by one of the cannoneers seated on the chest. Weights, dimensions, etc. Overall length (traction pole removed) inches__ * 64 Overall width do * 74 Overall height do * 57 Weight, empty pounds 1, 384 Weight of tools and equipment carried do 53.5 Weight of ammunition carried do 1,312.5 Weight, completely equipped and loaded do 2, 750 Rounds of ammunition carried do 70 Diameter of wheels inches 56 Width of track do 60 Free height under caisson do 21 Turning angle degrees-- 81 Approximately. 5516021 10 ( 1 43 ) 144 to S3 b _j 145 3-INCH GUN LIMBER, MODEL OF 1916. With the exception of the chest, the limber is the same as the 75-millimeter gun caisson limber, model of 1918. The main differ- ence in the chest is in the size of the holes in the diaphragms, which are larger to accommodate 3-inch ammunition. Weights, dimensions, etc. Overall length inches * 120 Overall width do * 74 Overall height do * 63 Weight, complete, empty pounds 987 Weight of tools and equipment carried (oil cans filled) do 113 Weight of ammunition carried do 675 Weight, completely equipped and loaded do 1,775 Rounds of ammunition carried in limber chest do 36 Diameter of wheels inches 56 Width of track do 60 Free height under limber do 24 Turning angles with carriage degrees 80 Turning angle with caisson do 81 Approximately. 146 CO CD Q O CC 51 BATTERY WAGON, MODEL OF 1902. The frame consists of two side rails joined at the front to form a seat for the lunette bracket and projecting directly to the rear beyond the axle. A forge vise is securely fastened to the left side of the frame in place of the handle. REAR VIEW OF BATTERY WAGON. The chest is of wood and is bolted to the side rails. The interior is divided into four compartments; the largest being accessible through a hinged lid at either end of the top. The other three com- partments are in the lower rear portion of the chest, and are entered by a door at the rear end which opens downward. Of the three compartments, the right one is for the saddler's chest; the left one for the carpenter's chest, and the middle one for the cleaning mate- rials and small stores chest. In the larger compartment is carried the grindstone and frame, the jackscrew, and the packing chest containing spare breech mechanism. A chest for spare sights is furnished, which may be carried either in the battery or store wagon. (147) 148 In rear of the axle and under the chest are carried three oil cans of 5 gallons capacity each. Fastenings are provided on either side of the chest for carrying the two spare wheels. The wheels used and carried are standard 56-inch. (See page 167.) This battery wagon is used only in connection with the 3-inch gun materiel, model of 1902. Weights, dimensions, etc. Weight of battery wagon, empty pounds 1, 244 Weight of battery wagon, completely equipped and loaded do 2,747 Diameter of wheels inches 56 Width of track do 60 Free height under wagon do 26 Turning angle degrees-- 7.1 BATTERY WAGON, MODEL OF 1902 MI. The battery wagon, model of 1902 MI, differs from the model of 1902 in the following respects: The chest with attachments is stronger, better braced, and at- tached in a better manner to the frame. The weight of the spare wheels is carried directly by the axle instead of at the top of the chest. The parts of the chest are bolted and screwed together so that they may be readily disassembled if necessary. The corners are not dovetailed but reinforced with corner irons inside and out. This battery wagon is used only in connection with the 3-inch gun materiel, model of 1902. Weights, dimensions, etc. Weight of battery wagon, empty pounds 1, 444 Weight of battery wagon, completely equipped and loaded do 2, 947 Diameter of wheels inches 56 Width of track do__ 60 Free height under wagon do L'4. ." Turning angle with limber degrees.- 75 Weight (approximate) at lunette, loaded pounds 112 STORE WAGON, MODEL OF 1902. The store wagon is the same as the battery wagon, model of 1902, with the exception that the vise is omitted and a frame handle at- tached in its place, and the body has but a single compartment, with two doors on top. As on the battery wagon, the store wagon carries two spare wheels and three oil cans. SIDE VIEW OF STORE WAGON. The store wagon is intended primarily for carrying such stores, spare parts, and materials as can be carried in the battery wagon and, in addition, such stores as may be designated by proper authority. Tire brakes are used, operated by a hand lever on the right side of the body. The wheels used and carried are the standard 56-inch wheels. (See page 167.) For detailed description and table of weights, dimensions, etc., see Battery Wagon, page 147. (149) 150 STORE WAGON, MODEL OF 1902 MI. The store wagon, model of 1902 MI, is the same as the battery wagon, model of 1902 MI, with the exception of the differences as noted in the description of the battery store wagon, model of 1902. For detailed description and table of weights, dimensions, etc.. see page 148. 151 FORGE LIMBER, MODEL OF 1902. The frame of the forge limber is identical in all its parts with that of the 3-inch gun limber, model of 1902. It consists of a middle and two side rails, the middle rail being in the form of a split cylinder, one half passing below and the other half above the axle, uniting in front to form a seat for the pole and in the rear to form a seat for the pintle bearing guide. The chest is a rectangular flange-steel box having a lid hinged along the front edge of the chest body. The lid is flanged all around, TOP VIEW SHOWING INTERIOR OF FORGE LIMBER. fitting over the body of the chest to make it water-tight. Shot bolts on the rear face of the chest secure the lid when closed. The interior of the chest is divided into five compartments by four vertical steel partitions. The middle compartment, which is the largest, is fitted to take the field forge, the anvil, and several small tools, the next compartment on either side carries horseshoes and horseshoe nails, and the end compartments are fitted with fastenings for carrying smiths' and machinists' tools. A tubular oil (152) 153 JM 154 can is carried under each end of the chest, and various implements are secured to the chest by straps provided for that purpose. Weights, dimensions, etc. Weight of forge limber, empty, without equipment pounds 958 Weight of forge limber, complete equipped and loaded do 1, 577 Weight of store limber, empty, without equipment do 955 Weight of store limber, complete, equipped and loaded do 1, 106 Diameter of wheels inches 56 Width of track do 60 Free height under limber do ^6. 5 Turning angle with battery wagon degrees 75 FORGE LIMBER, MODEL OF 1902 MI. The forge limber, model of 1902 MI, is identical with the 1902 model, with the exception that the 1902 MI model has an automatic pole support, which is described on page 169. The forge limber is used in connection with the American, British, and French 75-millimeter materiel, and the 3-inch materiel, model of 1902. A detailed description and table of weights and dimensions is given in a preceding article on Forge Limber, model of 1902, page 152. STORE LIMBER, MODEL OF 1902. The store limber is practically the same as the forge limber, model of 1902, except that the chest is fitted with compartments for carry- ing fire-control equipment, some of the compartments being padded to protect the contents from injury. For description and table of weights and dimensions, see preceding article on Forge Limber, model of 1902. TOP VIEW SHOWING INTERIOR OF STORE LIMBER. STORE LIMBER, MODEL OF 1902 MI. The store limber, model of 1902 MI, is identically the same as the store limber, model of 1902, with the exception that it is fitted with an automatic pole support, description of which will be found on page 169. For description and table of weights and dimensions, see preceding article on forge limber, model of 1902. The limber is used in connection with the American, British, and French 75-millimeter materiel, and the 3-inch gun materiel, model of 1902. (355) BATTERY AND STORE WAGON, MODEL OF 1917. The battery and store wagon is made of metal throughout, with the exception of the spokes and felloes of the wheels. The frame is built up of two channel section side rails connected at the rear and intermediate points by similar channels. The side channels are bent inward near the front, meeting and forming a seat in which the REAR RIGHT SIDE VIEW OF BATTERY AND STORE WAGON. lunette bracket is riveted. At the rear of the frame is a compartment for carrying recuperator, lubricating, and coal oil cans. The chest is divided into compartments for carrying various articles of battery equipment. The top compartments have horizontally (156) 157 !! IXHIJXqffl-. :--^-'.yg5jB r liiS- i.'r.-r.-.-i:--.-.-.-.-.-.:.-.-.-.-!-: w;i;djMW l 'iy ^""i iifiligfii Hlllllli8kfe MiSiliisii 158 hinged lids and the lower compartments in front and rear have vertical swing doors. Fastenings are provided on each side of the chest for carrying spare wheels, and provision is made for carrying a spare limber pole. The battery and store wagons are identical, except for the tools and accessories that are carried in the compartments of each vehicle. A vise is carried on the front end of the frame and a crowbar bracket on the right side. The battery and store wagons contain packing strips and accessories for carrying a grindstone in the rear compart- ment. Standard 56-inch wheels are used. (See page 167.) The battery and store wagon is used in connection with the American, British, and French 75-millimeter materiel, and with the 3-inch gun materiel, model of 1902. Wights, dimensions, etc. Weight of battery wagon, empty pounds__ 1, 705 Weight of battery wagon, completely equipped and loaded do 3. 325 Weight of store wagon, empty do 1, 705 Weight of store wagon, completely equipped and loaded do 3, 590 Diameter of wheels inches 56 Width of track do 60 Free height under wagons do 24. 5 Turning angle with limbers degrees__ 75 Weight (approximate) at lunette of both wagons, loaded- pounds__ 112 Overall length inches *132 Overall height do *74 Overall height do *88 * Approximately. BATTERY REEL, MODEL OF 1917. The battery reel, model of 1917, is a single two-wheeled vehicle which is drawn by 4 horses. It is designed to carry, lay, and recover 5 miles of insulated cable, and in addition carries 2 steel chests con- taining fire-control instruments. The frame is composed of two side rails connected by cross members and diagonal braces. Near the front, the side rails converge and are riveted to the pole socket. Axle brackets are riveted to the side rails, LEFT SIDE VIEW OF BATTERY REEL. in which are mounted the axle arms for the wheels and the drum shaft on which the cable drum rotates. On each side of the drum are supports which are joined across the top by a seat for two men. Across the frame in front of the drum is secured an instrument chest divided into two compartments with separate hinged lids, the lids forming foot rests for the personnel on the seat. Across the frame in rear of the drum a large steel chest is supported on springs. It has a lid hinged at the front and provided with guide rollers for the cable at its rear. The larger fire-control instruments are carried in this chest in specially designed com- partments. 5516021 11 (159) 160 On the right side of the drum is secured a steel case in which a plotting board is carried. At either end of the drum is a sliding leather- faced cone which is controlled by a hand lever at the left end of the operator's seat. When either cone is engaged, the other is disengaged. The cone on the left is connected directly to a gear train driven by a gear attached to the wheel hub, and when engaged causes the drum to revolve. As the brake cone on the right is engaged the clutch cone is thrown out of engagement. The wire, when being laid out, leaves from the top of the drum, passing between the guide rollers attached to the rear chest. The cart, model of 1918, together with the reel, model of 1909 MI, is issued in lieu of the battery reel, model of 1917, for motorized batteries. ^eights, dimensions, etc. Overall length (traction pole removed) __inches 74 Overall width do__ _ 73. 7.~i Overall height do__ 65 Weight of reel (without equipment) __pounds__ 1,385 Weight of reel, completely equipped and loaded do 2,005 Diameter of wheels inches 56 Width of track __do__ 60 Free height under reel do__ 19 Length of wire carried (approximately) miles 5 REEL, MODEL OF 1909 MI. The reel, model of 1909 MI, is a two-wheeled vehicle designed to carry, lay, and recover 8 miles of insulated cable. It has interchange- able pole connections which enable it to be adapted to either horse or motor traction. The frame is composed of special shaped pressed steel members connected by gusset plates and reinforce pieces, the pole socket at the front, automatic pole support, a pintle at the rear, and the assem- bled axle. REAR VIEW OF REEL. Two drums which carry the cable are mounted end to end on an axle which rests in the upper ends of the axle brackets. In order to lay the wire, the drums are disengaged from the clutch, permitting them to revolve free upon their axes, but controlled by the braking action of the drum latch and drum brake or the friction clutch when applied for that purpose. To recover the cable or wind it on the drums, the clutch in the right drum is applied, and the drum made to revolve, by means of the chain driving gear attached to the right wheel. The left drum is driven by the right drum through a pin clutch which is operated by a handle in the left outer end of the left drum. (161) 1(12 163 An operator's seat is secured to the right rear corner of the frame, and the controls placed within easy reach. The clutch connecting the drum driving gear and the right drum is located in a recess in the right drum head and operated by a handwheel at the upper end of a shaft mounted on the right axle bracket. A lever on the right side near the seat operates the drum latch for locking the right drum, and, through the pin clutch, the left drum when they are at rest. A leather faced brake shoe attached to the drum latch lever may be brought against the flanged rim of the right drum end plate to act as a brake. A brake shoe controlled by a foot lever near the operator's seat may be brought to bear against the flanged rim of the left drum end plate. FRONT VIEW OF REEL. Wooden rollers are placed under the frame so that the wire will be laid out or recovered without injury to it. A tool box with lid opening on top is secured to the right of the pole bracket in the space between the side rail and front cross rail. The reel, model of 1919 MI. together with the cart, model of 1918. is issued in lieu of the battery reel, model of 1917, for motorized batteries. Wcif/hts, dimensions, etc. Weight of reel (without load) -__pounds__ 1.459 Weight of reel completely equipped and loaded do 2,426 Diameter of wheels inches 56 Width of track __do 60 Free height under reel r do 19 Turning angle with cart degrees 75 Length of wire carried __yards__ 22, 880 CART, MODEL OF 1918. The cart is a two-wheeled vehicle made of metal throughout, with the exception of the spokes and felloes of the wheels and the packing '. - : ' " "" VIEW SHOWING REEL AND CART, LIMBERED. within the chest. It is designed to carry part of the fire-control equipment for the organization to which it is issued. REAR VIEW OF CART. The frame consists of a middle rail, two side rails, and two axle brackets, all of which support the chest. The forward end of the (164) 165 166 middle rail is fitted with a lunette and the rear end with a pintle. Spiral springs are interposed between the side rails and axle brackets to absorb the shocks when traveling. In connection with the axle brackets, Belleville springs are used to take up rebound. The chest is made up of flange steel plates riveted together and fitted with doors, lock bars, and packing devices, the interior being divided into 17 compartments of different sizes. The chest is also furnished with fixtures on the exterior for attaching an observation tower. The road brakes are of the contracting band type and are operated from the front of the cart or from the operator's seat on top of the chest by means of a brake lever on the right side. This cart, together with the reel, model of 1909 MI, is issued in lieu of the battery reel, model of 1917, for motorized batteries. Weights, dimensions, etc. Overall length inches-- * 126 Overall width do__ * 74 Overall height do__ * 62 Weight, empty, without body equipment pounds 1,676 Weight, complete fully equipped and loaded do 2, 004 Diameter of wheels? inches* 56 Width of track do 60 Free height under cart (approximate) do 26 Turning angle with reel (approximate) degrees Weight of instruments pounds 431 * Approximately. THE 56-INCH WHEEL. All carriages and accompanying vehicles of the 3-inch and 75- millimeter materiel, of American design, are equipped with standard 56-inch wheels, which are interchangeable for all vehicles of these materiels. The wheel is a modified form of the Archibald pattern, 56 inches in diameter, with 3-inch tires. The tires are of steel. An oil valve is provided so that the wheel can be oiled without removing it. SIDE VIEW OF WHEEL. The wheel fastening consists of a bronze yoke fitting in the outer end of the axle arm and is accessible when the hub cap is removed. THE 57 BY 3.5-INCH WHEEL. In place of the above 56-inch wheel a 57 by 3.5-inch wheel may be used. It is similar in design to the 56-inch wheel, but is fitted with solid rubber tires. Like the 56-inch wheel it is interchangeable on all vehicles of the 3-inch and 75-millimeter materiel. (167) REEL, MODEL OF 1917, FOR CAISSONS. One caisson in every battery is provided with a hand reel for tele- phone wire. It is riveted to the top of the caisson and contains 1 mile of field wire so arranged that the current goes through all the wire. Terminals are provided for the connection of the instruments. The reel for caisson, model of 1917, is a hand-operated reel for the transportation and handling of telephone wires. REEL, MODEL OF 1917, FOR CAISSONS, MOUNTED ON A CAISSON. The frame is built up of two flanged steel ends and two sides, riveted together with four angle-iron corner reinforces, and riveted to the top of the chest. The reel is built up of two, steel, spool flanges mounted on a shaft, a spool riveted to the right flange and a basswood spool hub mounted between the spool flanges. The spool may be operated from either side. The crank on the right side is mounted on the shaft, and when not in use it can be removed and placed in its provided receptacle. The crank on the left side is connected with the spool through an 18 to 40 gear reduction. The crank shaft is fitted with a driving gear which meshes with a pinion on the shaft of the spool. Chains are provided on either end of the frame for locking the cranks when not in use. (168) 169 The reel is also fitted with a brake for controlling the speed of rota- tion when allowing wire to run out. The brake lever is pivoted on the brake-lever pin, and operated by a thong attached to the lower REEL FOR CAISSON, MODEL OF 1917. end of the lever. By pulling the thong the upper end of the lever is made to drag on the inside of the rim of the left spool flange. A brake-release spring, attached to the upper end of the lever, and a lug on the left shaft bearing, keeps the brake open when not in use. THE AUTOMATIC POLE SUPPORT. Late designs of limbers for 75-millimeter and 3-inch gun materiel are fitted with an automatic pole support. The pintle hook has a lug formed on its lower side, which projects backward and bears against the lower side of the lunette on the drawn vehicle, thus preventing the vertical rotation of the pintle. SECTIONAL DIAGRAM OF POLE SUPPORT. The pintle bearing is pivoted by trunnion bolts permitting rota- tion in the vertical plane. A spring rod is pinned to a lug on the top of this bearing and carries the pole supporting springs. This spring is held between a collar on the rod and the pintle bearing guide so that when the weight of the pole on the coupled vehicle is put on the pintle it tends to compress the spring until the load is supported by it. On the pintle bearing bolt is another spring, which is compressed when the pintle is drawn back, thus relieving the shock of starting. 170 105-MILLIMETER HOWITZER MATERIEL, MODEL OF 1898-09 (GERMAN). The 105-millimeter howitzer materiel, model of 1898-09 (German), is entirely a German product in design and manufacture. The car- riage has several unique features and differs in a number of respects from any other carriage described in this book. The cradle and howitzer are so mounted that the breech of the howitzer is practi- cally at the axis of elevation. This permits loading at any angle of elevation without the necessity of raising or lowering the piece in order to insert ammunition. Because of the opening in the trail, the piece is permitted to recoil at high angles of fire, and on account of the howitzer being hinged at the breech a constant recoil can be maintained and the trunnions are kept at a minimum height above the ground. This location of the trunnions, of course, necessitates the use of an equilibrator spring to balance the overhang of the elevating parts. This is interposed between the trail and the cradle. This carriage seems to have been very satisfactory, as the German Army made very extensive use of it during the World War, mount- ing three different types of guns on this same type of carriage a long and a short model of 105-millimeter field howitzer and a 77-millimeter field gun. The Germans do not appear to adhere to the type, once it was adopted, as firmly as did the French to their Model 1897. There are certain changes made in the manufacture of this carriage, and no system seems to have been followed in applying them. To illustrate, there are two distinct types of shields, three different types of cradles, some of which are provided with an elevation stop, and three types of top carriages. The later type of car- riage has a double lunette, the top of which is hinged, and an ice prong is added to the rear of the trail. These changes, however, do not affect the use of the carriage for either of the three types of guns mentioned. The howitzer now in the United States for this carriage is known as the 105-millimeter howitzer, model of 1916 (German). It has a muzzle velocity of 1,402 feet per second and a maximum range of 10,930 yards, the projectile weighing approximately 35 pounds. Separate loading ammunition is used. The recoil mechanism used is the hydrospring type. It consists of a hydraulic-brake cylinder, a spring return, and a continuous-act- (171) 172 ing buffer. The length of recoil is approximately 51 inches and is constant. The maximum elevation possible is 40, with a 10 depres- sion. A slight traverse is permitted a total of 4. The battery equipment of each howitzer carriage consists of the following : 105-millimeter howitzer, model of 1916 (German). 105- " carriage, model of 1898-09 (German). 105- howitzer caisson, model of 1898 (German). 105- " howitzer carriage and caisson limber, model of 1898 (German). VIEW SHOWING CARRIAGE LIMBER AND CAISSON, COUPLED. Weights, dimensions, ballistics, etc. Weight of howitzer with breech mechanism pounds 985 Weight of breech mechanism do 70 Weight of carriage only do 2,270 Weight of howitzer and carriage in firing position do 2,950 Total length of howitzer inches__ 90.9375 Length of tube do 82. 125 Length of tube calibers 19. 87 Number of rifling grooves 32 Diameter of wheels inches__ 48 Width of tire do 3. 25 Weight of wheel pounds 190 Track gauge inches 61 Height of axis of gun above ground do 41 Height of trunnions above ground do 34 Road clearance do 16 Over-all length, muzzle to center line of lunette do 189. 25 Elevation, total degrees Minus 10 to plus 40 Traverse, total degrees 4 (71.10 mils.) 105-MILLIMETER HOWITZER AND CARRIAGE, MODEL OF 1898-09 (GERMAN). The howitzer consists of three pieces, a tube, a jacket, and a clip hoop. The tube is the foundation of the howitzer and in it is formed the powder chamber. The breech end of the tube is reinforced by the jacket, on the bottom of which at each end clips are formed integral with it. The clip hoop is forced on the tube near the center of its length and provides the forward clip. FRONT VIEW. SHOWING BRAKES AND TRAVELING LOCK. The breech block is the sliding wedge-block type and is operated by a lever placed on the upper right side of the breech and operated in a horizontal plane. The firing mechanism is the continuous-pull type, the mechanism being both cocked and fired by one pull of the lanyard. The recoil cylinder recoils with the howitzer. It is held thereto by the howitzer retaining nut. This nut is locked in position by a (173) 174 Illllllll QU.(oc8t(j 175 locking plug. The rear end of the cylinder is sealed by the rear cylinder head and a copper gasket. The head contains the filling plug and is locked to the cylinder by a headless set screw. Twelve throt- tling grooves of varying depth are cut lengthwise in the interior surface of the cylinder wall. The front end of the piston rod screws into the cradle cap, so that during recoil the piston and rod remain stationary while the cylinder moves to the rear with the gun. The piston rod is hollow to within a few inches of the front end. The buffer, also hollow, is screwed into the rear cylinder head and is locked by a set screw. When assembled in the cylinder the buffer fits inside the hollow piston rod. Two small throttling grooves are cut lengthwise in the buffer. A ball check valve is located in the rear end of it. On the front end of the recoil cylinder there is a turned shoulder that holds the front inner-spring retainer in position when the springs are assembled. The front cylinder head is screwed in position against a copper gasket and is locked by a leaf spring. This head forms a stuffing box for the piston rod and contains a bronze packing ring, leather and babbit metal packing, and the stuffing box nut, which is locked to the cylinder head by a leaf spring. The counter recoil mechanism consists of two spring columns, one outer and one inner, of three springs each placed end to end. In re- coiling the cylinder compresses the inner spring against a rear spring retainer. This retainer gives the load to a spring stirrup which in turn gives the load to an outer-spring retainer, thereby compressing the outer-spring column. The outer-spring column impinges on the rear end of the cradle. The outer-spring retainer has extensions on each side that move in guides in the cradle. When the piece is fired, the recoil cylinder moving to the rear while the recoil piston remains stationary, forces the liquid to move past the piston to the rear. The only orifice for its passage, in addition to the slight clearance between the piston and the cylinder wall, is through the throttling grooves cut in the cylinder wall. The depth of the grooves is varied so that the orifice area is such that the movement to the rear is opposed by a practically constant force throughout its entire length. As the recoil cylinder moves to the rear the buffer moves out of the piston rod, creating a vacuum therein and causing the ball valve to open, permitting some of the liquid, which has passed the piston, to flow into the hollow piston rod, so that at the end of recoil this space is completely filled. When the end of the backward movement is reached, and the compressed counterrecoil springs act to return the piece to battery, the ball rolls to the rear, closing the valve in the buffer rod, permitting the escape of the liquid in the hollow piston rod only through the 5516021 T2 176 clearance space around the buffer and through the two small axial grooves. With the movement back to battery, the liquid in the rear of the piston head, of course, returns past the piston to the front of the cylinder, but the force of counterrecoil stored in the springs is absorbed mainly by the throttling of liquid in the hollow piston rod, causing the piece to return to battery without shock. The cradle is constructed in the shape of a tube of " U " section made from sheet steel and having the top covered by a piece of rolled or forged steel of such a shape as to form guides the full EQUILIBRATOR MECHANISM. length of the cradle, upon which the howitzer is supported and upon which it moves during recoil. The recoil mechanism is contained within the tube thus formed. The trunnions are riveted to the cradle at the rear end and two elevating segments, one on each side, are bolted to it. A spring equilibrator designed to counterbalance the overhanging weight of the tipping parts is interposed between the trail and cradle. The spring column consists of an inner and outer spring so connected by a stirrup as to work in series. One end of the column bears against a seat on the trail and the other end bears against a seat on the under side of the cradle, both seats being of the ball and socket 177 type. The force of the spring very nearly balances the turning moment of the, overhanging howitzer and cradle whan at zero elevation, so that very little effort is required to elevate the piece. The top carriage is built up of two side flasks of pressed steel connected at the front and rear by steel transoms. On the bottom of the front transom is a pintle which sets into a pintle bearing on the trail. Riveted to the lower rear end of each flask is a clip. These top carriage clips fit into two trail clips and are supported on small ball races making traversing easy. The trunnion bearings are attached to the upper flanges of the flasks near the rear. The top carriage also carries the elevating mechanism. REAR VIEW OF CARRIAGE. Elevation is accomplished by the double gear segments on the cradle, operated through a train of gears by a handwheel on the left side of the top carriage. The maximum elevation is 40 ; the max- imum depression, 10. Traverse is accomplished by causing the top carriage to rotate about the pintle. This is done by means of a screw fixed to the top carriage and a threaded handwheel revolving in a bracket attached to the left side of the trail. The traverse is 2 each side of the center. The trail is provided with a rock spade and a soft earth spade. The latter folds under the trail when not in use. To prevent strain on the elevating and traversing mechanisms when traveling the cradle is locked to the trail by a locking device pivoting on the trail and engaging clips on the under side of the cradle. Shields of armor plate are provided for the protection of the personnel. 178 The wheels are of wood, 48 inches in diameter and fitted with steel tires. The carriage is equipped with a pair of tire brakes acting directly on the tires of the wheels. Sighting is accomplished by means of a quadrant .sight. This Ger- man quadrant sight is similar in basij principle and method of operation to the quadrant sight, model of 1918 (Schneider), the type of combination sight and quadrant that is standard equipment of the heavy artillery. The complete unit consists of a sight mount and a panoramic telescope, which furnishes the optiral element for the unit. The sight is of the dependent-line-of-sight type. It is attached to the left trunnion of the cradle on an extension provided for that purpose. Separate-loading ammunition is used in this howitzer. Only Ger- man ammunition has been issued. The shells are of the high ex- plosive and illuminating-star-shell types. Propelling charges con- sisting of flaked powder (Wuerfelpulver) are made up in bags and enclosed in brass or steel cartridge cases with detachable pasteboard or cork covers. Flash reducers are used for night firing. They create a dense smoke cloud, thus masking the flame. There are three types of fuzes, two of which are percussion fuzes, and the other is a 22-second time fuze. The latter is used on the illuminating shells. 105-MILLIMETER HOWITZER CAISSON, MODEL OF 1898 (GERMAN). Weight, complete, empty _.-i>ouml$__ 1,079 Weight of tools and equipment carried do Weight, completely equipped and loaded do 2, 435 Rounds of ammunition carried in caisson chest 28 Diameter of wheels inches 53 Width of track __do 61.25 105-MILLIMETER CARRIAGE AND CAISSON LIMBER, MODEL OF 1918 (GERMAN). Weights, dimensions, etc. Weight, empty pounds 826 Weight of tools and equipment carried do Weight completely equipped and loaded do 2, 035 Rounds of ammunition carried in limber chest 26 Weight at end of pole fully equipped and loaded- Diameter of wheels inches__ 53 Width of track do 61.25 Length, center of pintle to center of wheel do 31. 75 179 FRONT AND REAR VIEWS OF 105-MILLIMETER CARRIAGE CAISSON LIMBER. MODEL OF 1898 (GERMAN). 180 FRONT AND REAR VIEW OF 105-MILLIMETER HOWITZER CAIS- SON. MODEL OF 1898 (GERMAN). 4.7-INCH GUN MATERIEL, MODEL OF 1906. The 4.7-inch, model of 1906, is a mobile field gun, designed to fire shrapnel or shell at greater ranges than the 75-millimeter guns. In order to increase the range, a 45-pound shell is provided to replace the old type 60-pound shell. The former projectile gives consider- ably higher muzzle velocity and longer range than the 60-pound pro- jectile. The life of the gun before relining is approximately 5,000 rounds. Using the 60-pound shrapnel, a muzzle velocity of 1,700 foot- seconds is obtained, with a maximum range of 7,550 yards (6,903 meters) at an elevation of 15. With the 45-pound shell, a muzzle velocity of 2,050 foot-seconds, and a maximum range of 8,700 yards (7,900 meters) is obtained at an elevation of 15, under normal conditions. VIEW SHOWING CARRIAGE AND LIMBER IN TRAVELING POSITION. The 4.7-inch field gun is mounted on a carriage of the long-recoil type, in which the gun is permitted a sufficient length of recoil on the carriage to render the latter practically stationary under firing stresses. The gun, in recoil, is controlled by two spring cylinders, and a hydraulic cylinder, which is filled with 25^ pints of oil. In recoil, the oil in the hydraulic cylinder is forced from one side of the piston to the other through small portholes. The area of these ports are calculated to make the resistance which the liquid offers, plus the resistance of the springs, such that the wheels will not jump from the ground when the gun recoils. In counterrecoil the oil is forced back through these small ports with the result that the return of the gun into battery is so eased and regulated that shock and consequent derangement of the aim is almost eliminated. To properly return the gun to battery at high angles of elevation, the springs are assem- bled with an initial compression of approximately 1,500 pounds in each cylinder. (181) 182 183 184 The carriage is equipped with a single trail, composed of two pressed steel flasks, and is anchored in the ground by a spade when in action. When traveling, the trail is supported by the carriage limber, which may be drawn by either a truck or tractor. On account of the single trail the maximum elevation of the gun, without digging in the trail, is only 15. The allowable transverse movement is 140 mils, or about 8. The motorized equipment of each gun carriage, as indicated below, consists of a carriage limber, which supports the trail when traveling, and three caissons, which carry ammunition. 4.7-inch gun and carriage, model of 1906. 4.7-inch gun carriage limber, model of 1905. 4.7-inch gun caisson, model of 1916 or 1917. The above materiel is entirely of American design and manufacture. LEFT FRONT VIEW OF CARRIAGE EQUIPPED WITH BAND BRAKES. Weights, dimensions, and ballistics. Weight of gun pounds 2.688 Total length inches 134. 927 Rifling Right hand, 1 turn in 50 calibers at origin to 1 turn in 25 calibers at 14.9 inches from muzzle, thence uniform. Weight of projectile, base fuzed shell and shrapnel pounds 60 Weight of point fuzed shell do__ 45 Weight of powder charge ounces 95 Weight of cartridge case pounds Muzzle velocity (60 pound shell and shrapnel) ft. per sec 1, 700 Muzzle velocity (45 pound shell) do 2,050 Maximum range at 15 elevation of 45-pound shell yards 8, 700 Maximum range at 15 elevation of 60-pound shrapnel do 7, 550 Weight of carriage, complete (without gun) pounds 5,320 Weight of gun and carriage, fully equipped do 8, 069 Diameter of wheels inches 61 Width of wheels do 6 Height of axis of gun do 51. 59 Maximum angle of elevation (gun or carriage) degrees-- 15 Maximum angle of depression (gun or carriage) do 5 Amount of traverse mils 140(7.8) Height of line of sight inches 53. 92 185 186 4.7-INCH GUN AND CARRIAGE, MODEL OF 1906. TJie gun is of the built-up type, and consists of a tube, jacket, lock- ing hoop, and clip. The jacket covers the rear half of the tube, and projects beyond the tube at the rear to form the breech recess. The FRONT VIEW OF CARRIAGE EQUIPPED WITH TIRE BRAKES. jacket is equipped with a recoil lug on the underside for connecting the recoil cylinder. The clip is a short hoop near the muzzle and is fitted with guides to guide the gun in the cradle on recoil. BREECH MECHANISM. The breechblock is of the interrupted screw type, having four threaded and four plain sectors. It is operated by a handle which swings from left to right, turning and withdrawing the breech with one motion. An extractor is fitted for throwing out the shell case when the breech is opened after firing. 187 The firing mechanism is of the type known as a continuous-pull mechanism ; that is, the mechanism is cocked and fired by the pull on the lanyard or by downward pressure on the firing handle located at the left side of the breech. The carriage is composed of the following principal parts : Wheels, axle, the cradle (for housing and supporting the recoil mechanism of the gun), trail, traversing and elevating mechanisms. The gun carriage is of the long-recoil type, in which the gun is permitted to recoil on the carriage to render the latter stationary under firing stresses. The recoil mechanism consists of an hydraulic cylinder filled with oil, placed parallel to the gun, and attached to the cradle. The recoil cylinder controls the backward movement of the gun upon discharge, and the springs function to return the piece to battery position. FIRING MECHANISM. The recoil and counterrecoil mechanism is of the hydrospring type, and consists of two parallel steel tubes (the spring cylinders) fitted into a frame and surrounded by rails which form the gun slides and the cradle. The recoil cylinder is fitted between these two. The piston and spring rods are secured to the gun lug and recoil with the gun, while the spring cylinders and recoil cylinder remain stationary. The recoil is of the constant type, being 70 inches when the gun is fired at zero elevation, and is somewhat greater at higher angles, due to the action of gravity on the recoiling parts. The recoil cylinder uses hydroline oil as the buffer medium. Throttling is obtained by three throttling bars running lengthwise of the cylinder, which are of varying height to give a throttling effect with corresponding slots in the recoil piston. A counterrecoil buffer is fitted in the piston rod to take up the shock when the springs return the gun to battery. 188 189 The trunnions on the cradle are mounted in bearings formed by a yoke which swivels in a pintle bearing provided at the front of the trail. Traverse is obtained by means of a handwheel and screw mounted on the left side of the trail, which swings the yoke, it carrying the gun with it. A traverse of 70 mils on each side of center is possible. The piece is elevated by a double screw type of mechanism. The upper end is attached to the cradle and so raises and lowers it. The screw is operated through gearing by two handwheels, one on FRONT VIEW OF CARRIAGE EQUIPPED WITH BAND BRAKES. each side of the trail. From 5 degrees depression to 15 degrees elevation is obtained. The trail is of the solid type, made up of flasks of channel section. It houses the axle and carries the pintle bearing in which the top carriage, or yoke, swings. A tool box is fitted in the trail, and a seat is provided on each side of the trail for the cannoneers. The lunette transom is fitted about 27 inches from the rear of the trail, and carries a bearing that fits the limber pintle. A trail prop is provided for supporting the trail when limbering. The spade can be released and folded up on the trail when traveling. 190 A traveling lock is provided on the trail for locking the gun when traveling. The piston rod and spring rods must be disconnected before the gun can be drawn back far enough to lock. . REAR RIGHT SIDE VIEW OF CARRIAGE. The wheels are 61 by 6-inch, rubber tired, and are equipped with band brakes. Some of the older type of vehicles have steel tires and ELEVATING AND TRAVERSING MECHANISMS. are fitted with tire brakes. An armor plate shield is fitted to the carriage for the protection of the personnel. The sighting is similar to the 3-inch gun, model of 1902. The instruments for sighting and laying the piece include line sights, a rear sight, a front sight, a panoramic sight, and a range quad- rant. 191 o 5516021 13 192 The line sight consists of a conical point as a front sight, and a V-notch as a rear-sight. These are located on the jacket of the gun, and are useful for giving general direction to the gun. The rear and front sights are used for direct aiming. The rear sight is a peep sight mounted on range scale shanks on left side REAR VIEW OF CARRIAGE EQUIPPED WITH TIRE BRAKES. of the cradle. The front sight consists of a pair of cross wires mounted in a ring about three feet ahead of the rear sight. The sight shank has a socket in which the standard United States panoramic sight may be mounted. On the right side of the cradle is mounted the range quadrant, which has in combination with it the angle of sight mechanism. For indirect fire the gunner on the right of the piece lays for range with this instrument, and the one on the left lays for direction only. 193 X i p' V ) "~~ / 1 IV <&P u B ^ L i L L, 5 u 1 ' J 1 c i \ ] i J , I 5 r 194 Fixed ammunition is used with this gun; shrapnel and high ex- plosive shell being used. The base fuzed steel shell and the shrapnel FRONT VIEW OF CARRIAGE EQUIPPED WITH TIRE BRAKES. weigh 60 pounds. The point fuzed shell weighs 45 pounds. Gas shells are also issued and are identical with the 45-pound steel shell. 4.7-INCH GUN CARRIAGE LIMBER, MODEL OF 1905. The limber, a two-wheeled vehicle to which the trail of the car- riage is fastened, forms with the gun carriage, a four-wheeled car- riage for the gun when traveling. The carriage limber is designed to be used with the connecting pole for attachment to a tractor and to support the trail in traveling. The limber is made of metal throughout, wood being used only in the spokes and felloes of the wheels. The principal parts are the wheels, axle, frame, top carriage, pole socket, and connecting pole. The top carriage is a steel casting, formed to accommodate the trail of the 4.7-inch gun carriage, the trail resting on it when en route. FRONT VIEW OF LIMBER. The front end of the top carriage is provided with three rollers which rest, and run on, the top carriage rail ; the rail edge being equipped with clips to prevent accidental dismounting. A spur located on the top carriage which enters the trail holds the trail and top carriage in line. The wheels are 51 inches in diameter, 4 inches wide, and are rubber tired. The hubs are similar and interchangeable with those on the wheels of the carriage. The axle is hollow and is made from a single piece of forged steel. A bucket holder with straps is located on each side brace for car- rying four canvas watering buckets. (195) 19(5 197 The doubletree, singletrees, and pole complete are omitted for motorized batteries and a connecting pole is used in their place. The standard short pole with lunette is fitted for motor traction, and for horse-drawn equipment the longer pole may be substituted. Weights and dimensions. Weight, complete, including spare connecting pole pounds 1, 750 Weight of limber with gun and carriage, traveling position do 9, 818 Diameter of wheels (rubber tired) inches 51 Width of track do 60 Free height under limber and carriage do 16. 8 4.7-INCH GUN CAISSON, MODEL OF 1908. The 4.7-inch gun caisson is constructed upon the same general plan as the 4.7-inch caisson limber. The wheels, axles, pintles and bearings, lock bars, and most of the implement fastenings and chest parts of the two vehicles are exactly similar and interchangeable. The principal parts of the caisson are the wheels, axle, axle bearings, ammunition chest, pintle, connecting-pole socket, connecting pole, prop, apron, and brake. The flange-steel front plate and chest door (upper) of the limber are, on the caisson, replaced by armor plates, for the protection of RIGHT SIDE VIEW OF CAISSON. ammunition servers from small arms and shrapnel fire. An apron of armor plate is hinged to the bottom of the caisson chest and extends to within a short distance of the ground for the same purpose. This apron swings forward against the bottom of the ammunition chest to clear obstructions in traveling, and is held in that position by latches attached to the sides of the chest. The pole socket of the caisson is made longer than on the caisson limber, and is fitted with rollers which serve as wheel guards. The connecting body is made of steel tubing, its rear end is finished to fit the pole socket, and is provided with a seat for the rectangular key which secures the connecting pole to the socket. A prop of (198) 199 steel tubing with a bronze foot is attached to the connecting pole for a support when the caisson is unlimbered ; when not in use the prop is swung up under the connecting pole and is held by chains. The beams of the road brake are hinged in brackets riveted to the chest front. The brakes are built up of flange and forged steel parts and carry cast-iron shoes to bear against the wheel tires. Hangers for a spare connecting pole and a bracket for a spare key are provided on the chest. The ax, hatchet, lantern, and watering bucket fastenings are similar, and located like those on the caisson limber. The paulin on the caisson chest serves as a seat cushion, and on either side of the chest handrails provide handholds for the cannoneers, when mounting or dismounting. The opening between the upper and lower intermediate plates on the left side is utilized to carry a two-gallon oil can. Of every four caissons, three carry oil cans containing lubricating oil, and the fourth, hydroline oil, the contents of each being indicated by a name plate. Weights, dimension, etc. Weight of caisson limber, empty (without implements or ammu- nition) pounds 1, 821 Weight of implements carried do 85 Weight of ammunition carried : do 2, 055 Weight of limber, fully equipped and loaded do 3, 961 Weight of caisson, empty (without implements or ammunition) do 2,058 Weight of implements carried (including spare connecting pole) do 147 Weight of caisson fully equipped and loaded do 4, 260 Rounds of ammunition carried in caisson limber 28 Rounds of ammunition carried in caisson 28 Diameter of wheels . inches 60. Width of track do 60. Free height under caisson do 19. 55 Turning angle degrees 80 4.7-INCH GUN LIMBER, MODEL OF 1908. The limber is a two- wheeled vehicle provided with an ammunition chest for the transportation of ammunition for the 4.7-inch gun. The principal parts are the wheels, axle, ammunition chest, pintle, pole socket, pole, doubletree, singletrees, and neck yoke. The wheels and the wheel fastenings are the same as, and are inter- changeable with, those on the carriage. The axle is hollow and of a single piece of forged steel. It is secured to the chest by axle bearings riveted to the sides of the chest and to the flanges of the intermediate plates. The ammunition chest is built up of flange steel and is divided into an upper and lower compartment by intermediate plates. Cor- VIEW SHOWING GUN CAISSON AND LIMBER, LIMBERED. responding holes in the middle and rear diaphragms are connected by conical brass tubes called connecting pieces, which are cut away on top to save weight. These connecting pieces support the front end of the cartridge case and serve to guide the projectiles. The chest doors close against the heads of the cases so that the cartridges are firmly held in position. Suitable clearances are cut in the flange of each cartridge pocket to enable the cartridge hook to get back of the rim of the case in withdrawing it from the chest. The doubletree is mounted upon a doubletree pin projecting up through a boss on the forward end of the pole socket. A limber prop is hinged to the pole socket. When traveling, the prop is drawn up to the rear and held by a chain. The pintle swivels 360 in the bearing, but is normally held in a vertical position by a spring bolted to the pintle bearing support. (200) 201 The right side of this vehicle is equipped with fixtures for holding a pick, hatchet, and pickax; while on the left side provision is made for a shovel. The paulin on the top of the chest is held in place by straps suitably fastened. Other fastenings on top of the chest are for a picket rope, an ax. and a limber blanket. On the front are attachments for a wrench and a pole prop. The cartridge hook for use in withdrawing the cases and projectiles from the chest is fastened on the left side of the caisson. A spanner for tightening the hub bands of the wheels is carried between the intermediate plates. The pole, doubletree and singletrees, and neck yoke are standard and interchangeable with those on any limber of the battery. Double- tree chains attached to the chest body prevent excessive movement of either end of the doubletree. The 4.7-inch gun limber, model of 1908, is only used in connection with the 4.7-inch gun caisson, model of 1908, both being of American design and manufacture. These vehicles are used with motorized as well as horse-drawn batteries of 4.7 inch gun materiel. 4.7-INCH GUN CAISSON, MODEL OF 1916. The caisson, model of 1916, is a two-wheeled vehicle with an armored ammunition chest for the transportation of ammunition for the 4.7-inch gun. This vehicle is designed to carry 28 rounds of the fixed type of ammunition. The body is suspended in such a manner that 7 rounds are carried below and 21 above the axle. RIGHT FRONT VIEW SHOWING CHEST DOORS OPEN, EXPOSING DIAPHRAGMS. The chest is built entirely of steel, but the upper door, rear plate, and an apron hung under the body are of armor plate for protection of the ammunition servers in the rear from shrapnel and small-arms fire. The doors open to the front, and when closed bear on the heads of the shells. Suitable fastenings are provided on this chest for carrying the usual complement of tools and accessories, also brackets (202) 203 204 for carrying fuze boxes on the outside of the chest. The chest pro- vides seats for two cannoneers. This caisson is provided with an ammunition chest of sufficient size to carry either shrapnel or high-explosive steel shells. It is also equipped with fixtures for holding picks, shovels, and other tools on the outside of the ammunition chest. By removing the connecting pole, and adding double and singletrees, this vehicle may be trans- formed into a caisson limber suitable for horse traction. FRONT VIEW OF GUN CAISSON. The principal parts of the vehicle are the wheels, axle, ammunition chest, pintle, brake, connecting pole socket, and connecting pole. The wheels and wheel fastenings are the same as, and are inter- changeable with, those on the carriage. The axle is fastened to the chest by axle bearings riveted to the chest sides. The body of the chest is of flange steel riveted together, forming the top, bottom, and sides of the chest. The chest doors close against the heads of the cases so that the cartridges are held firmly in posi- tion. Suitable clearances are cut in the flange of each cartridge 205 pocket to enable the cartridge hook to get back of the rim of the case in withdrawing it from the chest. The chest doors open to the front, the lower door being hinged to the bottom of the chest, the upper to the top of the chest, and by means of a lock bar the doors are locked. The armor-plate apron is hinged to the bottom of the caisson, so that when traveling it may be swung backward against the bottom, where it is held by latches on the chest sides. The vehicle is equipped with a short connecting pole in front pro- vided with a suitable prop for holding the pole up when the caisson is at rest. At the rear is the standard pintle enabling other vehicles to be connected en train. On the tire brake models, brackets are riveted to the end of the chest. To these brackets are pinned the brake beams by the same kind of leverage system as on the carriage. The brake shoes are brought to bear on the tire by pressure on the brake lever, the brake lever and segment being on the left side of the vehicle. The brake band model, like the tire brake, has the brake lever on the left side of the chest and is of the contracting-band-brake type. Pulling up on the brake lever causes the brake bands to grip the drums bolted to the wheels. The top of the chest has provision made for carrying a picket rope and spare connecting pole, an ax, and straps for holding a paulin. The paulin serves as a seat cushion. The left side carries the pick, mattock, and hatchet; the right, a long-handled shovel, cartridge hook, and pole socket key. On the back are riveted a bucket holder, lantern bracket, and a foot rest. Between the intermediate plates in front an oil can is carried on the right side, a fuze box on the left, and also a spanner wrench. In every battery one caisson is provided with a hand reel containing 1 mile of wire as for caisson model of 1917. (See page 168.) Weight, dimensions, etc. Weight of caisson, empty with implements pr ammunition pounds 2, 565 Weight of implements carried, including spare constructing pole do 180 Weight of ammunition do 2,067 Weight of caisson fully equipped and loaded do 4812 Round of ammunition carried 28 Diameter of wheels inches 61 Width of track do 60 Free height under caisson do__ 20. 8 4.7-INCH GUN CAISSON, MODEL OF 1917. The caisson, model of 1917, is a two-wheeled vehicle equipped with an armored ammunition chest for the transportation of ammuni- tion for the 4.7-inch gun. The two most important changes from previous models are: The substitution of a band brake for a tire brake, and a spring support for the ammunition chest. The principal parts of the caisson are : The wheels, axles, spring support, ammunition chest, brake, pintle, and connecting pole. The wheels are 60-inch, steel tired with standard hubs and fasten- ers. The axle is a hollow single piece of forged steel. A distin- guishing feature of this caisson is the spring-supported chest. Suit- able brackets are provided on the chest, and arms on the axle for carrying spiral springs to take up road shocks. The ammunition chest is built up of flanged steel, except the rear plate, apron and chest doors, which are of armor plate. The body of the chest is made of two sheets of flanged steel formed to shape and joined at the sides. Three vertical diaphragms with connecting pieces provide an even distribution of the load of ammunition. The upper door when raised is held at about a 60 angle. The lower door is made with an armor plate apron hinged to its top edge, so that when it is dropped, it forms, with the upper door and rear plate, an armor-plate protection. The road brake is of the contracting-band-brake type and is oper- ated from the right side of the chest by pulling up on the brake lever; this through a linkage causes the brake bands to grip the drums of the wheels. The connecting pole is attached to the caisson by a socket, the inside being tapered to accommodate the rear end of the connecting pole, also the horse pole. The foot rests of commercial flange steel are riveted to the upper chest door; these also serve as handles in opening and raising the door. A lantern bracket, and fastenings for holding a pick, shovel, lunette, and spanner wrench are riveted to the rear plate. At the top are riveted fastenings for holding an ax, connecting pole; also strap fastenings for the paulin and the caisson blankets. A car- tridge hook and hatchet fastenings are riveted to the left side of the chest. Of every four caissons three carry lubricating oil and one hydroline oil. One caisson in every battery is provided with a reel for caisson, (206) 207 5516021- -14 208 model of 1917, which is riveted to the top of the caisson and contains 1 mile of field wire for telephoning purposes. (See page 168.) By changing the connecting pole and adding the doubletree and singletrees this caisson is converted into a caisson limber. A standard pintle with a semiautomatic latch is provided at the rear. Weights and dimensions. Weight of caisson, empty, without implements or ammunition pounds 2, 053 Weight of implements carried, including spare pole do 180 Weight of ammunition do 2, 067 Weight of caisson fully equipped and loaded do 4, 300 Rounds of ammunition carried 28 Diameter of wheels inches 60 Width of track__ __do__ 60 5-INCH, 60-POUNDER GUN MATERIEL (BRITISH). The United States procured a number of batteries of 5-inch, 60 pounder guns with the necessary accompanying vehicles from Great Britain. The materiel is of British design and manufacture throughout, and the units ceded to the United States include the gun, Mark I, mounted on a carriage, Mark II ; the gun carriage limber, Mark II, the ammunition wagon, Mark II ; and the ammunition wagon limber, Mark II. The materiel was originally designed for horse transportation and thus is provided with poles and the necessary attachments for horse REAR LEFT VIEW OF CARRIAGE IN BATTERY. draft. By substituting the engine-draft connector in place of the horse- draft poles, the materiel is converted into motorized batteries and may be drawn by tractors. When horse drawn, it is customary to divide the four vehicles into two trains, each having two vehi- cles ; however, when the battery is adapted for motor draft, the four vehicles are drawn as one train. The load of the gun carriage and limber is about as heavy as is practicable for horse transportation, although the British originally designed their 8-inch howitzer materiel, which is of greater weight, for horse transportation. The carriage is of the constant recoil type, the recoil mechanism being of the hydrospring type, located above the gun. The recoil mechanism consists of two spring cylinders and one hydraulic cylinder filled with glycerine and water. The piston rod of the recoil cylinder and the rods of the two spring cylinders are connected to the lug on the breech ring of the gun and therefore recoil with the gun. (209) H 210 5 x I I 211 Upon recoil of the gun, the liquid is forced past the piston head through a throttling groove or slot cut in the wall of the cylinder. The resistance offered by the action of the liquid in the cylinder, together with the resistance offered by the compression of the springs in the cylinders, controls and absorbs the shock of recoil, permitting the carriage to remain practically stationary upon the ground when the piece is fired. The energy stored up in the spring cylinders due to the compres- sion of the springs during recoil is sufficient to cause the gun to re- turn to the firing position. A hydraulic counterrecoil buffer is provided at the front of the hydraulic cylinder and acts as a cushion, thereby preventing the violent return of the gun to firing position. VIEW SHOWING TRAIL CONNECTED TO LIMBER. A range of 12,280 yards (11,230 meters) is possible, when firing a 60-pound projectile with a muzzle velocity of 2,080 feet per second at the maximum elevation of 21. The carriage is equipped with tractor wheels provided with inde- pendent wheel brakes. The trail is of the single unit type, being broadened at the spade end and equipped with a fixed spade for anchoring the trail to the ground. When traveling, the carriage is connected to the limber by an adjustable connecter. The carriage permits elevation from 5 depression to 21 eleva- tion. The carriage permits traverse of 4 left and 4 right, when it is elevated at 16^ or less. At higher elevations the traverse is but 3 right and 3 left, due to the interference of the trail with the gun at these elevations. 212 Weights, dimensions, and ballistics. Weight of carriage and gun pounds 12, 096 Weight of gun and breech mechanism do 4, 858 Weight of carriage do 7, 238 Weight of projectile do GO Weight of powder charge do 9. 44 Pressure of trail on ground do 920 Length of gun inches 168. 05 Length, over all, of carriage and limber, traveling position, with gun but without limber pole feet 28. 625 Length, over all, of carriage and limber, traveling position, with gun and pole feet 37^6 Length between axles, of carriage and limber, traveling position do 13. 75 Height of axis of gun from ground inches 51. 5 Maximum elevation degrees 21. 5 Maximum depression _, do 5 Traverse (at elevation of 16 J or less) : Degrees right 4 Degrees left 4 Traverse (at elevation above 16^) : Degrees right 3 Degrees left 3 Range, maximum yards 12, 280 Muzzle velocity, normal ft. per sec 2, 080 Rifling, uniform 1 turn in 30 calibers. Diameter of carriage wheels inches 60 Track, center line to center line of wheels do 63. 5 Diameter of turning circle feet 54 5-INCH, 60-POUNDER GUN, MARK I, AND CARRIAGE, MARK II (BRITISH). The gun is of the wire wound type and consists of two tubes, jackets, breech bush, breech ring, and several layers of steel wire. The inner tube extends the length of the barrel, the outer tube being shrunk upon it, extending over the rear of the inner tube to form a threaded bearing for the breech bush which receives the breech block. The jacket is fitted over the tubes and extends to the rear, having a threaded section on which the breech ring is received. Several layers of steel wire are interposed between the jacket and tubes, the jacket being shrunk over the wire. The breech ring is provided at the top with a lug, to whicji the recoil piston rod and the rods of the spring cylinders are secured, being the direct connection between the gun and recoil mechanism, and is provided with lugs at the right side which accommodate the breech carrier. On either side of the jacket longitudinal projections are provided, which engage and slide in corresponding slots in the cradle. The breech block is of the interrupted screw type, having threaded and slotted sectors. The breech bushing is threaded and recessed to correspond with the sectors on the breech block. The breech mechanism is so arranged that by one pull of the breech lever from left to right the breech screw is unlocked and the screw and carrier swung into loading position. After loading, one thrust of the same lever inserts the breech screw into position in the breech bush and turns it into the locked position. The breech screw is supported by the carrier, which pivots and is hinged to the lugs provided on the right side of the breech ring. The firing mechanism is of the " T " type and is fitted with a safety device which prohibits the firing of the gun until the breech is closed. Discharge is by means of a lanyard operated from the right side of the carriage. The carriage consists of the following major parts : Cradle, includ- ing recoil mechanism ; top carriage ; elevating and traversing mech- anisms ; trail ; brake gear ; wheels and axle. The carriage is constructed on the long recoil principle, having practically a constant length of recoil at all elevations. The length of recoil is approximately 57 inches. The recoil mechanism is placed parallel with, and located above the gun, the gun sliding during recoil and counterrecoil in slides provided in the cradle. (213) 214 The recoil mechanism being of the hydro-spring type, utilizes two spring cylinders and one hydraulic cylinder, independent of each other, and held in relative position by the cradle. The cradle is cylindrical in form and inclosed the breech end of the gun, and is provided with threaded holes at the front and rear for the reception of the spring and hydraulic cylinders, which are screwed into these holes. The three cylinders extend to the rear and engage suitable holes in the breech ring to which they are fastened by connecting pieces, the two spring cylinder rods being retained by nuts, and the hydraulic cylinder rod by an externally threaded collar which passes through the breech ring and engages the thread on the piston rod, the three rods recoiling to the rear with the gun. The trunnions of the cradle are received in bearings in the top car- riage, which in turn is pivoted on the front end of the trail to permit traverse. REAR RIGHT VIEW OF CARRIAGE. Traverse and elevation is accomplished through the medium of handwheels located on the left side of the carriage. The elevating handwheel actuates a pinion meshing with a rack bolted to the cradle. The traversing handwheel operates a screw, one end of which is hinged on the top carriage, the other end engaging a nut which pivots on the trail. Traversing stops are provided on either side of the top carriage to limit the traverse to 4 right and 4 left, when the gun is elevated at 16 or less. The amount of traverse is indicated by a pointer fixed to the trail, which reads to a graduated scale on the rear transom of the carriage. The trail is of the solid type, being cut out at the front to give clearance to the breech of the gun during recoil, and at high eleva- tions. The front end of the trail is equipped with bronze brackets through which the axle passes. The trail has a bearing at the 215 forward section on which the top carriage rests and pivots, and through which the pivot pin passes, retaining the top carriage in proper position. Clips are provided on the trail which engage pro- trusions on the top carriage, preventing vertical movement of the top carriage when the gun is fired. Traversing stops are provided to prohibit traversing of more than 3 left and 3 right, when the gun is elevated above 16. The rear end of the trail is equipped with a connector for limber- ing the carriage to the carriage limber. The connection is held in position by pins, and is provided with holes for adjustment. A spade of the fixed type is riveted to the rear end, and holds the trail in a practically stationary position when the gun is in action. A traveling lock is provided on the trail which engages the breech of the gun at degree elevation, when traveling. The lock is hinged to the inside of the trail members and swings down when the gun is in firing position. The wheels are of the tractor type, being provided with diagonal cleats riveted to the rims. The wheels are 60 inches in diameter and have tires 12 inches in width. A "brake ring is provided on each wheel against which an internal brake shoe is fitted, which is operated by a handwheel at the front of the carriage. Sighting is accomplished by means of a tangent sight and foresight on the right side of the carriage, and by an oscillating sight and dial sight (panoramic sight) on the left side of the carriage. The tangent and foresight together form an open sight for the direct laying of the gun. The oscillating sight on which the dial sight is mounted is used for indirect laying; the oscillating sight being used for laying in elevation and the dial sight for direction. Ammunition of the separate loading type is used, being both ex- plosive shell and shrapnel. The weight of each is 60 pounds. The propelling charge consists of 9 pounds 7 ounces of cordite. Nor- mally these charges are not separate for zone fire, although special charges are sometimes made up for this purpose. 5-INCH, 60-POUNDER, GUN CARRIAGE LIMBER, MARK II (BRITISH). The limber consists mainly of a steel frame, two steel chests, wheels, axle, and draft connections. The vehicle is designed for 2-horse, 4-horse, or tractor draft. When horse drawn, the front end of the frame is equipped with a wooden horse pole, which is retained in place by a pin passing vertically through the rail and pole, and is also equipped with two or four singletrees, as the draft may require. Chains, with the necessary draft connections, are also provided, and extend from two points on the frame to the forward section of the pole, thereby adapting the vehicle for additional horse draft. The necessary neck yoke bars are provided on the draft pole. FRONT VIEW OF CARRIAGE LIMBER. For 4-horse draft, the two outside singletrees are suspended from outriggers which are hinged to the main frame, and are steadied by stays extending back to the axle arms. For 2-horse draft, the two outside singletrees are removed, the stays disconnected, and the outriggers folded back and over the main frame, being held in the latter position by straps. The singletrees, when removed, are strapped across the center of the frame forward of the steel chests. For tractor draft, all the singletrees are removed and strapped to the frame, the horse pole being removed and replaced by the motor draft connector which is pinned to the frame. (216) 217 The frame consists principally of four side rails, two inner and two outer, connected at the rear to the axle by flanges and pins. The front end is joined together by connecting plates, the frame being strengthened by diagonal stays. In th rear of the frame at the center, a pintle is provided, which accommodates the adjustable connector on the trail of the carriage in traveling position. The pintle is provided with a thumb latch which prevents accidental unlimbering of the trial connector. The steel chests are riveted to the main frame at the rear, on either side. The inner rear corners of these chests are formed diagonally REAR VIEW OF CARRIAGE LIMBER. to allow clearance to the swing of the connector on the carriage, when traveling. The chests are of flanged steel, having lift lids which are hinged at the front side and are equipped with hasps, locks, and chains at the rear. The interior of each chest is fitted for carrying stores, and each is provided at the top with a tray which carries small stores. The left chest is constructed to carry the sights and attachments, together with a number of small tools, and one powder charge in a tin box. The right chest carries the clinometer, oil can, and other various tools and accessories, together with one powder charge in a tin box. Extending from the base of each chest toward the rear a steel bracket is provided on which one round of ammunition is carried. 218 The shell is held in a vertical position on this support by a bronze bracket and a strap. Suspended below the frame at the rear, a wire net tray is provided for carrying drag ropes and lashings. Forward of the steel chests, on the top of the frame, a board is fastened, extending across the frame, and is equipped with friction clips for the accommodation of two rifles. The wheels provided are 60 inches in diameter, having steel tires 6 inches in width. The outer end of the axle arms are equipped with drag washers to assist hauling. No brakes are provided on this vehicle. Weights, dimensions, etc. Weight without two projectiles 1 pounds 2, 240 Weight on limber pintle, traveling position do 641 Weight on pole, carriage limber (at center tug hole) : Without two projectiles do 51 With two projectiles do 39 Diameter of wheels inches 60 Track of wheels, center line to center line do 63. 5 Length : With horse pole do 186 Without horse pole do 77 Width : Over axle with dust caps do 78. 5 Outriggers extended do 110 Outriggers folded do 65 5-INCH, 60-POUNDER, AMMUNITION WAGON, MARK II (BRITISH). The ammunition wagon (caisson) consists principally of a steel frame, ammunition chest, fuze lockers, brake gear, draft fittings, wheels, and axle. The wagon is constructed to carry 24 rounds of ammunition, 24 powder charges in tin containers, and 2 fuze boxes. The exterior is fitted with fastenings to carry ropes, handspikes, also other tools and accessories. FRONT VIEW OF AMMUNITION WAGON. The ammunition chest is constructed of flange steel, having flange steel brackets on either side at the center, which extend below the chest, providing bearings which receive the axle. The interior of the chest is divided into a front section and a rear section, by a vertical steel plate passing through the chest parallel to the axle. Each section is divided by steel plates passing crosswise through the chest into three horizontal rows of compartments. The lower compartments contain 4 high-explosive shell and 4 shrapnel. The middle row contains 2 high-explosive shell, 2 shrapnel, 2 powder charges in tin containers, 1 fuze box containing 14 fuzes, and 1 empty compartment. The upper row of compartments contain 10 powder charges in tin containers. (219) 220 The powder charge containers, and the shell are retained in the proper position by quick release straps, and the shell are withdrawn from their respective compartments by means of the packing blocks which inclose the nose of the shell, and by the withdrawing straps provided. The withdrawing straps extend the length of the shell and are fastened to the nose blocks, and are also rivited to the com- partment plates, preventing their complete removal. When the shell is withdrawn about half its length, the withdrawing strap is slipped over the base of shell allowing the complete removal of the REAR VIEW OF AMMUNITION WAGON. shell, while the packing blocks and straps are held in their respective compartments. The powder charge containers can be lifted out with- out the aid of straps. The front compartment is equipped with a steel door which is hinged at the bottom and swings downward when opened. The rear compartment is equipped with an armor-plate door hinged at its lower edge, and when opened hangs vertically downward. The front door when opened downward is supported by the footboard in a horizontal position. Each door when closed is held in position by latches provided on the sides of the chests, which swing over and engage steel handgrips riveted on either edge of the door at the top. 221 Extending above the chest at the front on either side, handrails are provided. The rails are constructed of steel and are provided with leather guards. The rails fit into small brackets rivited to the chest sides, and may be dismounted from the chest by removing the retaining pins. Three grip straps are also fastened to the upper front edge of the chest to assist the personnel when mounting the vehicle. Straps are provided with the usual fastenings at the top of the chest to accommodate the soldiers' personal equipment, and also picket ropes at the rear. At the front of the chest the fastenings accommo- date blankets, lamps, and tool cases. On either side of the chest fastenings are provided, the left side accommodating a saw in a leather case, and the right side a spanner wrench. The frame consists of two flanged sides connected by cross stays to the draft pole, which consists of two flange steel members extending back the length of the vehicle. The outside rails are provided with flanges and holes through which the axle passes. The chest is mounted on the frame, the axle brackets on the chest corresponding with the flanges on the side rails, making a solid bearing for the axle, which is held in place by keys. Forward of the chest, across the side rails, a wooden footboard and platform is provided. Suspended below the footboard on either side is a fuze locker, which provides carrying compartments for 30 fuzes, 15 in each locker. Each locker is provided with a door, which swings downward when opened, and each is equipped with a hasp and a pivot thumb lock. Suspended from the platform to the rear of the right fuze locker, a tin box, containing 3 pounds of grease, is strapped. The frame is provided at the rear with a steel prop which swings up to the right side of the frame and is retained in this position by a spring clip when in traveling position. Wire-net receptacles are suspended under the rear section of the frame on either side of the prop bracket. The receptacles provide space for canvas watering buckets and ropes. The draft pole, which is an extension of the center rail of the frame, is joined at its extreme forward end by a lunette, which engages the pintle on the ammunition wagon limber when in traveling posi- tion. A pole prop is also provided for supporting the draft pole when the wagon is unlimbered. The prop swings up to a horizontal position when the wagon is in traveling position. Attachments on the underside support a jointed draft pole and a handspike. Tire brakes are provided for each wheel, the brake system being operated as one unit. The shoes which bear against the wheel are supported by brackets fastened to the side rails at the front. 222 The shoes are operated by a crank located on the left rear side of the vehicle under the frame. The crank is connected to the shoes by rods supported on the frame. Wheels of the wooden type, 56 inches in diameter, having steel tires 3 inches in width, are provided on this vehicle. They are retained on the axle by means of an adjusting collar and linch pin. The bearing is protected from dirt and other foreign matter by a dust cap which fastens over the end of the hub box. AMMUNITION WAGON AND AMMUNITION WAGON LIMBER. LIMBERED. Drag washers are provided on each wheel to which ropes may be fastened to assist in the maneuvering of the vehicle. Weights, dimensions, etc. Weight of wagon, empty pounds-- 1, 732 Weight of wagon, loaded and equipped do 3, 556 Pressure of wagon pole on limber pintle, loaded do Pressure of wagon pole on limber pintle with two men on wagon, loaded pounds 196 Height to top of handrail feet 5. 229 Height, handrails removed do 4. 416 Width, maximum do 6. 291 Length of wagon : do _ 9. 708 Greatest projection beyond track of wheels . inches 6. 25 Wheel track do 63 Diameter of wheels do 56 5-INCH, 60-POUNDER, AMMUNITION WAGON LIMBER, MARK II (BRITISH). The limber comprises the frame with pintle; ammunition chest; fuze locker; draft fittings; wheels and axle. The limber is designed to draw the ammunition wagon by means of the pintle provided at the rear. The vehicle is equipped for 2-horse draft. It carries 16 rounds of ammunition together with the necessary powder charges. Provision is also made to carry 43 fuzes. 28 of which are carried in the ammunition chest, and the remainder in the fuze locker fastened to the top of the chest. Imple- ment fastenings are fastened on the exterior of the chest and foot- FRONT VIEW OF AMMUNITION WAGON LIMBER. board, and accommodate rifles, blankets, and the customary tools and accessories. The chest is constructed of steel and is provided at the rear with three doors. The interior of the chest- is subdivided by two steel plates into three main divisions, access to each being at the rear. Each division is separated by cross plates into four rows of com- partments, the lower two rows of each division being subdivided into smaller compartments to accommodate a total of eight high ex- plosive and eight shrapnel shells. 5516021 1 r, ( _>_>:} ) 224 The two upper rows of the two outside divisions are constructed to accommodate a total of 16 powder charges, each protected by tin containers. The two upper rows of compartments in the middle division accom- modate a tray for small stores, such as cotton waste, pins, pliers, and other small tools; and 2 fuze boxes, each containing 14 fuzes. The fuze boxes occupy the upper row of compartments. The powder-charge containers and the shell are retained in place in the chest by quick-release straps, and the shells are withdrawn REAR VIEW OF AMMUNITION WAGON LIMBER. from the compartments by withdrawing straps and blocks, identical with those on the ammunition wagon. A door is provided at the rear of the chest for each main com- partment. The two outer doors are of armor plate and have hinges at the bottom edges, and when opened hang down vertically from the chest. A small armor-plate apron is hinged to each door at its upper edge. The aprons hang vertically from the door when each door is opened, and form an extension toward the ground, thereby giving additional protection for the personnel serving the gun. When the door is in closed position, the aprons fold down over the outside of the door and are retained in position by latches fastened 225 to the upper part of the chest, which engage steel hand grips riveted to the aprons. The middle compartment is equipped with a steel door which is hinged at the upper edge, and when opened, rests over the top of the chest. The spring latches with thumb lift grips are riveted to the door which engages suitable latches on the lower edge of the chest when the door is in the closed position. Two small clips which extend over the edge of the side, at the lower sides, act as retainers for the outer odors when they are closed. In operation the middle door is first opened, thereby removing the clips which bear against the outside doors, allowing the outer doors to be swung open. In closing the chest the two outer doors are closed first. Handrails, protected by leather, are provided on either side of the chest, and extend above the chest. They engage suitable brackets riveted to the chest, to which they are fastened by pins. By the removal of the retaining pins, the handrails may be dismounted from the chest. The exterior of the chest is fitted with implement fastenings and straps, the front plate having spring catches for three rifles. Three grip straps are fastened to the upper edge of the chest at the front, to assist the personnel in riding on this vehicle. Three leather pockets, one on the rear middle door and one on either side of the chest, are provided for carrying fuze and limber keys. A wooden locker for carrying fuzes is fastened by steel straps to the top of the chest on the left side. The locker is equipped with a lift lid, hinged at the front and provided with a hasp and thumb lock at the front. The interior is constructed to carry 15 fuzes. Two blankets, which serve as a seat cushion, are strapped to the top of the chest at the front, and the soldiers' personal equipment is strapped at the rear. Each side of the chest has riveted thereto a steel bracket, which extends below the chest body, and is provided with an opening through which the axle passes. The frame which supports the ammunition chest consists mainly of two side rails, two middle rails, and the connecting cross rails. The middle rails are connected at the front of the frame to form a seat for the wooden horse pole. The outer rails converge slightly at the front, and with the middle rails form a support for the wooden platform and footboard. Two of the cross rails extend across the frame, directly beneath the edges of the chest, giving a solid support to which the chest is fastened. The other cross rail extends across the extreme front of the frame and is fitted with hooks for the sup- port of two singletrees. A wooden horse pole, equipped with a neck yoke bar, is provided. 226 Forward of the chest a wooden footboard and platform is fastened to the upper side of the frame. The boards have staples for the accommodation of leather straps, which secure rope lashings, shovels, and other similar equipment to the footboards. On the under forward right side of the frame a case is provided to carry a bolo. On the left side of the frame, in a corresponding posi- tion, a case is provided to carry a water brush. Suspended from under the wooden platform, on the left side, is a box containing 3 pounds of grease. Under the right side of the platform, fastenings are provided to carry two cans containing lubri- cating oil. A pintle, which engages the lunette on the draft pole of the ammu- nition wagon, is provided in the frame at the rear. In each side rail at the rear a hole is provided which forms a bear- ing for the axle. The steel axle bracket on the sides of the chest correspond with these holes, and form a solid bearing for the axle, which is held in place by keys. Wheels of the wooden type, 56 inches in diameter, having steel tires 3 inches in width, are provided. An adjusting collar and linchpin screws the wheel to the axle. Protection against the ingress of dirt and foreign matter is provided by a dust cap which fastens over the end of the hub box. Drag washers to assist in the maneuvering of the vehicle are pro- vided on each wheel. The wheels and axle of the limber are interchangeable with those on the ammunition wagon. No brake is provided on the ammunition wagon limber. Weights, dimensions, etc. Weight of limber, empty -.pounds 1, 410 Weight of limber, loaded and equipped do 2,632 Weight of wagon and limber, empty do__ 3, 148 Weight of wagon and limber, loaded do 6,188 Weight of limber only, with wagon limbered up, empty do 1. 486 Weight of limber only, with wagon limbered up, loaded do 2, 730 Weight of limber pole at position of center tug hole with wagon limbered up, loaded, without men pounds 14 Weight of limber pole at position of center tug hole with wagon limbered up, loaded, with 2 men on limber only pounds Weight of limber pole at position of center tug hole with wagon limbered up, with 2 men on limber and; 2 men on wagon pounds 25 Length of limber with pole feet__ 14. 166 Length of limber without pole do 5. 5 Length of limber and wagon, over all do 22. 687 Length between axles of limber and wagon do 8. 25 Height of limber to top of handrails do__ 5. 666 Height of limber, handrails removed do 4. 895 Width of limber, maximum do 6.291 Wheel track of limber inches 63 Diameter of wheels of limber do 56 Diameter of turning circle of limber and wagon feet 23. 5 155-MILLIMETER .HOWITZER MATERIEL, MODEL OF 1917 (SCHNEIDER). Experience indicated the necessity of artillery of larger caliber than the 75-millimeter, having a longer range and better character- istics, yet mobile enough to permit its use as a supplementary weapon. This necessitj- led to the adoption of the 155-millimeter caliber, as the more suitable 105-millimeter caliber was not available then. The importance of this 155-millimeter howitzer is evident when it is realized that it is the largest weapon at the present time that can be used by combat divisions, and is especially valuable for use against strongly intrenched infantry and in counter battery firing. The type of 155-millimeter howitzer carriage adopted is known by the French as the 155-millimeter Court Schneider, model of 1917, and by the United States as the 155-millimeter howitzer carriage, model of 1918 (Schneider). The howitzers manufactured in the United States RIGHT SIDE VIEW OF CARRIAGE IN TRAVELING POSITION. are also distinguished from those made in France by the designation ''Model of 1918." The American materiel differs from the French in having a straight shield instead of a curved one, rubber instead of steel tires, a slightly different firing mechanism, and several other minor changes. The howitzer is mounted on a carriage having a single trail composed of two pressed steel flasks. At the front end these are connected by the axle housing and at the rear by a fixed spade. The carriage embodies many ingenious features designed to reduce the weight and insure stability. The recoil mechanism is of the hydropneumatic type, the sleigh recoiling with the howitzer. In recoiling the liquid is forced from one side of the piston to the other through a variable orifice, which gradu- ally closes until the howitzer is brought to a stop. The return of (227) 228 229 the howitzer into battery is effected by the expansion of the air com- pressed during recoil. The length of recoil is practically constant, and in order to allow the howitzer to be fired at high elevations without digging in the trail the trail is made of a curved shape. FRONT VIEW OF CARRIAGE IN BATTERY. By sliding transversely along its axle the howitzer is capable of traversing through a total angle of 6. Its maximum elevation is approximately 42. It fires a 95-pound projectile with a muzzle velocity of about 1,480 feet per second to a maximum range of about 12,300 yards. Separate loading ammunition is employed. By the use of the reduced powder charges, shorter ranges are reached with SIDE VIEW OF CARRIAGE EN ROUTE. steep angles of fall and with less wear on the gun. Its life, before relining is necessary, is approximately 7.000 rounds. The entire equipment is horse-drawn and the equipment for each howitzer includes a carriage limber, used when traveling to support the trail, three caissons or ammunition vehicles, and a number of repair and supply trucks. 230 155-MILLIMETER HOWITZER MATERIEL, MODEL OF 1918 (SCHNEIDER). The 155-millimeter howitzer, model of 1918 (Schneider), is of the hydropneumatic long-recoil type, which may be used for direct fire, but was specially designed for indirect fire. On account of its high trajectory it is able to direct shells on targets inaccessible to field guns of limited elevation. This howitzer has given satisfactory results in actual service and has proven to be superior to other howitzers of similar caliber. It has a muzzle velocity of 1.480 feet per second and attains a maximum range of 12,300 yards, the projectile weighing approximately 95 pounds. A maximum rate of fire of four rounds per minute may be attained, but heating as well as difficulty of preparing and serving of ammuni- tion by the gun crew renders such rate impossible for any length of time, however. The normal rate of fire is two per minute. The howitzer is mounted on a sleigh and rigidly secured by a breech key and a holding-down band. The sleigh contains the recoil mechanism which permits long recoil and insures stability at low elevations. When the gun is fired, the sleigh recoils on bronze slides on the cradle, which is a U-shaped steel plate and rests on the trunnion bearing of the trail. This howitzer may be elevated from zero to 42 by means of the elevating mechanism. The traverse is 52.5 mils to the right and left, the carriage sliding on the axle and pivoting on the spade, which prevents the carriage from recoiling when the gun is fired. The customary shield affords protection for the gunners from shrapnel and flying fragments. In traveling position the howitzer is retracted and locked to the cradle, the cradle locked to the trail, and the spade revolved and se- cured to the bottom of the trail. The lower end of the trail rests on the carriage limber, which is used to carry its proportionate share of the load of the howitzer and carriage in traveling position. The limber is equipped with a connecting pole for motor traction. The carriage and limber wheels are rubber tired and considered able to travel over any roads suitable for field artillery. This materiel consists of: The 155-millimeter howitzer and carriage, model of 1918 (Schneider). The 155-millimeter howitzer carriage limber, model of 1918 (Schneider). The 155-millimeter howitzer caisson, model of 1918. (231) 232 g _l iL i! 233 The howitzer, carriage, and limBer are of French design and were manufactured in the United States. The caisson is of American design and manufacture. This materiel is used with motorized batteries, and a full complement of tractors and trucks is provided for the transportation and service of the battery. The cart, model of 1918, and reel, model of 1909 MI, described with the 75-millimeter materiel, are also used with this materiel. Weights, dimensions, ballistics, etc. Weight of howitzer, including breech mechanism pounds 2,690 Caliber inches 6.10 Total length do 91. Weight of projectile pounds 95 Weight of maximum powder charge do 8 Muzzle velocity of shell feet per second 1,476 Muzzle velocity of shrapnel : Minimum do 666 Maximum do 1, 434 Maximum range of shell yards 12,250 Maximum range of shrapnel do 10,700 Weight of howitzer and carriage, fully equipped pounds 7,600 Weight of carriage complete, but without equipment do 4, 729 Diameter of carriage wheels inches 53 Width of carriage track do 60 Normal length of recoil do 51. 30 Elevation to 42 20 Maximum traverse 3 (52$ mils) right and 3 (52$ mils) left. Weight of limber, completely equipped pounds 1, 440 Diameter of limber wheels inches 42. 82 Width of limber track do 61 Turning angle of 155-millimeter howitzer, limber and carriage limbered degrees 52 234 Vs a s / ' i 2 Y ' , c s 'i ! \ i Mi I i 235 155-MILLIMETER HOWITZER AND CARRIAGE, MODEL OF 1918 (SCHNEIDER). The howitzer is of the built-up type and consists of a tube hav- ing a jacket shrunk over its rear half. The breech end is equipped with a counterweight which is fitted with leveling plates to be used with a gunner's quadrant when setting elevations. Below the breech recess is the bridle which couples the gun to the sleigh and on the forward end of the howitzer a holding down band also functions to secure the tube to the sleigh. The breech mechanism is of the plastic obturator type with an interrupted screw type breechblock. The breechblock is hinged at the right and by means of one motion of the breech lever can be ro- tated and swung clear of the breech. The forward mushroom-shaped head of the breechblock is equipped with a flexible asbestos ring known as the obturator pad. The gas check pad or plastic obturator is composed of a mixture of one part asbestos and three parts nonfluid oil, contained in a canvas cover- ing. The pad is protected by the small, front, and rear split rings. A steel filling-in disk is placed between the gas check pad and the breechblock. On firing, the asbestos ring is compressed and acts as a gas check to prevent the leakage of powder gases back through the breech. The asbestos pad, by its shape, causes the split rings to spread when pressure is applied on the mushroom head. It has sufficient resiliency to resume its original form after firing. The firing mechanism is of the French percussion primer type. The primer is fired by means of the firing pin driven forward by a hammer operated by the lanyard. The firing pin is supported in the firing mechanism block, which is unscrewed each time a new primer is inserted. A safety device is used in connection with the firing mechanism block, which makes it impossible to unlock the breech while the block is in position, or to insert the block while the breech is unlocked. The firing mechanism block is interchangeable with those used in the following weapons: 155-millimeter gun, model of 1918 (Filloux). 8-inch howitzer (Vickers Mark VI and VIIIJ). 240-millimeter howitzer, model of 1918 (Schneider). The recoil mechanism is of the hydropneumatic long recoil type. With this howitzer the type of recoil is known as constant, i. e., the length of recoil is not shortened at high elevations. The sleigh contains the recoil mechanisms and serves as a support for the (236) 237 238 239 howitzer, being secured to it by the breech lug and the holding down band. On recoiling, howitzer and sleigh move on the cradle fastened to the trunnions of the carriage, the piston rods remaining stationary. A mixture of glycerine, water, and caustic soda is used in the recoil brake and counterrecoil mechanism. The gas used in the counterrecoil mechanism may be either air or nitrogen. Nitrogen is always used when available, as it has no corrosive action on the mechanism. The energy of recoil is absorbed by the friction of the liquid while passing through the openings in and around the recoil piston and by the compression of the nitrogen in the cylinders. The howitzer is returned to battery by the energy stored in the compressed nitrogen which forces the liquid out and reacts against the counterrecoil piston. When in battery, the initial nitrogen pressure is approximately 485 pounds per square inch, which is sufficient to hold the howitzer in battery at all angles of elevation. Gages are provided to indicate both the quantity of liquid and the nitrogen pressure. Suitable pumps are provided with the materiel for pumping in liquid and air. Cylinders of compressed nitrogen are carried to replenish the supply of nitrogen. The cradle is secured in the trunnions of the carriage and supports the sleigh during recoil. To the underside of the cradle are fastened two elevating arcs by which the howitzer is elevated by means of the handwheel located on the left side of the carriage. Elevations from O c to 42 20' may be obtained. The traverse of the carriage is obtained by the traversing mech- anism causing the carriage to slide on the axle, the trail pivoting on the spade. The movement is 3 each side of the center, or a total of 105 mils. The movement is obtained by means of a traversing nut rigidly fastened to the axle, causing a traversing screw to travel carrying the carriage along the axle. The carriage travels along the axle on rollers mounted on Belleville springs. When the gun is fired, the springs are compressed and the carriage rests on the axle. A lock is provided for relieving the strain on the traversing and elevating mechanisms when traveling. Two traversing handwheels are provided, one on each side of the carriage. The wheels are of wood, 1,350 millimeters (53 inches) in diameter and are fitted with solid rubber tires. The carriage is equipped with a pair of brakes acting directly on the rubber tires. An armor- plate shield for the protection of the personnel against small arms and shrapnel fire is also provided. Sighting is accomplished by means of a quadrant sight, panoramic sight, and peep sight. 5516021 16 240 241 242 The quadrant sight, model of 1918 (Schneider), is mounted on the left trunnion of the carriage. It is used for laying the piece in elevation. The angle of site mechanism is combined with this sight. Mounted on the top of the quadrant sight is the United States pano- ramic sight for laying the piece in traverse. An extension bar is provided for use with the panoramic sight to enable the sight to be raised enough to see over the shield or other obstructions in direct aiming. The peep sight, used only in direct fire, or in emergency, may be mounted on the quadrant sight in place of the panoramic sight. Two complete sets of night sighting equipment are provided for use when firing at night. When not in use these equipments are packed in cases provided for that purpose and carried on the carriage limber. The night lighting equipment consists principally of a chest, an aiming lamp, an azimuth lamp, a portable lamp, and the necessary cables and fixtures. 155-MILLIMETER HOWITZER CARRIAGE LIMBER, MODEL OF 1918 (SCHNEIDER). The 155-millimeter howitzer carriage limber is a two-wheeled vehicle employed to support the trail of the carriage when traveling. This limber consists of a built-up steel frame mounted on wheels and axle. It has no chests and provides no seats for the personnel. The pintle is riveted to the extreme rear end of the frame and serves as a bearing for the lunette of the carriage when the howitzer is limbered. Additional support for the trail is provided by a trail rest riveted in front of the pintle and on which the fifth wheel of the trail bears. Hooks are provided for carrying a picket rope, and small boxes for carrying grease and the night lighting equipment are secured on the frame. A prop is provided on the front of the frame for holding the limber up when not en route. The standard short pole with the lunette for motor traction batteries is provided, or the long pole may be substituted for horse-drawn equipment. The wheels are of wood construction, 1,240 millimeters (48.82 inches) in diameter, with solid rubber tires. Weight and principal dimensions. Weight of limber empty pounds__ 1, 227 Weight of limber completely equipped do 1,440 Weight of limber and carriage, limbered _do 8, 930 Weight on ground under each wheel, with carriage limbered do 1, 380 Weight of each wheel \lo 335 Diameter of wheels inches 48.82 Width of track do 61 Turning angle of limber and howitzer carriage, limbered degrees 52 NOTE. The weight of this carriage limber equipped with horse pole is prac- tically the same as with motor pole. (243) 244 TREE OWH EYE LONGITUDINAL SUPPORT OMTR/IL SUPPORT AUXILIARY BRACKET TUOm. SUPPORT TEBAR SAFETY CHAIM 5ATETY CHAJM CROSS BAR PLATE. PLATE CASE TOANSVtRSE SUPPORT 155 MM. HOWITZER CARRIAGE LIMBER. MODEL OF 1918 (SCHNEIDER). PLAN AND RIGHT SIDE VIEWS I00200.W0400500600W0800TOIOOOIIOO 1200 1500 MOO MLUMETER5 155-MILLIMETER HOWITZER CAISSON, MODEL OF 1918. The 155-millimeter howitzer caisson is a two-wheeled, spring- supported vehicle for the transportation of ammunition. Normally it is a motorized vehicle, two caissons forming a train drawn by one tractor. However, by removing the connecting pole and substitut- ing the standard pole the front vehicle of the train can be converted into a horse-drawn caisson limber. Any caisson in the battery REAR VIEW OF CAISSON. except the caisson equipped with the hand reel can be so converted into a caisson limber. The caisson carries 14 complete rounds of ammunition and 2 extra powder charges for the 155-millimeter howitzer. The chest is made up of the lower and upper chest body and rear plate, which is of armor plate. The chest is divided into an upper and lower compartment, the opening between them forming a space for the axle, pole socket, and pintle bracket, and houses the fuze box and oil can. The upper compartment is arranged for the transportation of 8 projectiles and 16 powder charges. Powder is served to the caissons in fiber containers, each containing 2 powder charges. The (245) 246 247 container is fitted with an air-tight-joint metal cover and base. The lower compartment is arranged for the transportation of 6 projectiles. The upper chest door when closed forms a cover for the chest and is held open by door props. When open, this armor plate door serves as a shield for the cannoneers. The lower compartment is also provided with an armor plate door hinged to the bottom of the chest body, and has an armor plate apron hinged to its edge. When open, the lower chest door and apron hang down, forming a shield for the cannoneers. When closed, this door forms a cover for the lower compartment ; the apron doubles back against the lower chest door and is latched in place. Both compartments are provided with loose diaphragms, by the use of which the caisson can be made available for transporting any of the following types of shells : 155-millimeter common steel shell, Mark I; 155-millimeter common steel shell, Mark II; 155-millimeter shrapnel, Mark I ; 155-millimeter common steel shell. Mark IV ; Semi-steel shell, Mark XVII. Only one type of shell can be carried in the same compartment at one time. When carrying either common steel, gas. or shrapnel, the loose diaphragms are placed in position after the projectiles are inserted in the projectile tubes. When the doors are closed (with either common steel or gas shells) the door stiffeners bear against the bases of the projectiles, holding them in place. With shrapnel the edges of the flanged holes in the loose diaphragm bear against the rotating bands of the projectiles. When used to transport com- mon steel shells Mark IV the loose diaphragms are placed inside the body of the caisson next to the front diaphragms. When the doors are closed the door stiffeners bear against the bases of the projectiles, holding them firmly against the loose diaphragms. Foot rests, handrails, and grip straps are provided on the chest for the convenience of its personnel. The outside of the chest is provided with implement fastenings for the usual complement of accompanying tools and accessories. Blanket straps are provided on top of the chest for carrying the blanket rolls of the battery person- nel ; provision also is made on top of the chest for carrying the con- necting pole and on the rear for carrying the lunette and caisson prop when used as a horse-drawn vehicle. The caisson prop when down serves to support the front end of the caisson ; in traveling it is swung up and held by the prop chain. The axle passes through the caisson between the upper and lower intermediate plates. Axle brackets are clamped on either end of the axle just outside of the chest, and rotation or lateral motion of the chest is prevented by clamp screws and Belleville springs. The chest 248 has a spring suspension similar to that of the 4.7-inch gun caisson, model of 1917, for lightening road shocks. The caisson is provided with a brake mechanism of the band type. The brake drums are mounted on the hub boxes of the wheels and the band brakes lined with Raybestos. A brake lever secured to a bracket riveted to the caisson body functions as a means by which the brakes may be applied. The caisson is usually equipped with the short pole for motor traction, but the pole socket is designed so that the long pole may be used when it is desired to use the vehicle as a horse-drawn limber. A FRONT VIEW OF CAISSON. standard pintle is fitted at the rear for the connection of the other vehicles. One caisson in each battery is equipped with a reel for caisson, model of 1917. This is a hand-operated reel for the transportation and handling of telephone wire. (See page 168.) Weights and Dimensions. Over-all length inchea 79 Over-all width do 78. 5 Over-all height do 67 Weight without equipment (unloaded) pounds 2,345 Weight fully equipped (unloaded) do 2,447 Weight completely equipped and loaded do 3, 949 Weight of reel caisson completely equipped and loaded do 4, 006 Width of track inches__ 60 Diameter of wheels do 60 Turning diameter of two caissons feet 18 155-MILLIMETER GUN MATERIEL, MODEL OF 1918 (FILLOUX). The type of 155-millimeter field gun adopted is known by the French as the "G. P. F." (Grande Puissance Filloux), and by the United States as the model of 1918. This caliber, which corresponds to 6-inch artillery, is the heaviest mobile artillery, exclusive of the heavy howitzers and the railroad artillery. This monster weapon is of rugged design, combining mobility and power, and has a large horizontal training angle to render it suitable for the concentration of artillery fire at long ranges. No other avail- able weapon of equivalent caliber can be considered to rival this type. TRAVELING POSITION (RIGHT SIDE). This piece is especially valuable in firing against captive balloons, counter battery firing, and interdiction. The Filloux gun is mounted on a carriage having a split trail of box girder section, which is spread out when in action, the ends of the trail being firmly anchored by spades in the ground. The split- trail effect permits clearance for recoil at high elevations and allows firing over a horizontal field of 60 and an elevation varying from to 35. Its muzzle velocity is about 2,411 feet per second, a rate of propul- sion that throws its projectile, weighing 95 pounds, approximately 17,700 yards, or a little more than 10 miles. The gun recoils in slides formed in the cradle which rests in the trunnions of the top carriage. The length of recoil is automatically controlled and varies with the elevation, while the counter recoil is pneumatic. The entire recoil mechanism is commonly called the recuperator and is supported on the carriage at its trunnions. When (249) 250 251 traveling, the trail is closed up and the ends thereof are supported by a carriage limber provided with a steering gear brake, and drawn^ by a tractor. In traveling position both carriage and carriage limber are supported on semielliptical springs to absorb all road shocks and vibrations. PREPARING CARRIAGE FOR BATTERY POSITION. The life of the gun before relining becomes necessary is about 3,000 rounds and maximum rate of fire is two rounds per minute. The entire equipment is motorized. A carriage limber, which sup- ports the trails in traveling, accompanies each gun. Caissons are not used with these guns, the ammunition being carried in motor trucks or cargo carriers. CARRIAGE IN TRAVELING POSITION (REAR VIEW). 155-millimeter gun materiel, model of 1918 (Filloux), consists of: 155-millimeter gun and carriage, model of 1918. 155-millimeter gun carriage limber, model of 1918. The above materiel is of French design and of both French and American manufacture. 252 253 Weights, dimensions, ballistic*, etc. Weight of gun, including breech mechanism pounds 8,795 Length of gun inches 232. 87 Caliber do 6. 1042 Muzzle velocity __feet per second 2,411 Rifling: One turn in 2,989 caliber, right hand, uniform. Weight of projectile pounds 95 Maximum range (Mark III shell at 39 elevation) yards 17,700 Weight of maximum powder charge pounds 25$ Weight of carriage only do 11,065 Weight of gun and carriage complete do 19,860 Diameter of wheels millimeters 1, 160 Width of track do 2, 250 Height of axis of gun from ground do 1, 482 Range of elevation degrees to 35 Maximum traverse do 60 Weight of gun carriage and limber pounds 23,050 Weight of limber complete do 3, 190 The distance from center line of carriage axle to center line of limber axle, approximately millimeters 4, 500 155-MILLIMETER GUN AND CARRIAGE, MODEL OF 1918 (FILLOUX). The gun, models of 1918 and 1918 MI, is of the built-up type, consisting of a tube strengthened by a ring, jackets, hoops, and the muzzle bell. All details except the firing mechanism provide interchangeability of parts with the 155-millimeter (G. P. F.) guns of French manufacture. A recoil lug on the under side of the breech ring provides means of attaching the recoil and recuperator rods. Bronze clips to serve as guides in the cradle are secured to the sides of the jackets. MAXIMUM ELEVATION OF GUN. The breechblock is of the interrupted- screw type, having four plain and four threaded sectors. The breech mechanism is of the plastic obturator type, having the forward mushroom-shaped head of the breechblock equipped with an asbestos ring known as the obturator pad. Upon firing, this ring is compressed and acts as a gas check to prevent the leakage of powder gases through the breech. It has sufficient resiliency to resume its original form after firing. The firing mechanism is of the French percussion primer type described under "155-millimeter Schneider howitzer," page 236, and is inter- changeable with the guns enumerated therein. The cradle is a steel forging bored with three parallel cylinders for housing the recoil brake and recuperator, and is pivoted by trunnions in the trunnion bearings of the top carriage. On the upper side of the cradle are slots for the gun slides, and to its lower side the elevat- ing rack is bolted. (254) 255 5516021 256 257 The recoil mechanism is of the hydropneumatic, variable recoil type. The larger of the three cylindrical bores in the cradle block contains the recoil mechanism; the two smaller ones, the parts of the recuperator mechanism. This mechanism consists of a piston and piston rod and a control rod. The piston rod is connected to the breech lug and, therefore, recoils with the gun. Grooves of variable depth are milled along the length of the control rod, controlling the flow of oil through the ports of the piston during recoil. The control rod assembles within the bore of the piston rod, and does not move longitudinally, but rotates. The amount of this rotating changes the area of the orifices through which the oil can pass. Its rotation is accomplished by means of an arm and gear sectors in such a manner as to shorten the recoil as the gun elevates. I CARRIAGE IN FIRING POSITION. A replenisher or gravity tank is provided in connection with the recoil cylinder which assures the recoil cylinders being full at all times and also takes care of any expansion of the oil due to heating. Its capacity is about 17 quarts. The recuperator mechanism consists of two connected cylinders, one containing the piston and piston rod which are attached to the breech lug, while the other contains a mushroom valve and a dia- phragm. The diaphragm separates the oil, contained in the first cylinder and part of the second cylinder, from the high-pressure air, which compels the return of the gun into battery after recoil. Nor- mally a small amount of oil must be between the valve and diaphragm. Oleonapthe is the liquid used in this recoil mechanism. The amount of oil in the recoil and recuperator "mechanism is shown by indicators, so that it can always be seen whether or not they need filling. 258 259 The top carri(( are forced up through the handle and out of the gun. When the gas ejector is drawn out, cold air is sucked through the handle and METHOD OF LOADING TRENCH MORTAR. into the gun. The head is threaded to receive a wire brush or a sponge head whenever it is desirable to clean or sponge out the bore. The projectile is a cast-iron fragmentation shell with vanes, weigh- ing approximately 53 pounds loaded, and containing a bursting charge of approximately 11 pounds of high explosive. The projec- tiles are fitted with delay and nondelay fuzes. The propelling charge consists of sporting ballistite contained in silk bags of 1 and 2 ounces capacity. With these two sizes of bags a number of combinations can be obtained and the range varied accordingly. The maximum charge is 9 ounces and the minimum 3 413 ounces. The bags are held in place between the vanes of the shell by a propelling charge bag holder. The charge is ignited by an ignition cartridge made from a standard rifle cartridge which is fired by impact with the firing pin when the shell reaches the bottom of the barrel. REAR VIEW OF MORTAR. Weights, ballistics, <-1<: Over-all length of barrel inches 57 Weight of barrel pounds 162 Weight of base do 75 Weight of platform do 160 Weight of sub-base , do 530 \Veightofshell, loaded (approximately) do 53 Weight of shell box do 10 Range, minimum meters 200 Range, maximum do 1, 700 PROSPECTUS. All wars have stimulated the development of implements of war- fare. During the recent World War new implements of war have been conceived and developed, while others have been given the supreme test and found capable of further development. Of the problems arising from the war none is more important or more in- teresting than the development of artillery materiel. In analyzing it, a brief consideration of its state before the war and the effect of the World War upon it, both in this country and abroad, is necessary. The field gun with which our Army was equipped prior to 1917 was developed about 1902 to meet the demands for a stable gun car- riage one in which the aiming of the piece was not disturbed by the shock of firing. From then on, no marked developments in design took place until the invention of the split-trail carriage, by which large increase in both traverse and elevation of the piece was made possible. In 1912 the design of such a carriage was initiated, which, after exhaustive tests, was put into production late in 1916. The design of howitzers and medium-caliber guns was limited by road conditions in this country. In these pieces power was sacrificed to obtain the necessary mobility. It had generally been considered impracticable to use heavy siege guns and howitzers in the field on this continent; therefore, none had been provided for our mobile troops. Practically all French and British designs for practically all cali- bers of guns and howitzers were adopted for war manufacture. The French 75-millimeter field gun was put into production because the American split-trail carriage had not been thoroughly tried out in service, and the British 75 was ordered because production facilities were available. The United States entered the war with neither an adequate engi- neering force to develop new designs nor a trained production force to organize manufacture. It had merely a handful of materiel and practically no facilities to produce more. Our allies not only furnished us materiel, but gave us their designs and production engineers to assist us in organizing production. Most of our engineering talent was required to solve the problems of production. Although work- ing under war pressure, time was too short to secure results. Had the war continued, some real development work might have been accomplished with the large, earnest organization built up during the war. (414) 415 Considerable development of new types of materiel was carried out both here and abroad, but as far as pertains to mobile artillery the war mainly was fought with pre-war types of field pieces. The out- standing accomplishment was the introduction by the French of the " G. P. F." and their antiaircraft artillery. The British gradually improved the range characteristics of their artillery and had under way an excellent design of a new field gun. The Germans easily ranked first in the development of artillery during the war. They developed and manufactured greatly im- proved pieces of all calibers. They recognized the value of range, not only in the design of more powerful guns of a given caliber, but also in mounting these guns on carriages so that their maximum range could be secured. By the use of these pieces the Germans caused much concern to the allied artillery commanders. Prior to the war, progress in the mechanical arts caused by the development of the gas engine had had no appreciable effect upon the design of artillery materiel. The field piece had been conceived in terms of the horse, the mountain howitzer in terms of the pack mule, therefore very little progress had been deemed possible as the horse was a fixed quantity. The perfection of the gas engine, how- ever, removed the horse as a limiting factor. The development of the automobile industry permitted high speeds of vehicle propul- sion, and created a demand for alloy steels of high physical prop- erties. All these factors became important to artillerymen, for it is evident that mechanical traction permits the increased weights required for long-range artillery; increased speed permits rapid strategic concentration of artillery; high-grade steels permit greater power in guns. Since the armistice the sentiment of our artillerymen is unani- mously in favor of pieces of greater range, greater elevation, and greater mobility. This sentiment found expression in the reports of the various service boards and especially in that of the Wester- velt board. The report of this board was approved by the Chief of Staff, and its recommendations have become the fundamental specifications for mobile artillery materiel. Ever since, the efforts of the ordnance engineer have been devoted mostly to the develop- ment of design under the Westervelt board program. Under that program the same calibers of pieces as used during the war will be developed, but they will have greater range, greater flexibility of mount, and greater mobility. Longer range will be attained partly through ammunition de- velopment, and partly by increase in the length and muzzle velocity and elevation of the gun. As mobility requires lightness, the weight of the gun will be reduced as much as possible. To secure this, three 5516O 21 27 416 lines of development are being followed : First, by using material of higher physical qualities; second, by wire- wrapping the tube; and third, by the " auto-frettage " process. At present, no new problems are involved in the construction of the wire-wrapped gun. By the use of wire, lower-grade metal can be utilized in the forgings. Guns made by this process are slightly heavier than those made of chrome alloy steel. In the auto-frettage method of construction, the gun is built up of a few pieces of steel of medium physical qualities. The walls of the gun are internally stressed beyond their elastic limit by internal hydraulic pressure. The condition set up is similar to that pro- duced by the shrinking process. The process is also a cheaper one than either the built-up or the wire- wrapped method of construction. Much research work still remains to be done in determining the proper form of rifling, the effect of variation of elements of the bore upon the life of the gun, the production and heat-treating of metals used in gun construction, and in checking the fundamental formulae of gun design. The trend of design for field artillery now proposed and under way shows several digressions from the present practice : Motor transportation promises to almost completely revolutionize artillery design. A motor-drawn carriage is not so limited in weight as the horse-drawn type, thus permitting heavier and more powerful weapons. At the same time the carriage must be designed to with- stand the more severe usage of motor traction. For pack howitzers, and field and siege pieces of 75-millimeter and greater caliber, the hydropneumatic recuperator is being employed. The St. Chamond-type recuperator is used for 75 and 105-millimeter calibers and the Filloux-type for 4.7-inch to 8-inch calibers. New developments have not been made in these types since the armistice. They have been merely adapted to meet the new conditions imposed. During the war great difficulty was experienced in the production of recuperators. Because of the use of oil and air under high initial pressure extremely fine workmanship was required in the finishing of the bore of cylinders and in the manufacturing of pistons. De- velopment along these lines is being carried on in which the air is con- fined in a metal bellows, thereby eliminating the complex pistons now necessary. Such a system also offers much simpler production prob- lems in the degree of finish required in the bores of the recuperators. Two independent lines of carriage development are being pursued the wheel type and the caterpillar type. Common, desirable charac- teristics are high elevation, wide traverse, a minimum depth of pit for clearance of recoil parts at high elevation, and stability at all elevations. The condition of high elevation and minimum depth of pit has necessitated placing the center of trunnions of the tipping 417 parts in the rear of their center of gravity, and equalizing the forces required to elevate and depress by an equilibrating system. Although the equilibrating system adds weight and complexity to the gun car- riage, the advantages thus derived more than offset the former. Bringing the center of rotation of the gun to the rear and the use of variable recoil permits lowering the axis of the gun, which is ad- vantageous in permitting lightness of construction and shortening of the trail. Wide traverse has resulted from the use of the split trail at the ex- pense of weight and simplicity of construction. The split trail 75- millimeter carriage weighs about 700 pounds more than the box trail carriage. This is due partly to the greater elevation 80, compared with 45. Provisions for elevating the pieces beyond that required for maximum range is causing complication of design and increased weights. The bottom carriage must be built out farther from the axle to permit clearance at the higher elevations, and this is expensive in weight. The Westervelt board report contemplates a gun and a howitzer mounted on the same carriage. This simplifies production and sup- ply, but complicates the design of the carriage. It is difficult to secure the same reactions in the carriage from both gun and howitzer. For example, the 4.7-inch gun materiel is heavier than it need be because the 155-millimeter howitzer demands a heavier carriage. The ideal of the artilleryman is the reduction of the number of calibers to a minimum and the standardization of mounts. The de- sirability of such a program is apparent to the department charged with production and maintenance. However, the mission of the piece, not the desirability of standardization, must fix its characteristics. Marked development is being attempted in sighting systems. The field-gun sight follows in principle that developed for the 75-milli- meter model of 1916 materiel, but is much more compact, and the sight for heavier guns will be a modified quadrant sight like that used on the 155-millimeter howitzer but with a panoramic sight. For accom- panying fire-control instruments various improvements are now in progress. In the war models of motor-carriage mounts little attention could be given to reduction in weight and to refinement in design. The possibilities of development of these types of gun mounts should not therefore be judged by the materiel built under war contracts, nor even by that now being constructed. Especially such essential char- acteristics as accessibility of parts for maintenance and elimination of mechanical weakness in details of construction must be worked out by experience. In considering any model the possibilities of perfecting the design into a desirable machine must be given the greatest weight. 418 Motor-carriage development is now proceeding along two lines: first, the track-laying type found in tractors; and second, a combina- tion wheel and track-laying type in which the mount may be operated on wheels on good roads or on tracks where road conditions are bad. Both types are self-propelled and have similar gun character- istics; weights are about the same; speeds are similar off roads; while the second type promises greater speeds over good roads. Because of the promise of both types, light and heavy gun-pilot ma- teriels of both are being built. 75-millimeter gun and 105-milli- meter howitzer carriages have been designed and built by the Holt Caterpillar Company and by the Front Drive Motor Company. Good comparative tests of the two principles of construction should be obtained from these pilots. The ideal traverse as expressed by the Westervelt board report is 360. This is being secured only in antiaircraft mounts in which the gun is pivoted on a pedestal. Mounting guns on a pivot like that in the antiaircraft mount requires increased height of trun- nions and heavy mounts. In the infantry accompanying howitzer an attempt is being made to develop a piece which can be used either as a direct-fire gun against tanks or as a howitzer, taking the place of the 3 -inch trench mortar. Guns of both 1.8-inch and 2.24-inch caliber are under test. They will be capable of being broken up into man loads. Two calibers of antiaircraft guns are being developed 3-inch and 4.7-inch. The sighting system permits the application of azimuth and elevation corrections and superelevation without disturbing the pointing of the sight. Compressed air will be used for loading. In the heavier gun, a muzzle brake will be developed in order to lessen the load on the recuperator. With other guns, almost 85 per cent of the recoil energy has been absorbed in a muzzle brake, but only about half that efficiency is expected in this case. For antiaircraft work, another big problem is to develop a satisfactory sighting and fire- control system. The latest development in sighting systems for antiaircraft artil- lery involves the removal of all sighting instruments from the car- riage and the furnishing of graduated scales only for elevation and traverse, thus eliminating the greatest cause of complexity in the gun mounts. The piece will be laid entirely by indirect fire methods from data furnished from a central station. In general, it will be seen from the above that future artillery will more nearly approach the ideal, to the degree that the prin- ciples of high power and swift transportation are incorporated in the design. In war the former is probably the first demanded, although in time of peace it is sometimes overshadowed by the latter. ADDITIONAL COPIES OF THIS PUBLICATION MAT BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. 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