GIFT OF 183228 2( Ordnance Department Document No. 2033 HANDBOOK OF ARTILLERY INCLUDING MOBILE, ANTI-AIRCRAFT AND TRENCH MATERIEL PREPARED IN THE OFFICE OF THE CHIEF OF ORDNANCE May, 1920 WASHINGTON GOVERNMENT PRINTING OFFICE 1920 ORDNANCE DEPARTMENT Document No. 2033 ffice of the Chief of Ordnance WAR DEPARTMENT, WASHINGTON, May, 1920. The following publication, entitled " Textbook of Artillery, Includ- ing Mobile, Anti-Aircraft, and Trench Materiel, - 1 ' 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, Washington, D. C. BY ORDER OF THE SECRETARY OF WAR. PEYTON C. MARCH, General, Chief of Staff. OFFICIAL : P. C. HARRIS, The Adjutant General. (3) 432322 PREFACE. The data in this book is 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. On this basis, the descriptions and drawings have been made simple and technicalities have been reduced to a minimum, bringing out the differences and similarities of the various types of artillery materiel. . This publication has been prepared in the mobile gun carriage sec- tion of the Artillery Division. The general discussion on the design and characteristics of mobile artillery is intended for the instruc- tion of student officers and enlisted specialists schools. The first edition of this book is to be distributed to various educa- tional institutions for a trial use in their classes and the results of this trial should be productive of many constructive criticisms so that the second 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. Communications should be addressed to the Chief of Artil- lery Division, Office of the Chief of Ordnance, Washington, D. C. Murray H. Resni Coff. LIST OF CONTENTS. Page. List of illustrations .' 7 Table of equivalents 14 Brief history of guns and artillery materiel '. 15 Artillery, classes of 21 Mobile artillery, types of 21 Guns, their functions and construction, including breech mechanisms 24 Mounts for mobile artillery 28 Recoil brakes and methods of counterrecoil 31 Aiming devices and sighting methods. 39 Accompanying vehicles 45 37-millimeter gun materiel, model of 1916 50 37-millimeter (1 pounder) gun carriage (Bethlehem) 56 2.95-inch Vickers-Maxim mountain gun materiel (with pack outfit) 59 75-millimeter gun materiel: Model of 1916 materiel 65 Model of 1916 MI materiel 78 Model of 1897 MI (French) materiel 80 Model of 1917 (British) materiel 94 Gun carriage limber, model of 1917 (British) 106 Gun carriage limber, model of 1918 110 Gun caisson, model of 1918 113 Gun caisson limber, model of 1918 116 3-inch gun materiel 118 Guns, models of 1902, 1904, and 1905, and carriage, model 1902 120 Gun limber, model of 1902 ]30 Gun caisson, model of 1902 132 Gun caisson, model of 1916 134 Gun limber, model of 1916 .- 137 Battery wagon, model of 1902 138 Battery wagon, model of 1902 MI 139 Store wagon, model of 1902 140 Store wagon, model of 1902 MI 141 Forge limber, model of 1902 .143 Store limber, model of 1902 146 Forge limber, model of 1902 MI 145 Store limber, model of 1902 MI 146 Battery and store wagon, model of 1917 147 Battery reel, model of 1907 150 Reel, model of 1909 MI 152 Cart, model of 1918 155 Wheels: 56-inch (steel tired) 158 57-inch by 3.5 inch (rubber tired) 158 Reel, model of 1917, for caissons 159 Automatic pole support 160 (5) :/ 6 Page. 4.7-inch gun m*.t6jiel 131 Gun and carriage, model of 1906 166 Gun carriage limber, model of 1905 175 Gun caisson, model of 1908 178 Gun limber, model of 1908 180 Gun caisson, model of 1916 182 Gun caisson, model of 1917 186 5-inch, 60-pounder gun materiel (British) 189 Gun, Mark I, and carriage, Mark II 193 Gun carriage limber, Mark II 196 Ammunition wagon, Mark II 199 Ammunition wagon limber, Mark II 203 155 howitzer materiel, model of 1917 (Schneider) 207 155 howitzer materiel, model of 1918 (Schneider) 211 Howitzer and carriage, model of 1918 216 Howitzer carriage limber, model of 1918 223 Howitzer caisson, model of 1918 225 155 gun materiel (Filloux) 229 Gun and carriage, model of 1918 234 Gun carriage limber, model of 1918 242 6-inch gun materiel, model of 1917 (British) 245 7-inch naval tractor mount, Mark V 249 8-inch howitzer materiel (Vickers) 259 Howitzers, Mark VI and VIII^, and carriages, Marks VI and VII 268 Howitzer carriage limber, model of 1917 (Vickers) 278 Firing platform and wagon, model of 1917 (Vickers) 281 9. 2-inch howitzer materiel (Vickers). 283 Howitzer and carriages, Marks I and II =. 288 Howitzer transport wagon 296 Howitzer carriage transport wagon 298 Howitzer platform transport wagon 299 240-millimeter howitzer materiel (Schneider) 300 Howitzer and carriage, model of 1918 307 Accessories 312 Transport wagons and limbers 318 Antiaircraft artillery 322 3-inch antiaircraft gun materiel, model of 1918 326 3-inch antiaircraft gun mount, model of 1917 340 75-millimeter antiaircraft truck mount, model of 1917 354 Trench warfare materiel 365 3-inch Stokes' trench mortar, Mark 1 369 6-inch Stokes' trench mortar, Mark 1 373 Prospectus 378 LIST OF ILLUSTRATIONS. Pago. Frontispiece. Sixteenth-century artillery 16 French artillery, 1800-1850 18 Recoil brakes and methods of counterrecoil : Hydraulic brake (throttling bar) 32 Hydraulic brake (valve) 32 Hydraulic brake (central throttling) 33 Counterrecoil mechanism (spring, concentric columns) 34 Oounterrecoil mechanism (spring, telescopic). . 34 Hydro-spring recoil system 34 Hydro-pneumatic recoil system with floating piston 35 Hydro-pneumatic recoil system with fluid in direct compact with the air. . 35 Counterrecoil mechanism (hydro-pneumatic, central buffing) 36 Aiming devices: Elevating systems 40 Panoramic sight 41 Gunner's quadrant 42 Accompanying vehicles : Tractors hauling artillery 46 75 mm. gun carriage, mounted on trailer ^47 37-millimeter gun materiel, model of 1916: Rear view of carriage in battery position : 49 Carriage and ammunition cart, limbered 50 Left side view of tripod mount in battery position 51 Tripod mount in firing position 53 Gun disassembled on the march (wheels and axles left in the rear) 54 Gun and personnel on the march (ammunition cart left in the rear) 55 37-millimeter (1-pounder) gun carriage (Bethlehem): Side view of carriage 57 Rear view of carriage 58 2.95-inch Vickers-Maxim mountain -gun materiel (with pack outfit): Carriage in firing position 60 Pack outfit on mule back 61 Rear view of carriage in battery - .62 Detailed view of gun 63 Side view of carriage in battery 64 75-miUimeter gun materiel, model of 1916: Right side elevation of carriage 66 Front view of carriage 66 Plan view of carriage 67 Rear view of carriage 68 Left side view of carriage 69 Breech mechanism 72 Longitudinal section of recoil and counterrecoil mechanism 73 Gun at maximum elevation 74 Elevating mechanism 75 Carriage and limber in traveling position 76 Traversing mechanism 77 (7) 8 75-millimeter materiel, model of 1897 Ml (French) : Page. Left rear view of carriage 81 Front view of carriage 82 Longitudinal section of gun and carriage 84 Breech mechanism 85 Right side elevation of carriage 87 Traversing and brake operating mechanism 88 Left side view of carriage 89 Abatage positions of carriage 90 Plan view of carriage 91 Sight, model of 1901 92 75-millimeter gun materiel, model of 1917 (British): Front view of carriage 94 Left side elevation of carriage 95 Rear and front elevations of carriage 96 Rear view of carriage 97 Breech mechanism 99 Recoil-controlling system 101 Elevating and range gear 103 Traversing gear 104 75-millimeter gun carriage limber, model of 1917 (British): Front view of limber 106 Right side elevation of limber 107 Rear and front elevations 108 Rear view of limber 109 75-millimeter gun carriage limber, model of 1918: Rear view of limber. 1] 1 Front view of limber Ill Assembled views of limber 112 75-millimeter gun caisson, model of 1918: Front view of caisson 113 Assembled views of gun caisson 114 Gun caisson and gun caisson limber, limbered 115 75-millimeter gun caisson limber, model of 1918: Front view of caisson limber. . 116 Assembled views of gun caisson limber 117 3-inch gun materiel, model of 1902: Front view of carriage 119 Rear view of carriage 119 Left side elevation of carriage 121 Gun, models 1902, 1904, and 1905, 122 Breech mechanism 123 Recoil -controlling mechanism 125 Carriage and limber, hauled by tractor 126 Carriage and limber in traveling position . . . .^ 126 Range quadrant 127 Rear sight 128 3-inch gun limber, model of 1902: Rear view of limber 130 3-inch gun caisson, model of 1902: Front view of caisson 132 3-inch gun caisson, model of 1916: Front view, showing door swung upward exposing ammunition 134 Front and side elevations of caisson. . 135 9 3-inch gun caisson limber, model of 1916: Page. Side and rear elevations of caisson limber 136 Battery wagon, model of 1902 Ml: Rear view of battery wagon > 138 Store wagon, model of 1902: Side view of store wagon 140 Side view showing store wagon and limber, limbered 142 Forge limber, model of 1902 Ml: *Top view showing interior of forge limber 143 Assembled views of forge limber 144 Store limber, model of 1902 Ml: Top view showing interior of store limber 146 Battery and store wagon, model of 1917: Rear right side view of battery and store wagon 147 Assembled views of battery and store wagon 148 Battery reel, model of 1917: Left side view of battery reel . 150 Reel, model of 1909 Ml: Rear view of reel 152 Assembled views of reel 153 Front view of reel 154 Cart, model of 1918: View showing reel and cart, limbered 155 Rear view of cart 155 Assembled views of cart , 156 56-inch wheel : Side view of wheel 158 Reel, model of 1917, for caissons: View showing reel mounted on caisson 159 Front and side elevations of reel 160 Automatic pole support: Sectional diagram of pole support 160 4. 7-inch gun materiel, model of 1916: View showing carriage and limber in traveling position 161 Left side view of carriage in battery 162 Assembled views of carriage equipped with band brakes 163 Left front view of carriage equipped with band brakes : 164 Assembled views of carriage equipped with tire brakes 165 Front view of carriage equipped with tire brakes 166 Breech mechanism 166 Firing mechanism 167 Longitudinal section of gun and carriage 168 Front view of carriage equipped with band brakes 169 Rear right view of carriage 170 Elevating and traversing mechanisms 170 Range quadrant 171 Rear view of carriage equipped with band brakes 172 Rear sight 173 Front view of carriage equipped with tire brakes 174 4.7-inch gun carriage limber, model of 1905: Front view of limber 175 Assembled views of limber 176 4.7-inch gun caisson, model of 1908: Right side view of caisson 178 10 4. 7 -inch gun limber, model of 1908: Page. View showing gun caisson and limber, limbered 180 4.7-inch gun caisson, model of 3916: Right front view showing chest doors open exposing diaphragms 182 Assembled views of gun caisson 183 Front view of gun caisson 184 4.7-inch gun caisson, model of 1917: Assembled views of gun caisson 187 5-inch (60-pounder) gun materiel (British):' Rear left view of carriage in battery 189 Carriage and limber in traveling position 190 View showing trail connected to limber 191 Rear right view of carriage 194 5-inch (60-pounder) gun carriage limber, Mark II (British): Front view of carriage limber . . 196 Rear view of carriage limber 197 5-inch (60-pounder) ammunition wagon, Mark II (British): Front view of ammunition wagon 199 Rear view of ammunition wagon 200 Ammunition wagon and ammunition wagon limber, limbered 202 5-inch (60-pounder) ammunition wagon limber, Mark II (British): Front view of ammunition wagon limber 203 Rear view of ammunition wagon limber 204 155-millimeter howitzer materiel, model of 1917 (Schneider): Right side view of carriage in traveling position 207 Carriage in battery position (rear view) 208 Front view of carriage in battery position 209 Side view of carraige en route 209 155-millimeter howitzer materiel, model of 1918 (Schneider): Traveling position of carriage and limber 210 Assembled views of traveling position 212 Detail view of howitzer . . . . 214 Breech mechanism 215 Firing mechanism 217 Recoil and counterrecoil mechanism 218 Longitudinal section of howitzer and carriage 220 Quadrant sight 221 155-millimeter howitzer carriage limber, model of 1918 (Schneider): Plan and right side elevations 224 155-millimeter caisson, model of 1918 (Schneider): Rear view of caisson 225 General assembled views 226 Front view of caisson 228 155-millimeter gun materiel, model of 1918 (Filloux): Traveling position (right side) 229 Left-side view of carriage and limber in traveling position 230 Rear view of carriage in battery position 231 Carriage in traveling position (rear view) . ; 231 Longitudinal section of gun and carriage 232 Maximum elevation of gun 234 Breech mechanism 235 Breech mechanism and counterbalance cylinder 236 Carriage in firing position 237 Rear view of carriage in traveling position 238 Accessories and caterpillar wheel shoes 239 Elevating and traversing mechanism 240 11 155-miilimeter gun carriage limber, model of 1918 (Filloux): Page. Front view of limber 242 Front view of limber, showing caterpillar wheel shoes, mounted on wheels . . 243 Detailed view of limber 244 6-inch gun materiel, model of 1917 (British): Plan view of carriage 246 Left-side elevation of carriage .' 247 7-inch naval tractor mount, Mark V: Carriage and limber in traveling position (front view) 249 Rear view of carriage 250 Left-side view of carriage in battery 251 Carriage and limber in traveling position (rear view) 253 Top carriage and axle details 254 Assembled view of hydraulic brake 255 View of axle mounted in track layer 256 Side elevation of track layer ." 257 Carriage in battery position, showing maximum elevation of gun 258 8-inch howitzer materiel (Vickers): Carriage in battery position (Mark VI) 259 Carriage and limber in traveling position (rear view) 260 Carriage in battery position (Mark VII) 262 Rear view of carriage, showing maximum elevation of howitzer 263 Right-side view of carriage in battery 264 Left-side elevation of Mark VI carriage 267 Rear right-side of carriage in firing position 268 Detailed view of howitzer (Mark VI) 269 Breech mechanism of Mark VI howitzer 270 Breechblock 271 Firing mechanism 272 Front view of howitzer carriage 273 Elevating and traversing mechanism 274 Howitzer carriage mounted on firing platform ; 275 Sight assembled 276 8-inch howitzer carriage limber, firing platform and wagon, model of 1917 (Vickers): Limber in traveling position (front view) 279 Materiel en train and in battery 280 9.2-inch howitzer materiel (Vickers): Left-side elevation of carriages assembled 284 Front view showing maximum elevation of howitzer 285 Loading position, showing shell on tray ^ 286 Longitudinal section of carriage 287 Rear view of carriage, showing howitzer at maximum elevation 288 Breech mechanism (Mark I) 289 Breech mechanism (Mark II) 290 Gear regulating recoil 291 MetKod of loading, showing loading gear mechanism in action 292 Right-side view of carriage in battery 292 Traversing gear 1 293 Sight assembled 294 9.2-inch howitzer transport wagon (Vickers): Method of mounting howitzer 296 Materiel en train. . 297 12 240-millimeter materiel, model of 1918 (Schneider): p age . Front view of carriage, showing maximum elevation of howitzer 300 Materiel e"n train 301 Carriage in loading position 302 Method of loading the howitzer with rammer car 304 Left elevation of carriage with howitzer at maximum elevation 305 Breech mechanism 306 Mounting the cradle 308 Recoil and recuperator mechanism 309 Elevating and quick-loading gear mechanism 310 Mounting the top carriage 311 Method of lowering platform 312 Sight assembled 313 Erecting frame in position 314 Left-side view of carriage 316 Mounting the howitzer 317 240-millimeter howitzer transport limbers and wagons: Howitzer transport wagon 318 Cradle transport wagon 318 Top carriage transport wagon 319 Platform transport wagon 319 Antiaircraft artillery: Antiaircraft artillery in action 323 3-inch antiaircraft gun materiel, model of 1918: Carriage in traveling position 325 Carriage in battery position (front view) 327 View showing outriggers folded 328 Longitudinal section of carriage 329 Breech mechanism 330 View showing right rear outrigger with jack spade and float removed 332 Side view of carriage in battery position 333 Assembled view showing carriage in firing position 335 Front view of trailer 336 Sight on left side of carriage 337 Sight on right side of carriage 338 3-inch antiaircraft gun mount, model of 1917: View showing mount in action 340 Longitudinal section of gun mount 341 Right side elevation of gun mount 342 View showing right side of mount 343 Breech mechanism 345 Vertical .section showing breech open 346 Elevating and traversing mechanisms 349 Left side elevation of gun mount 350 7 5 -millimeter antiaircraft truck mount, model of \917: Truck in traveling position (right side view) 354 Plan view of truck mount 355 Sectional elevation of gun mount 356 View showing truck mount in action 357 Gun mount showing gun at maximum elevation 360 Truck in traveling position (left side view) 361 Firing and stability jacks 363 Truck mount in battery position 364 13 Trench warfare materiel: Page Trench warfare 366 Arrangement of trenches 367 3-inch Stokes's trench mortar, Mark I: Mortar in action 369 Front view of trench mortar 370 Rear view of trench mortar 371 fi-inch trench mortar, Mark I : Diagrams showing preparation of trench mortar for action 374 Left side view of mortar 375 Method of loading trench mortar 376 Rear view of mortar 377 Self-propelled caterpillar Mark II: Plan view 379 Traveling position, front view 380 Traveling position, rear view 381 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) A BRIEF HISTORY OF GUNS AND ARTILLERY MATERIEL. In taking up the study of guns, the student should know something of their history, the development of guns and gun carriages, and the reason for the various changes in ordnance materiel which have taken place from time to time. The first use of guns or cannon as a medium for hurling projectiles by means of gunpowder is buried in obscurity; we have knowledge of Chinese using a form of gunpowder, not, however, for military purposes, but for pyrotechnics, at a period long before the Caucasians. 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 readiest means at first was the throwing of stones or spears with the hand; but the effect of the missile proved so often 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 inven- tion 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 at 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 more essentially the universal weapon, the cross-bow being a comparatively modern invention, and its use confined almost entirely to Europe. The cross-bow was greatly used for sporting as well as military purposes ; and it must have been a cross-bow that William Tell employed in his notable feat. The Genoese and Gascons were the most famous cross-bow men in the armies of Europe. The cross-bow 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 evidently intended as guides for elevation. The invention of gunpowder is possible to trace back 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 18322820 2 (15) 16 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 like expressions. The ancient Indians made great use of explosives, including gun- powder, 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 Constantinople. Both may be correct, but certain it is that it, 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 defended in 1247 by can- non throwing stones ; Mibela in Spain was also defended by a machine resembling can- non, when besieged in 1259; in 1273, Abou Yousof made use of cannon throwing stone balls at the siege of Sidgilmessa; and in 1308, Ferdinand IV of Castile, at the siege of Gibraltar, employed guns (or Marquinas de Truenas); and in 1311, Ismail attacked Bazas, a town of Granada, with machines throwing balls of fire with a noise resembling thunder. These seem to 4 confirm the opinion that the use of cannon and powder was known to the Arabs or Moors and introduced by them into Spain, from whence it spread over Europe. In the chronicle of the town of Ghent for 1313 it is stated that the town was possessed of a small cannon; and in the records of the Florentine Republic mention is made in the year 1325 of two officers being ordered to manufacture cannon and iron bullets for the defense of the castles and villages belonging to the Republic. The first German cannon belonged to the town of Amberg, and bears the date of 1301. The English appear to have imported them from Flanders, for King Edward III in 1327 employed some Hainaulters who used them in his war with the Scotch. In 1331 cannon were used by the King of Granada against Alicante, in 1339 at the siege of ARTILLERY OF THE SIXTEENTH CENTURY. 17 Puy-Guillem, and in the same year at the siege of Cambray by Edward III, in 1340 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 fourteenth 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 accounts of the town of Nuremberg as having been spent in purchasing cannon and guns; and in 1365 Duke Albert of Brandenberg defended Einbeck very effectually "with fire boxes." The first records show that the Huns used artillery at the siege of Cividale, Italy, in 1331. The materiel 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 con- structed of wood, wrapped with wire or iron bands, and the pro- jectiles 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 the guns out into the field of 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 ord- nance department of Edward III consisted of 340 men, with but 12 artillerymen, showing that at that time not much attention was paid to what is now an indispensable arm of the service. In 1415 the numbers had increased to 25 " master-gunners " and 50 "servitour- gunners." The gunner was the gun captain and had general charge of the gun and stores. In action he laid the piece and did the actual firing. The early cannon of Europe were known by various names in the different countries. 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 Netherlanders "voghdeer" or " veugliares." Besides these terms there were many others applied to the various models, but it was not until the commencement of the fifteenth century that cannon were classified and named according to their size. Cannon was not adopted or manufactured in France until 1338, and even for many years afterwards the French looked upon those nations who used them as barbarians. The early cannon were made of wrought not cast metal, the first account we have 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 18 19 is said to have boon 48 inches in diameter and the stone bullet to have weighed 600 pounds. The greatest example of artillery in the fifteenth century was at the siege of Constantinople in 1453, by the Turks. They used a type of mortar that hurled huge stones, some weighing 700 pounds. Some of these guns survived to engage the British in 1807; the majority of artillery at that date was for siege work. Barons who had quarrels with their neighbors would rent ordnance and go out and batter down their castles. 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, 1419 to 1424, it was not until the Thirty- Years War that they really displayed a mobile nature. The French had invented the limber, and the con- nection 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 gunner sitting directly behind 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 transportation of the heavier guns. 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 cannoneer on each of the lead horses. The ammunition carried was 100 rounds of solid shot. The howitzer, needed for its high angle of 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 shrapnel came into use. It was known as case shot and the type 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. 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 conflict. Direct laying was the only method of fire employed at this time. With the breechblock came the quick-firing gun. This called for a recoil mechanism, in order that the lay of the piece would not be seriously disturbed as a result of 20 firing. The vast amount of smoke produced with the powder then in use hid the target from the gunner and, unless quite a wind was blowing, the shooting was slow, but with the development of smokeless powder in the late nineties, this latter fault was done away with and rapid firing was possible. The first shields were put on the guns about this time also, protecting the gun personnel and making the piece more difficult to put 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 comparatively short distances, due to the impossibility of advancing artillery, ammunition, and supplies over grounds which are often muddy, full of shell holes, and otherwise difficult to maneuver 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 used for hauling field artillery, which is able to negotiate 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 caterpillar and was fired at angles of elevation varying from to 45 with very satisfactory results. This experimental caterpillar 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 caterpillar units are being built with armaments varying from 75-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 classic fications: Artillery of position and mobile artillery. Artillery of position is that which is permanently mounted in forti- fications. Mobile artillery consists of two classes: First, the artillery designed to accompany an army in the field; second, railway artillery, which requires tracks for its transportation. The first type only is dis- cussed 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 general type of gun has been decided upon, it is evident that any increase 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 purpose of the gun under consideration. We thus find it necessary to have several distinct classes of guns, ranging from the very powerful 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 this classification, based upon power, there is a second, based upon the shape of the trajectory. For the attack of targets that can be reached by it, flat trajectory fire is prefesred 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 condition 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 impor- tant to reduce this number to a minimum, both from considerations of economy and also to avoid complication in ammunition supplies. Guns were ordinarily intended for attack of targets that can be reached by direct fire; that is, by fire at angles of elevation not exceed- (21) 22 ing 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 exceed- ing 15 is necessary. There is, therefore, provided the howitzer, a short gun designed to fire at comparatively large angles of elevation. Field guns are now designed which permit fire at elevations as high or higher than is permitted by the howitzers. This is partic- ularly true of anti-aircraft 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 that of same caliber gun materiel. 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 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 23 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, 75 millimeter guns, and 155 millimeter howitzers. (6) Corps artillery, such as the 4.7-inch and 155 millimeter guns. (c) Army artillery, such as the 8-inch and 240 millimeter. Any caliber may, if required, be assigned to army artillery corps. U (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 37 millimeter. (f) Trench mortars. GUNS. THEIR FUNCTIONS AND CONSTRUCTION. U A gun is a machine by which the force of expanding gas is used for the purpose of propelling a projectile in a definite direction." The gun consists of a metal tube, closed at one end, of sufficient strength to resist the pressure of the expanding gases, in which is placed a projectile designed to move through the tube. The force of the expanding gases acting on the base of the projectile causes it to start on its flight in a definite direction. When the charge is ignited, the explosion or rapid combustion of the powder gives rise by its decomposition to a large amount of gas, which tends to expand, and to occupy a space greater than that in which the powder was originally contained; consequently, it exerts a pressure in all direc- tions, 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. (&) 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 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 rending 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 mobility 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. (24) 25 A gun is subjected to two fundamental stresses a circumferential tension tending to split the gun open longitudinally, and a longitudi- nal tension tending to pull the gun apart lengthwise. The longitudinal strength of a gun is usually greatly in excess of any requirements. It is easy to demonstrate that any homogeneous gun, i. e., a gun made of solid material and not built up, soon reaches the limit of thickness beyond which additional thickness is practically useless in giving strength to resist circumferential stress. This is due to the fact that the stress on the metal near the bore is far higher than that on the outer portion and soon reaches its maximum resistance, which addi- tional thickness of metal does not materially increase. The gun can, however, be arranged to withstand a considerably higher piessure by building it up on the principle of initial tensions. The inner lay- ers of the metal are thereby compressed so that the gas pressure has first to reverse this compression and then extend the metal. The gun barrel (or tube) supported by the contraction of the outer hoops will then be able to endure a gas pressure which can be expressed as proportional to the initial compression plus the extension, whereas in the old type of solid gun it was proportional to the extension only. In the built-up system, the outer jackets are shrunk one over the other so that the inner tube is placed in compression and the outer ones in tension. In place of one or more of the jackets, a thin wire or ribbon of steel is sometimes wound around the tube and has exactly the same effect as shrinking thin jackets one over the other. This type is known as the wire-wound gun. Guns may be composed of two, three, or more cylinders; though in practice guns are hardly ever built of more than four cylinders. All Army guns, except small howitzers or mortars, are of the built-up or wire-wrapped type. Rifling consists of a number of helical grooves cut in the surface of the bore. The soft metal of the rotating band of the projectile 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. (6) Increasing twist, or that in which the twist increases from the breech toward the muzzle end of the bore. The twist of rifling is usually expressed in number of calibers length of bore in which it makes one complete turn; this is called the twist in calibers. The twist actually required at the muzzle to maintain 26 the stability of the projectile in flight varies with the kind of pro- jectile and with the muzzle velocity. If a uniform twist is used, the driving force on the rotating band will be a maximum when the pressure in the gun is at maximum, or near the origin of rifling. The increasing twist serves to reduce the maximum driving force on the band, thus lessening the danger of stripping it with resultant loss of rotation of the projectile. This is its principal advantage over the uniform twist, though it also reduces slightly the maximum pressure in the gun. The principal disad- vantage of increasing t wist is the continued change of form neces- sary in the grooves pressed in the rotating band as the projectile passes through the bore. This results in increased friction and a higher value for the passive resistance than with a uniform twist. If the twist increases from zero at the breech, uniformly to the muz- zle, the rate of change in the tangent to the groove is constant. A twist in this form would offer less resistance than the uniform twist to the initial rotation of the projectile. But to still further diminish this resistance, a twist that is at first less rapid than the uniformly increasing twist and later more rapid has been adopted for some rifled guns. The breech mechanism comprises the breech block, the firing mechan- ism, 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 is provided with screw threads on its outer surface which engage in correspond- ing 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 a vay. 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 upan 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, described more fully and illustrated in the description of these guns. 27 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 and the length of the block may be diminished. The slotted screw breechblock is used to a great extent in oui 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 anti-aircraft 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. Howitzers differ only slightly from guns in their construction. They are shorter in length and insomuch as the chamber pressures differ materially the necessity for the long jacket is eliminated. A shorter jacket, extending only a part of the length of the tube, shrunk on in the same manner, is generally used. Interior/ ballistics treats of the motion of the projectile while still in the bore of the gun. It includes the study of the mode of combus- tion of the powder, the pressure developed, and the velocity of the projectile along the bore of the gun. By means of the formulas developed, a study of interior ballistics has made it possible to design the granulation of the powder for a given gun so as to obtain the highest possible muzzle velocity with a given weight of projectile, while keeping the pressure along the bore within the limits imposed by the strength of the walls of the gun, and the weight of the charge low enough for convenient loading. After the calculation of curves of velocity and pressure are made, the walls of the gun are calculated to withstand the expected pres- sure at each point from breech to muzzle. 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 correction in elevation and direction is required after each round. The car- riage 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 wjiole 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 and although the recoil energy is in this case greater than it would be if gun and carriage recoiled together, yet it is so gradually 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 is always less than that required to lift the wheels off the ground by rotating the carriage about the spade. The only motion of the carriage which takes place is that due to the elastic bending and rebound of its parts under the cross strain set up in discharge. These strains are inevitable since the direction of recoil 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. The principal parts of the typical gun carriage are the cradle; a device for mounting the cradle called in the different models a rocker, pintle yoke, or top carriage; the trail; the wheels and axle. The gun slides in recoil on the upper surface of the cradle and the the cradle 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 the wheels from rising off the ground on the shock of discharge. The force of the recoil of the gun, acting in the line of motion of the center of gravity of the recoiling parts, tends to turn the carriage (28) 29 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 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 the spade. 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 recoil energy. (b) Increasing the length of recoil allowed. This reduces the overturning pull. (c) Keeping the gun as low as possible, either by reducing the height of the wheels or by cranking the axle downwards. This reduces the leverage of the overturning force. (d) Increasing the length of the trail. This increases the lever- age of the steadying force. The well-designed gun carriage is one that combines these factors in a practical way, so as to give the greatest possible steadiness to the carriage, at the same time keeping within the limits of weight imposed by the necessity of mobility. Gun carriages are so constructed as to permit movement of the piece in either a vertical or horizontal plane. These motions may be simultaneous if so desired, and by a proper combination of the two motions, the axis of a gun may be aligned in any desired direc- tion within the limits of motion of its mount. The two kinds of motion are designated as follows: Rotation of the piece about a vertical axis, its inclination with the horizontal remaining unchanged, is called " traversing "; movement of the piece in a vertical plane, the horizontal projection of the axis of its bore remaining unchanged, is called "elevating." Gun carriages are provided with mechanisms for giving the pieces accurately controlled motion in both azimuth and elevation. Two types of elevating mechanisms are in common use. The first is the telescopic screw. This gives a considerable length of screw for a short assembled length and gives a rapidity of action (since the movement of the inner screw is equal to the sum of the pitches of the outer and inner screw for each turn of the pinion), combined with the nicety of adjustment of a single screw of fine pitch. In the second type 'the motion is communicated to rockers, attached to the bottom of the cradle, through the engagement of worms or pinions, with teeth cut on the circumference of the rockers. 30 This method is in use on all howitzers, and a great many guns. It allows for a very high angle of elevation, and when fitted with a quick-loading gear, allows for the rapid placing of the piece in load- ing position after firing. Movement of the gun in azimuth is accomplished in several ways; one is to pivot the cradle of the gun in a saddle which itself pivots on a horizontal transom of the trail. Another is to mount the gun and elevating gear on some form of top carriage, and pivot this top carriage over the axle. Still another is to traverse the whole piece along the axle, pivoting on the spade. This is a method used by the French in some of their designs. It has the disadvantage of only allowing for a small angle of traverse. The above principles of design are, of course, modified considerably in the case of semipermanent mounts which fire from platforms and for anti-aircraft guns which have special mountings suited to their special use. RECOIL. RECOIL BRAKES AND METHODS OF COUNTERRECOIL. The stresses to which a gun carriage is subjected are due to the action of the expanding powder gases on the piece. Gun carriages are constructed either to hold the piece without recoil or to limit the recoil to a certain convenient length. In the first case, the maxi- mum stress on the carriage is readily deduced from the maximum pressure in the gun. In the second case it becomes necessary to determine all the circumstances of recoil in order that the force acting at each instant may be known and the parts of the carriage designed to withstand this force and to absorb the recoil in the desired length. Assume the gun to be so mounted that it may recoil horizontally and without resistance. On explosion of the charge, the parts of the system acted upon by the powder gases are the gun, the pro- jectile, and the powder charge itself; the latter including at any instant both the unburned and the gaseous portion. While the pro- jectile is in the bore, if we neglect the resistance of the air, none of the energy of the powder gases is expended outside the system. The center of gravity of the system is therefore fixed, and the sum of the quantities of motion in the different parts is zero. The move- ment of the powder gases will be principally in the direction of the projectile. By formula, the weight of the gun, projectile, and charge being known, the complete relations between the velocity, time, and length of free recoil may be established. Thus far we have neglected all resistances and have considered the movement of the gun in recoil as unopposed. However, when the gun is mounted on a carriage the recoil brakes, of whatever character, begin to .act as soon as recoil begins, and consequently the velocity of recoil is less at each instant of travel than when unopposed. It is evident that the higher the resistance offered by the recoil brakes, the shorter will be the total length of recoil. A little consideration will show that if the total resistance to recoil is made constant throughout the recoil, its value will be less than the maximum value of a variable total resistance which will stop the gun in the same length of recoil. For a given length of recoil; the constant resistance will therefore produce less strain in the carriage, and for this reason is usually adopted, except where stability can be increased by using a variable pull. 18322820 3 (31) 32 FIG. A. The recoil system of a gun carriage consists of a recoil brake for controlling the recoil and limiting its length, a counter-recoil mech- anism for returning the gun to the firing position and keeping it there, and a counter-recoil brake or buffer to soften the shock as the gun runs into the firing position. Recoil brakes of the friction type were formerly used. Pneumatic brakes were also used to some extent. Both have been entirely superseded by the hydraulic recoil brake. A hydraulic recoil brake consists of a cylinder filled with liquid and a piston. Relative movement is given to the cylinder and piston by the recoil, and provision is made for the passage of the liquid from one side of the head of the piston to the other, by apertures cut into the piston or in the walls of the cylinder. The power of the brake lies in the pressure produced in the cylinder by the resistance offered by the liquid to motion through the apertures. ! f the area of the apertures is constant, it is evident that the resistance to flow will be greater as the velocity of the piston or the velocity of recoil is greater. Therefore, the pressure in the cylinder, which measures the hydraulic resistance offered, will vary with the different values of the velocity of recoil. If, however, the apertures are constructed in such a manner that the area of aperture increases when the velocity of the piston increases, and diminishes when that velocity diminishes, the variation in the area of aperture may be so regulated, that the pressure in the cylinder will be constant, or will vary in such a manner as to keep the total resistance to recoil con- stant, or it may be made to vary in any manner desired. In figure A is shown one type- of hydraulic brake. It consists of a cylinder on the inner circumference of which are formed bars of varying cross sections, called throttling bars (T), piston (p), and piston rod. Either the piston rod is secured to the carriage, the cylinder moving to the rear with the gun, or the cylinder is secured to the carriage, the piston moving to the rear inside of the cylinder. Through the piston head are cut slots or apertures through which the liquid is forced from one side of the piston to the other as the cylinder, or piston, moves in recoil. Each slot has the dimensions of the maximum section of the throttling bar with just enough clear- ance to permit operation. The area of orifice open for the flow of liquid at any position of the piston is therefore equal to the area of the slots minus the area of cross section of the throttling bars, and FIG. B. is so determined that the resistance to the flow of the liquid, or the pressure in the cylinder, is made constant or variable, as desired. In another type of hydraulic brake the throttling bars are not used, but the varying apertures are obtained by cutting grooves of varying width or depth on the interior of the cylinder. Figure B represents another method of varying the throttling grooves. The piston (P) is held rigidly from turning and the valve (V) is rotated by means of a spiral groove cut in the cylinder walls, in which the lugs of the valve slide during recoil, thus rotating the valve and varying the size of the openings through the valve and pis- ton. This method is used to a considerable extent in British design. Figure C illustrates a method of central throttling. The throttling rod (R) has a varying diameter; this causes the amount of liquid, which flows between it and the hole in the piston (P) , to vary in the manner necessary for correct throttling. This method is used in some French designs. Counterrecoil, or the return of the gun to battery after completion of the recoil, may be effected by springs or by compressed air cylin- ders; the latter, in connection with the recoil brake, forming the hydro- . | [ p^ \ ~ pneumatic recoil system. (V c= Z__ J ^~ The spring method of effecting | ~f\ counterrecoil may be used in all gun carriages on which the gun recoils in the direction of its axis. These include pedestal mounts, barbette carriages, turret mounts, and all wheeled carriages as shown in figures F arid G. In the smaller carriages of these types the springs, initially com- pressed to the desired amount, may be placed between the piston and the rear end of the hydraulic brake cylinder which is lengthened for that purpose. In some carriages of this type the hydraulic brake cylinder moves with the gun in recoil, the piston being stationary. In such construc- tions the springs are usually placed around the hydraulic brake cyl- inder, and are compressed between a flange on that cylinder in front and some fixed part of the carriage in the rear. In larger carriages the springs are arranged in separate cylin- ders with pistons of their own, two to four of these spring cylinders being required, see figures F and G. Figure D shows a spring counter-recoil mechanism (spring recu- perator) consisting of two concentric columns of springs. It is sometimes necessary to use telescopic springs as shown in figure E, when a single column would not allow sufficient recoil. These and other arrangements of counterrecoil springs will be further discussed in the description of the carriages to which they pertain. 34 oooooooooooo o >oooooooooo< o "joooooooooo [>oooooooooo< DOOOOOO o o o o {_ oooooooooooL 9 )OOOOOOOOO O<|~ - ooooooooooon FIG. D. FIG. E. Compressed gas (either air or nitrogen) is now very generally used to effect counterrecoil. Figures H, J, K, and L are diagrams of two designs of hydropneuniatic recuperators. 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 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 iRRIMGJ FIG. f=- IN-BAT- TERV OR F1RIMC3 ROSITIOM /SPRIMC3 F"IG.Gi EIMP OF" IREICOIL- - SRRIMG RECOIL- rod be fastened to the carriage. The gas is given sufficient initial compression to hold the gun in battery at all elevations. 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). AIR RIS-TOM(FP) H IN-BA-TTETR^ OR F-|RNG FLOAT-IMG PISTON FIG. K IN- BATTER V OR F"IR>MC5 F>OS|-TlOrH . L- ElfSP OF f?ETCOIL- HVORO-PINEIUMATIC REZCQJL- S^ WITH IM PIREICT OOMTAOT WITH THEI >AIR 36 The hydropneumatic recuperator (or counterrecoil mechanism) may be separated from the recoil brake or the two may be combined in one unit. 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 M B X _ JJ the counterrecoil springs or air cyl- /L c ^ "I (w L J inders, if there are such included OIL in the recoil system. FIG M The counterrecoil buffer is pro- vided for reducing the shock to the carriage as the gun is returned to the firing position by the counter- recoil 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 similar method 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 dash pot 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 37 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 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 nydraulic 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, anti-aircraft 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 counter recoil 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. 38 Under ordinary conditions the ground will resist a pressure of 40 pounds per square inch of spade surface, and knowing the pressure 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 horizontal distance of the vertical through their center of gravity from the point of sup- port 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 stability 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 affect 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 wilich it is to be fired, as well as to overcome the friction on the recoil sides as the gun runs forward to the firing position. AIMING DEVICES AND SIGHTING METHODS. Sights will be discussed briefly in this pamphlet merely to indicate their application to field, anti-aircraft, 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 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 de- termining when the axis of the gun has the predetermined direction. When the piece is sighted, both in elevation and direction by sight- ing directly 011 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, 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 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 its 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 throw- ing 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 responsibility 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 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. (39) 40 (6) The correction to this elevation required by the difference of 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 ele- vating mechanism, and the gun pointer is thus free to devote his FIG. N. , . . whole time to keeping his line of sight upon the target and is not compelled to take his eye from the telescope. The above method has the objection, however, that it is difficult to make the necessary correction in the range drum for differ- ence in level of trunnion axis. 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 field pieces 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 sight- ing becomes then of necessity, 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. 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 direction, while the range quadrant for laying in elevation 41 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 degrees or in fractions of the range (mils). 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 permits of the gun being moved and set- in elevation without any change in po- sition 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. 42) can be used in obtaining or checking the elevation. It is not the intention to go into de- tail in this handbook regarding the fire- control equipment employed for direct- ing the fire of anti-aircraft 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 anti-aircraft 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. 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. PANORAMIC SIGHT, MODEL OF 1917. 42 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- 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 : GUNNER'S QUADRANT, MODEL OF 1918. (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. (6) Engine speed of the target. (c) Altitude of the target. (d) Time of flight of the projectile to the future position of the target. The resolution of the formulas deriving the lateral and vertical deflection corrections is accomplished upon a device known as " Anti-aircraft 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 43 telescope pointers remain sighted unon the present position of the target. The great advantage of this method lies in the fact that the pre- sentation and engine sDeed can be estimated with reasonable accuracy,. 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 s^eed 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 (6) as a function 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. 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 monostatic 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. 44 (6) 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, telementry, which involves the functions, angle of site, to the future position of the target and altitude, is readily accomplished with the aid of 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 measurement of deflections and the maneuvering of its gun-laying mechanisms in order that effective fire may be conducted against a target whose movements are subject to such large displacements. ACCOMPANYING VEHICLES. In addition to the piece itself, a number of vehicles are necessary in batteries, sectors, and regimental organizations of field artillerj 7 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 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 faciliate 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 farrie'rs 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. (45) 46 47 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, but the greatest and 75-MILLIMETER GUN CARRIAGE MOUNTED ON A 3-INCH FIELD GUN TRAILER. most radical change being the motorization of artillery. Mechanical transport is at this time in such a state of development that there is no reed of dwelling upon its numerous advantages over animal draft. The origin aj x 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 guns were required. The movements of this heavy artillery in 18322820 4 48 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 motorcycles with side cars. Battalion and regi- mental headquarters are also supplied with light touring cars and Westfield military bicycles. A motorcycle is ideal for liaison and work of similar nature requiring rapid transportation for one or two individuals. The motorcycle 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. 49 The equipment is designed to make all repairs in the field, both to artillery materiel and motor vehicles. 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. 37-MILLIMETER GUN MATERIEL, MODEL OF 1916. Experience has shown that the infantry can not carry out its mission, by its own weapons, except at prohibitive less of personnel. Our automatic rifle is practically useless for ranges greater than 500 meters, and then only against personnel. The individual rifle does not offer the necessary volume of fire, while the rifle grenade, and even more so, the hand grenade, is a clcse combat weapon. Hence the taking of a machine-gun nest by a unit (con- sisting 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 cress fire. Such conditions calls for some form of artillery, effective at from 400 to 1,500 meters, against both personnel and materiel, raid 37-MILLIMETER GUN CARRIAGE AND AMMUNITION CART, LIMBERED. capable of immediate action. The field artillery is not available because of difficulty of communication and length of time neces- sary to get into action. The heavy artillery is not sufficiently mobile. Its dispersion is too great for small, definite targets, there- by 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 3 7-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 modifications of this weapon have found wide application for (50) 51 52 . its use and, due to its extreme portability, this gun is adaptable for tanks, tractors, and aircraft. 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. Weights, dimensions, and ballistics. Weight of gun and recoil mechanism (with flash hider and sight) . . . .pounds. . 104 Weight of recoil group do 34 Weight of barrel group do 38 Weight df 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 ande 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 .vidth of vehicle . . . .do. . 57 53 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. J t 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, counter recoil 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 piston is 11 inches. 54 The mount may be used either in the form of a tripod or with the axle and wheels attached. n 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. n 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, w^hich 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 stiff eners. The shield consists of three plates hinged together, and is mainly employed to protect the gunners from shrapnel and flying fragments. 55 The gun is provided with a telescopic sight for use in direct fire and a quadrant sight for indirect or masked |ire, 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 inches 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. ^ r 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. 37-MILLIMETER 1-POUNDER GUN CARRIAGE MARK A, MODEL I (BETHLEHEM). The 1-pounder semiautomatic gun and carriage was primarily in- tended for landing purposes, but it has been used in trench warfare and to accompany infantry troops. This equipment is well adapted to the latter uses, due to the fact that its weight is such, as to permit it to be readily transported from place to place by man power. The gun is made of nickel steel, with the gun body and breech end being forged in one piece. The breech mechanism is of the Bethle- hem semiautomatic type in which the breech is opened, the case ejected, and the firing pin cocked on counterrecoil. The block is closed by a spring which is compressed during counterrecoil and held in that position by the extractor until tripped by the insertion of another round. The carriage is of the long recoil type and consists essentially of a cradle, pivot yoke, trail, wheels, and axle. The cradle supports the gun, forms a housing for the recoil mechanism, and is itself supported by trunnions bearing on the pivot yoke. The recoil mechanism is located above the gun and consists of a hydraulic cylinder and counterrecoil springs. No elevating and traversing mechanisms are provided as the laying can be readily accomplished by means of a shoulder guard and grip. Open sights are furnished and a bullet proof armor plate shield affords protection for the cannonneers. Fixed ammunition is used, and is packed for transportation in steel boxes containing 60 rounds each. A hand cart for carrying four boxes, 240 rounds, is issued, the front and lid of this cart, being bullet proof. Weights, dimensions, and ballistics. Length of gun inches. . 68. 2 Length of rifling do 61. 7 Number of grooves 12 Muzzle velocity feet per second . . 2, 100 Maximum range yards. . 4, 100 Weight of charge pounds. . . 16 Weight of projectile do 1. 07 Weight of complete round do . . -. . 1.5 Weight of gun and breech mechanism do 173 Breech block Vertical sliding, semiautomatic . . Recoil (constant) inches . . 10 Weight of carriage in battery position pounds. . 800 Range of elevation degrees. . 5 to +15 Amount of traverse , do 45 Width of track inches . . 35 Line of sight Dependent. . Height of axis of bore inches . . 29 Diameter of wheels do . 42 (56) 57 58 2.95-INCH VICKERS-MAXIM MOUNTAIN GUN MATERIEL. 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 axles 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 . . .inches . . 2. 953 Length of gun do 35. 85 Weight of gun, including breech mechanism pounds . . 236 Rifling uniform, 1 turn in 25 calibers, right -hand twist. Weight of projectile do 12$ Weight of powder charge ounces . . 8 Muzzle velocity 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 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 (59) 60 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 swings 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. 61 The recoil mechanism 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 z 3 (5 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 62 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 disassembling for packing. The cradle also carries the sight bracket 63 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 on the left side of the trail. A bolt for quick release of the elevating eye pi 5 fan lock. DETAILED VIEW OF GUN. mechanism from the cradle is provided. Elevations from 10 degrees depression to 27 degrees elevation may be obtained. No traversing mechanism is provided, and transverse must there- fore be obtained by swinging the trail. e/sra//** /breech SIDE VIEW OF CARRIAGE IN BATTERY. 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 trail is fitted with a "scraper," which in reality is a short spade. It is also provided with a socket for the handspike. 18322820 5 64 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 ha\ ing 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 the steel high explosive and shrapnel shells, each weighing 12 J pounds. Each animal carries two chests containing five rounds each. 75-MILLIMETER GUN MATERIEL, MODEL 1916. The United States model 1916, 75-millimeter field gun is an adap- tation from the United States 3-inch field gun, model 1916, arranged with a split trail and having greater traverse and greater elevation than either the French or British models of this caliber. The 75-millimeter field gun constitutes the light artillery or rapid mobile field artillery of the Army. The caliber of the piece is about as large as ready horse-drawn mobility will permit. The caliber is FRONT VIEW OF CARRIAGE. equivalent to 2.95 inches, and was adopted by the French and by the Italians, while the United States had adopted the caliber of 3-inch and Great Britain a caliber of 3.3-inch, 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 types are accuracy, long range, rapidity of fire, ease of transportation, and smooth and reliable functioning. As the range depends not only on the power of the gun and on the design of the ammunition but on the elevation provided for, and (65) 66 tat 8 : II I e LJ O 2 CD cr 02 ok => LJ O O -r O lO - , 68 as the horizontal afc which could be covered by a gun with a single setting of its trail is governed by the permissible traverse, great attention was given to the mechanical features covering the vertical and horizontal limits of the gun laying, as well as to the smooth and reliable functioning of the piece. Of the above models, the French model is credited with functioning most perfectly, but the United States completed a new carriage which permits very high elevation of the gun and wide traverse. Due to the permissible elevation, the American piece outranges the French, although the French gun has a greater muzzle velocity. Roughly, the weight of the piece, including the carriage and limber, is about 4,600 pounds, which in general corresponds with the horse- drawn draft limitation over rough ground of 765 pounds per animal, REAR VIEW OF CARRIAGE calling for six horses to the piece, although four horses are frequently employed over level or hard ground. The introduction of motor tractors has altered the draft problem, but there still remains the question of facility in handling the piece by man power after battery position has been reached. As illus- trative of this it may be mentioned that the weight at the end of a 75-millimeter gun carriage trail is in the vicinity of only 100 pounds. The trails 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 the position of the trail of a 155-millimeter gun requires the use of jacks and a con- siderable 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 6f damage to the materiel when trans- ported at high speed on its own wheels must also be considered. 69 The dimensions and weight of the 75-millimeter piece permit of its being placed on a rubber-tired trailer, which allows of its being transported at high speed behind a motor vehicle. The movement of the light artillery is of utmost importance, and the 75-millimeter field gun may be considered as a gun of first rank, for it constituted the light artillery of the military powers. This weapon is accurate, has a range up to 6 or 7 miles, is suitable for the projection of high explosives, shrapnel, incendiary, smoke, asphyxiating, tear, tracer, illuminating, terrorizing, and chain projectiles, and is adaptable for barrage fire, destruction of personnel, tearing away of wire entangle- ments, destruction of fair-sized obstacles, and to some extent the destruction or protection of lines of communication. The indications are that a slightly larger caliber will supplant this caliber in order to obtain longer range and greater destructive force and either motoriza- tion or direct mounting on self-propelled caterpillars may affect the LEFT SIDE VIEW OF CARRIAGE. adoption of a new caliber, for mobility and rapidity and ease of handling are features of importance in this branch of the field artillery. Weights, dimensions, and 'ballistics. Weight of gun and breech mechanism pounds. . '< -19 Length of gun inches. . 90. 9 Caliber millimeters. . 75 Length of bore inches. . 84 Length, calibers 28 Rifling, right hand twist, zero turns from origin to point 2.89 inches from origin; from this point increases one turn in 119 calibers 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 Muzzle velocity: Shrapnel feet per second . . 1, Shell (short fuze) .do 1, 24 693 900 Shell (long fuze) do. ... 1, 876 70 Maximum range: Shrapnel (Mark IV shell) yards. . 9, 650 Shell (short fuze) '.do 12, 360 Shell (long fuze) , do. ... 11, 155 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 from ground do. ... 41. 625 Maximum angle of elevation degrees. . 53 Maximum angle of depression do 7 Maximum traverse, 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 (AMERICAN). 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 on the lower sido of the jacket. A lug on top near the for- ward end 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 under side 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. (71) 73 I SSi 74 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 sight mechanism consists principally of a rocker which is moved by two hand wheels, 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 sight scale is graduated in mils. All settings on the angle of sight scale are set oft' 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 sight mechanism? the gun and cradle only being moved upon operation of the hand- wheel. 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 battery position and by a lever from the axle seat when in traveling position. 75 76 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 shrapn.el, 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 Ml. Store limber, model of 1902 Ml. Battery and store wagon, model of 1917. Battery reel, model of 1917. * Reel, model of 1909 Ml. Cart, model of 1918. 1 The above gun carriage was originally the 3-inch gun carriage, 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 Ml with the cart, model of 1918, is issued in lieu of the battery reel, model of 1917. 77 INTERMEDIATE SHAFT GEARr ~ v-.5xLB370|)STUD. ^575* L9l2(lf)Srua. \5CROWN NUT=r\\ /T-375 CROWN C TRAVERSING STOP y .093(&J< I.B75STEEL VMS' TRAVERSING I AZIMUTH SCALE.'' . ^. . AZIMUTH POINTER.^/ ..5CROWNNUTJAPPED.625STai ^~^9bT375STb7c3UNKHEAD GERMAN SILVER SCREWS^ INSTRUCTION PLATE (TRAVERSING). ^""""" CRANK PIN;- .625 CROWN NUT.^ CRANt^LEEVC-^*^' ^-^^ -v _-- -ANGLE OF SITE BRACKET COVER(LCFT) ^TraWtRSNG HANOWHECl. SHAFT. -*" i iffTS * ...u/ vv ww.. ~>- ANGLE OF SITE BPACKET(LEFT) -^575 HANDY OILER. -HUB. ,^HANDWHEEL BODY. ^*** / .375 HANDY OILER BRONZE PLUG.' .375x I.3I20|)BOLTS. =mniZ TRAVERSING INTERMEDIATE SHAFT. -j INTERMEDIATE SHAFT BEARING. 7 _ --TRAVERSING WORM SHAFT BEARING. "^^,-is.x i.8i20g) srua '"^^-* CROWN NUT. TRAVERSING WORM SHAFT. -TRAVERSING WORM (HINDLEY.) ' X ^^ -TOP CARRIAGE. -HALF BUSH I NG^75x".T5 fTOP CARRIAGE.) \ \\\ " .125 x. 75 STEEL PIN A \ \ S> ADJUSTING NUT. WASHEP.A ^-.125 X 1.75 SPLIT PIN 75 M M.GUN CARRIAGE. MODEL OF 1916. TRAVERSING MECHANISM. 75-MILLIMETER GUN MATERIEL, MODEL OF 1916 MI. There will soon be issued to the service a number of model 1916 75-millimeter gun carriages, redesigned to mount a St. Chamoiid hydropneumatic recoil mechanism in place of the hydrospring type, and a standard 75-millimeter gun modified and fitted with a counter- weight. The new materiel will be known as the 75-millimeter gun materiel, model of 1916 ML The St. Chamond recoil mechanism as adopted for these carriages was developed during the war in 1917 by Col. Rimailho, of the French Army. This mechanism, of the hydropneumatic type, is durable and smooth in operation. The use of small cradle forgings was made possible by the introduction of high pressures in the recuperator and recoil cylinders. In order to hold these pressures, it was necessary to develop suitable packing, and the success of this recoil system is largely due to the design of these packings. The St. Chamond recoil mechanism consists of three cylinders, the middle one being the recoil cylinder, the right cylinder having an air reservoir at its forward end, and an oil reservoir at its rear end; the left cylinder, known as the recuperator cylinder, has at its forward end an air space, and at its rear end a floating piston and regulator for controlling the length of recoil. The recoiling parts are held in battery by the reaction of the air on the floating piston transmitted through the liquid against a leak- tight recoil piston. In recoil the gun moves to the rear, carrying with it the recoil piston (middle cylinder) . The energy of recoil is absorbed by the throttling of the oil through a spring-controlled orifice in the regulator valve. 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 Belleville springs. The oil pass- ing 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. The throttling during recoil is controlled by the regulator valve ? which consists of two parts, an upper stem and a lower valve stem. The lower valve stem is seated on a circular seat at the entrance channel to the valve. As the valve lifts, the throttling area becomes (78) 79 the Vertical circumferential 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 Belleville springs reacting on the stem only. To move the upper valve stem, the whole housing is lowered automatic- ally by a cam operated by the elevation of the cradle. At short recoil, the upper stem of the regulator is brought down by the cam until its lower surface is in contact with the top surface of the lower valve stem in order to control the throttling of the valve. The regulator valve is closed during the counterrecoil movement. The oil flow during counterrecoil is different from that during recoil, the counterrecoil flow path being through a small channel beginning at the inside end of the buffer chamber in the recuperator cylinder and finally emptying into the recoil cylinder. The throttling during counterrecoil takes place through a constant orifice located at the beginning of the counterrecoil channel. The tapering buffer rod on the floating piston in the recuperator causes additional throttling through the small annular area between the buffer chamber and buffer rod of the floating piston, which brings the recoiling parts to rest without shock. 18322820- 6 75-MILLIMETER GUN MATERIEL MODEL OF 1897 Ml (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, and it is understood that the American model 1916 equaled this rate; likewise, a St. Chamond gun with interrupted screw-type breech on the special St. Chamond recuperator. Apart from the personnel service to the piece, the length of time which either gun could maintain this rate of fire, or any other rapid rate of fire, is perhaps not definitely determined. 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 is likewise perhaps not definitely determined. Rapidity of firing 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 fir- ing position, and to be efficient it must be able to perform these two functions quickly, smoothly, surely, and continuously. The word " 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. The general theory of hydropneumatic recoil mechanism is not new. In its relation to light artillery its most notable exemplifica- tion in battle has appeared in the Puteaux Arsenal type of the French piece. Its virtues have been widely heralded and every effort has been made to keep its construction secret. Its several parts were (80) 81 32 83 manufactured at different points in France and these were assem- bled in a small room at the Puteaux Arsenal, and but few persons were admitted to this room. In the agreement, to manufacture of the complete recuperator in the United States, it was stipulated that the greatest secrecy should be maintained with reference to its de- sign, 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 re- duced by the long-range gun, of heavy caliber, but it is the destruc- tion 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 75-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 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 do. . 2, 657 84 85 86 75-MILLIMETER GUN AND CARRIAGE, MODEL OF 1897, Ml (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 Nordenfeld 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 reccil mechanism is of the hydropneumatic, long recoil type and contains both recoil and counterrecoil mechanisms. A gage 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 be 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, able to communicate together by means of a passage provided for that purpose. The front part of the upper cylinder (in front of the piston) is permitted to communicate freely with the air through a 87 88 if 1 Mil? 89 plug, but the forward end of the lower cylinder is closed and con- 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, a/re incorporated in the low r er 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 LEFT SIDE VIEW OF CARRIAGE. braking, in so moving, the liquid opens the valves (which are widely opened 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 90 repair depots. The recoil mechanism will function properly without the operating personnel understanding the interior mechanism. 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 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 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 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 the ground and mounting the wheels thereon, for firing. This last operation is called abatage, the three steps being indicated in the following figures: POSITION I POSITION Z POSITION 3 ABATAGE POSITION Wooden wheels, 1,334 millimeters (52.5 inches) diameter, are used, and have steel tires 3.5 inches wide. These wheels are interchange- able with the French limber wheels, but not with the American limber or caissons for the 75-millimeter gun carriages. 91 92 93 The customary shield and apron protects the gunners when under fire. The angle of site mechanism is also called the independent line of sight, because the range setting is independent of the setting of the angle of sight, which is done by the angle of sight handwheel. % The sight, model of 1901 (French), includes the collimating sight, angle of site level, and angle of site scale. It is mounted on the left side of the rocker, at the trunnions. It has no telescopic features and, therefore, its range is limited. An auxiliary angle of site level is furnished to replace the regular level and gives an additional 200 mils for use in the hilly or mountainous country. Fixed ammunition is used in this 75-millimeter field gun and is made up with 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; the powder charge; projectile; and fuze, in shrapnel; and adapter and booster in the shell. 75-MILLIMETER GUN MATERIEL, MODEL OF 1897M1 (FRENCH) A battery of 75-millimeter gun carriages, model ol 1897M1 (French) is accompanied by the following vehicles: 75-millimeter gun and carriage, model of 1897M1. 75-millimeter gun carriage limber, model of 1918. 75-millimeter gun caisson, model of 1918. 75-millimeter gun caisson limber, model of 1918. Battery and store wagon, model ol 1917. Forge limber, model of 1902M1. Store limber,. model of 1902M.1. Battery reel, model of 1917. 1 Reel, model of 1909M1. 1 Cart, model of 1918. 1 The gun and carriage are of the French design, and of both French and American manufacture. The accompanying vehicles are all of American design and manufacture. 1 For horse batteries the battery reel, model of 1917, is issued. For motorized batteries, the reel, model of 1909 Ml, with the cart, model of 1918, is issued in lieu of the battery reel, model of 1917. 75-MILLIMETER GUN MATERIEL, MODEL OF 1917 (BRITISH). The 75-millimeter gun, model of 1917 (British), was originally known as the 18-pounder, but was modified by adapting it to the 75-millimeter caliber materiel. This weapon is equipped with cus- tomary unit trail; the interference of the trail with the breech limits the gun elevation. With the split trail, the breech can pass down into the V formed by separating the two sections of the trail. The theoretical elevation for obtaining maximum range under ideal bal- listic conditions is 45 from the horizontal, and is actuallv some few FRONT VIEW OF CARRIAGE. degrees less than this. Increased range is sometimes obtained with field guns whose normal elevation is limited by setting the axles or wheels on raised surfaces, or by sinking the trail below the level of the wheels, for the purpose of pointing the gun at an elevation higher than the mechanical arrangement of the carriage permits. This is, however, a subterfuge, limited in its practical application. 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 mechanism on the 1916 model was adapted to the higher permissible elevation of the gun, and was supplied with a variable recoil, auto- matically adjusted to different elevations. The ability to outrange (94) 18322820 7 96 97 the enemy is an attainment constantly being sought, and therefore high elevation and reduction of resistance of the projectile passing through air are the means through which it was hoped to obtain the increased range desired. Likewise, a wide horizontal arc of fire, without resetting of the trail and consequent resetting of the sight- ing devices, is a great convenience and saver of time. As compared with the British model 1917, the American 3-inch model of 1902 carriage permits of a maximum angle of elevation of 15, depression of 5, and traverse of 142 mils, while the British model permits 16 elevation, 5 depression, and 142 mils traverse. The French model 1897 carriage permits a maximum angle of eleva- REAR VIEW OF CARRIAGE. tion of 19, depression 10, and traverse 106 mils. The American model 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 of - 6 -4W f a circumference). The American model 1902 carriages are arranged with an hydro-spring recoil mech- anism, and so is the British model 1917 and the American model 1916. The French model 1897 carriage is equipped with an hydro- pneumatic recoil mechanism. The basic difference of the recuperator or recoil mechanism of the French model 1897 gun, as compared with the British model and the American model, lies in the fact that the French model involved the principle of oil and compressed air for absorbing the recoil of the gun 98 and returning it to battery or firing position, and is practically self- contained in one large heat-treated steel forging, with a system of finely fitted surfaces and adjustment valves. In the British and American model recoil mechanism, oil and steel springs, instead of compressed air, are employed, with a combination of pistons and steel tubing. A reference may also be made relative to the desirability of single or unit trails as compared with the split trail. The latter allows of greater traverse, but as a new objective makes necessary a resetting of the trail, the change in setting requires much more time than with the unit trail. The split trail is heavier and the equalizing mecha- nism, necessary to the proper distribution of recoil shock to both trail sections, establishes a relative movement between the two trail sec- tions, with the result that the split trail can be set up less quickly than the unit trail on uneven ground. Weights, dimensions, and ballistics. Caliber millimeters. . 75 Weight of gun and breech mechanism pounds. . 995 Total length of gun inches. . 88. 21 Length of bore do. ... 83. 915 Rifling, right-hand twist, zero turns at origin to 1 turn in 75 inches at 9.72 inches from muzzle, thence uniform. Number of grooves 24 Muzzle velocity: Shrapnel feet per second. . 1, 693 Shell (short fuse) do. ... 1, 900 Shell (long fuse) do. ... 1, 876 Maximum range: Shrapnel (Mark IV shell) yards. . 6, 464 Shell (short fuse) do.... 8,100 Shell (long fuse) do. ... 7, 450 Weight of one round of ammunition: Shrapnel pounds. . 16 Shell do. ... 12. 3 Weight of carriage, complete f without gun) do 1. ; .*> Weight of gun and carriage, fully equipped do 2, 945 Weight of gun and carriage in battery position do 2, 860 Diameter of wheels inches . . 56 Width of track do .... 60 Length of recoil of gun on carriage do 49 Height of axis from ground do 38. 86 Maximum angle of elevation degrees . . 16 Maximum angle of depression do 5 Maximum traverse, each side of center mils . . 72 Weight of gun, carriage, and limber (British) fully equipped, also loaded with shrapnel and fuze boxes pounds . . 4, 591 Weight of gun, carriage and limber (American) fully equipped, also loaded with shrapnel and fuze boxes pounds. . 4, 458 99 100 75-MILLIMETER GUN AND CARRIAGE, MODEL OF 1917 (BRITISH.) The gun is built up of alloy steel, consisting of a tube, a series of layers of steel wire, jacket, and breech ring. The tube extends from the rear end of the chamber to the muzzle. Over the rear por- tion of the tube are wound 15 layers of steel wire. The jacket is fitted over the exterior of the tube and wire, and is secured longitu- dinally by corresponding shoulders and the breech ring, which is screwed over the jacket at the rear and secured by a set screw. The breech ring is prepared for the reception of the breech mechanism, and is provided on the upper side with a lug for the attachment of the hydraulic buffer. Longitudinal projections on each side of the jacket form guides for the gun when in the cradle of the carriage. A plane for a clinometer is prepared on the upper surface of the breech ring. Vertical and horizontal axis lines are cut on the face of the muzzle for use in verifying the adjustments of the sight. The breech block is of the interrupted screw type having two threaded and two slotted sectors. The breech recess of the gun is slotted and threaded to correspond with the threads on the block and the latter is screwed to a cylindrical section, or carrier, which is hinged to the right side of the breech. Hinged to the rear face of the carrier is a hand lever, provided with bevel teeth which engage with corre- sponding teeth on the rear face of the breech block, so arranged that when the lever is pulled to the right, the first movement of the lever unlocks the breech block, and on continuing the motion the block and carrier are swung into the loading position. The breech is opened by the cannoneer on the right seat pulling the hand lever toward him. The extractor, hinged to the right side of the breech, is automatically actuated in opening the breech, thus ejecting the empty cartridge case. The firing mechanism is so arranged that the gun can not be fired before the breechblock is home and the hand lever locked and is known as a continuous-pull mechanism. By means of the firing lever on the left side of the gun, operated by the gunner, the firing pin which seats in an axially bored hole in the breechblock, is cocked and fired by one continuous backward motion of the lever. The carriage has a tubular steel trail and axle, the rear end of the trail being fitted with a spade, lifting handles, trail eye, and traversing lever. The top carriage is provided with bearings, by means of which it is pivoted on the axle for traversing. Bearings are provided at the top to receive the cradle trunnions on which the cradle pivots. Longitudinal recesses are cut in the inner surface of the lower portion of the cradle for the reception of the guides on the jacket of the gun. A seat is provided on the left side of the trail for the gunner who sets the sights and fires the gun, and one on the right for a cannoneer who sets the range and operates the breech. 101 102 TJio ''Mi& ooTriar^ tojJ 1 fc,n*J' main shields and the apron are provided for the protection of the personnel against gun fire. The recoil cylinder is contained in the spring case in the upper por- tion of the cradle and is surrounded by two sets, inner and outer, of four sections each, of counterrecoil (running-out) springs, these being held under initial compression between an external flange on the front end of the recoil cylinder and an internal flange at the rear end of the outer spring case. The cylinder is attached and secured to the rear end of the gun by two nuts, while the piston rod with piston, which fits inside of the cylinder, is secured to the forward "end of the spring case. The piston rod is bored out for the reception of the counter recoil buffer which is secured in the rear end of the cylinder. Upon being fired the gun recoils, carrying with it the recoil cylin- der. The oil is forced to pass from in front of the stationary piston to the rear through grooves of graduated depth which set up an hydraulic resistance, thus checking the energy and bringing the gun to rest. In recoiling, the gun further compresses the two sets of springs which, after the gun has reached its maximum recoil, cause it to return to battery. The counter recoil buffer displaces the liquid in the rear end of the piston rod, the liquid being forced to escape over the tapered flats, thus resulting in the gun returning to battery without shock. A gravity tank is bolted to the front end of the recoil mechanism, which insures the cylinder being constantly filled, and is protected from gun fire by a shield. The angle of sight level is carried on a bracket riveted to the under- side of the rocking bar at the rear end and is adjusted by a leveling screw to which is attached a micrometer disc for setting off the angle of sight. The range indicator is fitted to the right side close to the handwheel and consists of a meter scale ring graduated on its face in hundreds of meters, the periphery of the ring being graduated in mils. The mechanism allows an elevation of 16 and depression of 5. The elevating gear is divided into two portions, upper and lower, and so arranged that the gun may be elevated or depressed without altering the line of sight. The traversing gear is pivoted to a bracket fastened to the trail at the rear end of the top carriage, and is operated by a handwheel extending out to the left side by means of which the gun may be traversed 72 mils right or left from center. A scale strip and pointer indicate the angle of traverse. Wooden wheels, 56 inches in diameter, are used, having steel tires 3 inches in width. Drag washers free to rotate about the hubs are secured by the dust cars. 103 104 105 The tire brake is for use in traveling, and is always used when firing. Brake arms are pivoted at one end to a bracket on the trail and have at their other end a cast-iron brake shoe which acts upon the tire of the wheel. The braking action is adjustable and brakes are operated by a lever having an eccentric link at its end. The sights used are the rocking-bar sight and panoramic sight, model of 1917, which are located on the left side of the carriage. Fixed ammunition is used in this 75-millimeter field gun and is made up of either common shrapnel or common steel shell. Shrap- nel rounds are issued with the projectiles filled and fuzed; the shells 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 shell. 75-MILLIMETER GUN MATERIEL, MODEL OF 1917 (BRITISH). A battery of British 75-millimeter gun carriages is accompanied by the following vehicles: 75-millimeter gun carnage limber, model of 1917, (British). 1 75-millimeter gun carriage limber, model of 1918. 1 75-millimeter gun caisson, model of 1918. 75-millimeter gun caisson limber, model of 1918. Forge limber, model of 1902 ML Store limber, model of 1902 MI. Battery and store wagon, model of 1917. Battery reel, model of 1917. This gun was formerly 3.3 inches in caliber but was modified to 75 millimeter giving interchangeability with French ammunition. All of this materiel used by the American Army was manufactured in the United States. The gun carriage limber, model of 1917, is of British design. 1 Either one of the above limbers may be issued. 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, however, fitted with wooden poles, which are more liable to breakage than steel poles; they have single draft hooks, instead of double trees for equalizing the pull on the braces; the pintle 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 readilv connected to the neck voke. 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. (106) 107 K I s VJ I 108 fc 109 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 110, can be used as an alternate for this vehicle. 75-MILLIMETER GUN CARRIAGE LIMBER, MODEL CF 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 160, 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 158. 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 (110) 1 1 1 REAR ViEVV OF LIMBER. 18322820 8 FRONT VIEW OF LIMBER. 112 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 provided 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. (113) 114 gfe g^ia i I 115 Standard 56-inch wheels are used and band brakes are provided. See page 158. 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 21 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 (116) 117 m flpf 2 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 necessary 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 mechanism consists of a handle pivoted vertically to provide hori- zontal 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. \Yhen 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 (118) 11!) ViEvV Ur CARRIAGE. REAR VIEW OF CARRIAGE. 120 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 cali- bers 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. Weight of projectile (filled and fuzed) pounds. . 15 Weight of cartridge case do 2. 25 Weight of fixed ammunition (1 round) do .... 18. 75 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 do 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 . . 15 Maximum angle of depression do 5 Amount of traverse of gun and carriage 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 1902 model in breech mechanism and the 1905 model is 50 pounds lighter in weight. The gun 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 breech block. 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 threaded and four slotted sectors. The breechblock is operated c <3 I (122) . ill ! ! " 1 124 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 se- cured 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 hydro-spring 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 125 12G Traversing is accomplished by means of a traversing shaft operated 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 necessarv . 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 158. The instruments provided for sighting and laying the piece include line sights, a rear sight, a front sight, a panoramic site, and a range quadran t. Three kinds of fixed ammunition are used in the 3-inch gun, models of 1902, 1904, and 1905, namely, common steel shell, common shrapnel, and high explosive shrapnel. Each round is issued with 127 1832282 128 129 projectiJes 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, 1902 or 1905 mounted on carriage, 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 manufacture. 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 doubletree and singletrees are formed of flange steel. Two doubletree rods each from the ends of the doubletree to the tie-rod (130) 131 clamps on the axle to which they are pinned. A pole prop is hinged 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 seat 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 Weight 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 .degrees. . 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. t 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. (132) 133 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 riveted. The chest is a rectangular flange steel box containing three ver- tical diaphragms supporting 70 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 W T eight 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. (134) 135 i rrypf^^ppi igilg-l rT^^E^c^ 13(5 CD 2? b CO co 61 ro 137 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, they being 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 J, 775 Rounds of ammunition carried in limber chest do 36 Diameter of wheels inches . . 56 Width of track I do. ... 60 Free height under limb'er . do 24 Turning angles with carriage degrees. . 80 Turning angle with caisson do 81 * Approximately. 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. RE\R 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. (138) 139 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 158. 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. . 75 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 24. 5 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 oilcans. SIDE VIEW OF STORE WAGON. The store wagon is intended primarily for carrying silch 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. See page 158. For detailed description and table of weights, dimensions, etc., see page 139. (140) 141 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 139. 142 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, 1 TOP VIEW SHOWING INTERIOR OF FORGE LIMBER. Shot fitting over the body of the chest to make it water-tight, 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 18322820 10 (143) 144 145 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 ], 106 Diameter of wheels inches. . 56 Width of track do 60 Free height under limber do 26. 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 160. The forge limber is used in connection with the American, British, and French 75-millimeter materiel, and the 3-inch gun 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 143. 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 Ml. The store limber, model of 1902 Ml, 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 160. For description and table of weights and dimensions, see preceding article on forge limber, model of 1902. STORE LIMBER, MODEL OF 1902 Ml. The limber is used in connection with the American, British, and French 75-millimeter materiel, and the 3-inch gun materiel, model of 1902. (146) 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 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. (147) 148 . ill! 149 The battery and store wagons are identical, except that the battery wagon carries a vise on the front end of the frame and a crow r bar bracket below the frame on the right side, and the store wagon con- tains packing strips and accessories for carrying a grindstone in the upper rear compartment. Standard 56-inch wheels are used. See page 158. 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. Weights, 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 width 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 4 miles of insulated cable, and in addition carries 2 steel chests containing 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. On the right side of the drum is secured a steel case in which a plotting board is carried. (150) 151 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 er gaged 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 1909MI, is issued in lieu of the battery reel, model of 1917, for motorized batteries. Weights, dimensions, etc. Overall length (tractioa pole removed) inc hes. . 74 Overall width do. ... 73. 75 Overall height do. ... 65 Weight of reel (without load) 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 Ml. The reel, model of 1909 Ml, is a two-wheeled vehicle designed to cany, 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 s 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. (152) 153 154 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 1909 Ml, together with the cart, model of 1918, is issued in lieu of the battery reel, model of 1917, for motorized batteries. Weights, 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 do .... 19 Turning angle with cart T 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. Tne forward end of the (155) 156 157 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 1909M1, 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. . 75 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. (158) 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. REEL FOR CAISSON, MODEL OF 1917, MOUNTED ON A CAISSON. The reel for caisson, model of 1917, is a hand-operated reel for the transportation and handling of telephone wires. 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 18322820 11 (159) 160 on the shaft of the spool. Chains are provided on either end of the frame for locking the cranks when not in use. 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. PIMTU BEMl.n* 6UIDC- '. , SICE* I ,FlNTlE KAHIN6 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 spring. 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. 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, with a muzzle velocity of 2,050 foot-seconds, a maximum range of 8,700 vards (7,900 meters) 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 25J 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 re- sistance 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. 061) 162 163 164 Tko 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.. 8 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 1G5 166 4.7-INCH GUN AND CARRIAGE, MODEL OF 1906. The 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. TRIGGER rORK CXTRKTOR rIH6 HHNOLC TRIP LHrcH PLUNGCR SHAFT RCTHIN1NS COLL a*eccM BLOC* TRI6SCR SH/trT OCTCN TIKIM6 MHOLC SHHTT 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. 167 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 hydro-spring 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 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. 168 169 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. Tho piece is elevated by a double screw type of mechanism. The upper end is attached to the cradle and so raises and lowers it. FRONT VIEW OF CARRIAGE EQUIPPED WITH BAND BRAKES. The screw is operated through gearing by two handwheels, one on 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 170 provided for supporting the trail when limbering. The spade can be released and folded up on the trail when traveling. 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 tires, and are equipped with band brakes. Some of the older type of vehicles have steel tires ELEVATING AND TRAVERSING MECHANISMS. and 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 quadrant. 171 172 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 gen eral. 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 BAND 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. 173 i_ uj $ V & & s ^ in ^ < o < S g < < I < r^ruuur< u inuminj^in^ r? 174 Fixed ammunition is used with this gun; shrapnel and high ex- plosive shell being used. The base fuzed stell shell and the shrapnel FRONT VIEW OF CARRIAGE EQUIPPED WITH TIRE BRAKES. weigh 60 pounds. The point fuzed sheel 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, forming, 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. 18322& 20 12 (175) 176 177 The doubletree, singletrees, and pole complete are omitted for motorized batteries and a competing pole is used in their place. The standard short pole with lunette is fitted for motor traction and for horss-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 principle 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 p6le to the socket. A prop of (178) 179 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 011 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. . : ' i Weights, dimension, etc. Weight of caisson limber, empty (without implements or ammunition), 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, 05J8 Weight of implements carried (including spare connecting pole) do. 147 Weight of caisson fully equipped and loaded do 4, 260 Hounds of ammunition carried in caisson limber 28 Rounds of ammunition carried in caisson 1 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. Tho limber is a two-wheeled vehicle provided with an ammuni- tion 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. Tho 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 bear- ings riveted to the sides of the chest and to the flanges of the inter- mediate plates. Tho 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 300 in the bearing, but is normally held in a vertical position by a spring bolted to the pintle bearing support. (180) 181 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 arc standard and interchangeable with those on any limber of the battery. Double- tree chains attached to the chest body prevent excessive movement of cither 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 RIGHT FRONT VIEW SHOWING CHEST DOORS OPEN EXPOSING DIAPHRAGMS. the fixed type of ammunition. The body is suspended in such a manner that 7 rounds are carried below and 21 above the axle. 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 carry- ing the usual complement of tools and accessories, also brackets for (182) 183 184 carrying fuze boxes on the outside of the chest. The chest provides scats 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 transformed 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 position. Suitable clearances are cut in the flange of each car- 185 tridge 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 whoii 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 a paulin that also 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 one mile of wire as for the caisson model of 1917. See page 159. Weight, dimensions, etc. Weight of caisson, empty with implements or 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 4, 812 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, brakes, 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 provided 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. Two 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, (186) 187 188 model of 1917, which is riveted to the top of the caisson and contains 1 mile of field wire so arranged that the "talk" goes through all the wire. See page 159. 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, GO 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 connsctor 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 ons 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 tlie constant recoil type, the recoil mechanism being of the hydro-spring 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. (189) 190 nl ag I 8 191 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 compression of the springs during recoil is sufficient to cause the gun to return 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 un adjustable connecter. The carriage permits elevation from 5 depression to 21 $ elevation. The carriage permits traverse of 4 left and 4 right, when it is ele- vated 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. 18322820 13 192 Weights, dimensions, and ballistics. Weight of carriage and gun pounds. . 12. 09 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 01 limber axle, approximately millimeters. . 4, 500 155-MILLIMETER GUN AND CARRIAGE, MODEL OF 1918 (FILLOUX). The gun, models of 1918 and 1918 Ml 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 breed i 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 breech block 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 breech block 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 lias 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 216, 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 elevating rack is bolted (234) 235 236 237 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 as the gun is elevated by means of an arm and gear sectors in such a manner as to shorten the recoil as the gun elevates. CARRIAGE IN FIRING POSITION. A replenisher or gravity tank is provided in connection with the recoil cjlinder 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. 238 239 The top carriage is a steel casting mounted on the bottom carriage, on which it pivots to traverse the piece. Belleville springs carry the weight of the gun when traversing, but on firing the springs compress and the firing stresses are taken on the bearing surfaces between the top and bottom carriages. The tipping parts are carried on the trunnions of the top carriage, which also houses the elevating and traversing mechanism and permits high angle of elevation for the cradle. The bottom, carriage is a steel casting suspended from the axle (in traveling position) by a heavy multiple leaf spring, j t supports the top carriage, houses the axle, and provides hinge connections for the trail. When firing the axle is unshackled from the springs and the bottom carriage bears directly on the axle. Traversing is accomplished by rotation of the top carriage on the bearing surface of the bottom carriage by means of a rack and train ACCESSORIES AND CATERPILLAR WHEEL SHOES. of gears which are operated by the handwheel on the left side of the carriage. A traverse of 60 30 right and 30 left is possible. Elevating is accomplished by a rack on the cradle operated through gears by the handwheel located on the gear box at the left of the top carriage. Elevations from to 35 are obtainable. The trail is of the split type and consists of steel plate beams of box section. Locks are pivoted at the forward end of the trails for securing them in the open position. When closed together they are clamped and attached to the limber. A traveling lock is provided on the trail for retaining the gun in retracted position. Two types of spade are provided, one for soft and one for hard ground. When traveling the spades are always removed from the trail. The wheels are of cast steel, each wheel having two solid rubber tires and are equipped with the usual band brakes. Caterpillar wheel shoes for traveling over soft ground are provided, which assem- ble over the rubber tires. They consist of 12 plates for each wheel, which give a broad bearing surface under the wheel. 18322820 16 240 241 The sighting equipment is exactly the same as that described under the 155-millimeter Schneider howitzer, except the difference in bracket as indicated on page 219. Ammunition used is of the separate loading type; the projectile weighs 95 pounds and the charge 25 pounds. Either shrapnel or high-explosive steel shell is used, as well as gas shells and other special ammunition. The propelling charge of smokeless powder is a sectionalized charge made up of two sections a base charge and one smaller increment. The fuses commonly used are the 31-second combination fuze for use with shrapnel and combining time and percussion elements the point detonating fuze Mark IV used with the steel high explosive shell, and the Mark II point detonating fuze used with gas shell. 155-MILLIMETER GUN CARRIAGE LIMBER, MODEL OF 1918 (FILLOUX). The carriage limber is a two-wheeled vehicle designed to support and secure the rear ends of the trails and to provide a coupling attachment to the tractor when transporting the carriage. The principal parts are the wheels, axle, steering mechanism, frame, springs, and seat. The axle is very similar to the usual design of front axles of auto- mobiles. It is of I-beam section, having forked ends with axle arms pivoted therein, providing a means of steering. By means of a drag- link and steering lever pivoted at the center of the frame and con- nected to the steel pole steering is accomplished. FRONT VIEW OF LIMBER EN ROUTE. The frame or clamp for holding the gun trail in position is mounted on the axle by means of two semielliptical multiple leaf springs. The upper cross beam of this frame has bolted to it a seat for the brakeman, who operates the gun-carriage brake when en route by means of a lever acting through a wire rope. The wheels are identical with and interchangeable with the wheels of the gun carriage. Weights and dimensions. Weight complete pounds. . 3, 190 Weight with carriage and gun do 23, 050 Weight of carriage on limber (traveling position) do 6, 490 Width of track (center to center of tires) millimeters . . 2, 250 Free height under limber and carriage (traveling position) do 250 Diameter of wheels do. ... 1, 160 Height of seat cushion from ground (seat assembled on top of trails, traveling position) millimeters. . 1, 550 Distance from center line of carriage axle to center line of limber axle (trails on limber) millimeters. . 4, 500 (242) 243 244 6-INCH GUN MATERIEL, MODEL OF 1917 (BRITISH). r n\c 6-inch gun materiel, model of 1917, is British throughout, being designed and manufactured in England. It consists of a 6-inch gun, Mark XIX, mounted on an 8-inch howitzer carriage, Mark VII, known as the 6-inch gun carriage, Mark VIII A. This Mark XIX gun is of wire-wound construction, having a muzzle velocity of 2,350-feet per second and a range of 17,500 yards. The gun body is of steel and consists of tubes, a series of layers of steel wire, jacket, breech bush and breech ring. The breech ring is prepared for the reception of the breech mechanism and is provided with a lug on the under side for the attachment of the hydraulic buffer and recuperator of the carriage. The breech mechanism is operated by means of a lever on the right side of the breech. On pulling the lever to the rear the breech screw is automatically unlocked and swung into the loading position. After loading, one thrust of this lever inserts the breech screw and turns it into the locked position. The breech mechanism is similar to that used on the 8-inch howitzers both in design and operation. The firing mechanism is of the percussion type and is not inter- changeable with other British guns. The firing mechanism is designed for percussion firing, and is so arranged that the gun can not be fired until the breech screw is locked and the breech mechan- ism ]ever home. The only changes necessary on the 8-inch howitzer carriages (p. 268) for mounting this 6-inch gun are: The rear extension plug, which connects the gun to the recoil mechanism, is modified and the cut-off gear is set differently to shorten the recoil when in action. The firing platform and all of the accompanying vehicles of the 8-inch howitzer materiel are used. Ammunition of the separate loading type is used, both shrapnel and shell being issued. Weights, dimensions, and ballistics. Materiel of gun, steel wire wound. Length of gun inches. . 219 Weight of gun with breech mechanism pounds. . 10, 248 Weight of gun without breech mechanism do 9, 940 Rifling, uniform one turn in 30 calibers. Weight of shell or shrapnel do 100 Weight of powder charge (maximum) do 23 Weight of powder charge (reduced) 15 pounds 7 J ouncea (245) 246 247 248 Maximum range: Full charge yards. . 17, 570 Reduced charge do 16, 100 Muzzle velocity: Full charge feet per second . . 2, 350 Reduced charge do 2, 000 Maximum elevation degrees. . 38 Weight of carriage (only) pounds. . 12, 548 Weight of gun and carriage (fully equipped ) do 22, 796 7-INCH NAVAL TRACTOR MOUNT, MARK V. The 7-inch naval tractor mount, Mark V, is a mobile, track-laying field piece bearing a 7-inch, 45-caliber naval rifle. Projectiles weighing 153 pounds may be fired at angle of elevation varying from horizontal to 40, and at the maximum elevation the extreme range obtainable is 24,000 yards. The chamber diameter of the gun is 8.5 and the distance from the face of the tube to the base of the projectile is 54.39 inches. The volume of the powder chamber is 3,369 cubic inches. The maximum charge consists of 60 pounds of smokeless nitrocellulose powder, which produces the maximum service pressure of 17 tons per square inch. Under these conditions a muzzle energy of 8,315 foot-tons is CARRIAGE AND LIMBER IN TRAVELING POSITION (FRONT VIEW). imparted to the 153-pound projectile, the muzzle velocity being 2,800 feet per second. The re ; coil mechanism is of the hydraulic type; the gun being re- turned to battery by a pneumatic counterrecoil system. The recoil 'system consists of a simple hydraulic brake, the energy of recoil is absorbed through a distance of 32 inches by forcing a mixture of glycerine and water through orifices of gradually decreasing diameter cut in the head of a piston operating in the recoil cylinder. The method of reducing the size of the orifices is interesting. The recoil piston has holes bored through it to allow the liquid to pass from one side to the other when the piston starts to move back when the gun is fired. Tapered throttling rods enter the holes in the pis- ton head, and as the piston moves back the size of the orifice is grad- ually diminished. The area of the orifices is so calculated that a constant retardation is given to the gun, and it is brought to rest at the end of the stroke. (249) 250 The counter-recoil mechanism adopted on this mount is similar to the counterrecoil mechanism of the French type, as used on 155- millimeter guns. In this type of mechanism when the gun is fired, a piston attached to the gun yoke moves backward in an air-tight cylinder containing air at a pressure of several hundred pounds per square inch, still further, compressing the air. The air pressure acting on the counterrecoil piston when the gun has reached the end of the recoil brings the gun back into battery or firing position. The counterrecoil system which is used on this mount is located on the top of the gun, and has been changed into a combination of three cylinders, connected at the lower end by a bronze head. The piston attached to the yoke operates in the central cylinder. The system REAR VIEW OF CARRIAGE. of liquid packing is retained but simplified and the entire system is made up of shapes and materials easily secured and is well adapted to American machining methods. A traversing gear, incorporated in the carriage trail, permits of limited training either side of the center line. When a greater range of training is desired, the trail is either shifted on the ground or the carriage is mounted upon a firing platform which provides for training through a firing angle of 60. A shell-loading tray, which rests on the carriage trail, is used to load shells into the breech. The elevating gear consists of a simple combination of a handwheel, worm gear, rack and pinion. The sighting arrangements for the gun consist of a standard panoramic field sight fitted to a bracket at- tached to the gun carriage. 251 The track layer, which is of the double-tread caterpillar type, is designed to carry the mount over practically any kind of ground likely to be encountered in service. The proportions of the chain tracks are such as to produce a pressure of about 14 pounds per square inch upon the soil during transportation, which is approxi- mately half that exerted by a horse. The track layer also serves as a stand or foundation for the mount during action. A caterpillar tractor is used to draw this vehicle from one position to another. A limber hooked between the mount and the tractor supports the trail during transit; during action the limber and the tractor are withdrawn from the immediate field of danger. The limber wheels are carried on taper axles and are equipped with grease cups for lubricating purposes. A pintle and lunette are pro- vided on the axle in case it is desired to attach an ammunition or supply trailer for transportation. The limber is connected to the LEFT SIDE VIEW OF CARRIAGE IN BATTERY. mount by means of a swivel pole end which is pivoted on the limber connection of the trail. The firing platform provides a durable and substantial foundation, adaptable to various soil conditions and light enough to permit of easy and convenient transportation. The firing platform includes a forward table, upon which the track layers rest, and a rear thrust beam to which the trail is secured by suitable pins. The rear thrust beam is made in two sections, which, when combined, provide for training through an arc of 60. One section may be used alone if desired. Training is accomplished by shifting the trail around the arc of the platform to the set of pin holes nearest the desired angle. Accurate adjustments in training are made with the traversing gear. The 7-inch naval tractor mount is so designed that its weight is almost entirely supported by the track layers, but a small percentage of the weight being carried on the trail. When the mount is being pulled along an upgrade of appreciable slope, the center of gravity 252 is shifted and the weight of the gun may have a tendency to throw the trail in the air. To preclude any such occurrence, eyebolts are secured to the gun yoke, which are used to draw the recoiling parts back sufficiently to bring about equilibrium. Track grousers may be bolted to the track shoes when there is likelihood of the mount slipping sidewise during transport on hill- sides. In an actual road test this gun was pulled over rough ground and proved able to negotiate any ground over which the tractor itself was able to operate. Obstructions were mowed down, and yet the entire weight of the gun was so evenly and well distributed that no damage was done to roads negotiated. The mount functioned per- fectly, remaining steady on the point of aim during continued firing. The caterpillar treads, locked in position by the brake, were as steady as a concrete foundation. 7-INCH GUN MARK II AND CARRIAGE MARK V. The 7-inch, 45 caliber, naval rifle is built up of a tube, hoops, and locking rings. When erosion destroys the effectiveness and accuracy of the gun it may be rebuilt by boring out the tube and shrinking in a conical nickel-steel liner. The gun, without the breech mechanism, weighs 12.81 tons, while the weight of gun and breech mechanism is 28,700 pounds. The rifling is right hand of hook section and consists of 28 grooves and lands, having an increasing twist from zero at the origin to one turn in 25 calibers at a point 22 inches from the muzzle. The remainder of the twist is uniform. This gun is the heaviest and hardest hitting gun for which a mobile lield mount has been requested bv our Army. CARRIAGE AND LIMBER IN TRAVELING POSITION (REAR VIEW). The carriage, which supports the gun is a structural steel frame- work built up of standard shapes, consisting essentially of two steel trunnion bearing plates cross braced at each end to form a single unit with a central well into which the gun recoils. These side girders are riveted to the carriage trail, the carriage and trail forming a rigid unit, are supported on the carriage axle which turns in hubs mounted in the truck frames of the track layer. On the left-hand side of the carriage is arranged the mechanism for elevating and depressing the gun. The traversing gear, which provides means for training 2 either side of the center line, is incor- porated in the rear section of the trail. This gear consists of a steel plate resting on the ground underneath the trail: a worm shaft oper- (253) 254 ated by ratchet wrenches shifts the trail with reference to the plate and enables the gun to be accurately trained. Navy guns do not carry the trunnions attached directly to the gun, but are turned to a smooth surface on the outside. The cylindrical gun slide, on which the trunnions are attached, carries the gun; the trunnion seats are placed at the upper end of the carriage. The recoil and counterrecoil mechanisms are also attached to the gun slide, operating through pistons atttached to the yoke. The gun runs in and out of the gun slide when recoiling, bronze liners being fitted to the inside of the slide to enable this to take place easily. The trunnions of the gun are mounted sufficiently high so that at maximum angles of elevation only a shallow trench need be dug to permit clearance for the recoil of a gun. TOP CARRIAGE AND AXLE DETAILS. The elevating arc segment, meshing with the pinion of the eleva- ting mechanism, is bolted to a pad on the left-hand face of the slide. The teeth of the arc are cut on a pitch circle concentric with the trunnion centers to permit of a 40 movement of the slide in a ver- tical plane, starting from horizontal. The upper and lower extremi- ties of the arc are fitted with limiting stops to prevent j amming. The hydraulic brake. The energy of recoil is checked and dissipa- ted by means of a hydraulic brake mounted on the bottom of the slide. This mechanism is made up of a piston operating in a cylinder filled with liquid and rigidly fixed to the slide. The piston is attached to the gun yoke by the piston rod which passes through a stuffing box in the rear end of the cylinder. Two orifices are provided in the piston head for throttling rods w^hich are arranged longitudinally in the cylinder. In battery, all the liquid is in rear of the piston. As the piston recedes during recoil, the liquid is forced around the throttling rods through the orifices in the piston to the forward end 255 of the cylinder, dissipating the erffergy through the frictional heat generated. The cross section of the throttling rods, around which the liquid must flow in passing through the orifices, is such that a pressure approximately uniform is exerted upon the liquid throughout the period of recoil. The length of recoil is 32 inches. . Incorporated in the cylinder head is a counterrecoil chamber into which the recoil liquid flows during recoil. When the gun is brought back to battery by the counterrecoil mechanism, its momentum is ASSEMBLED VIEW OF HYDRAULIC BRAKE. checked through the action of a counterrecoil plunger, mounted on the forward face of the piston, as it enters the chamber and forces the liquid back into the cylinder through the orifice between the plunger and the plunger bushing screwed into the mouth of the cham- ber. This action takes place during only the last 14 inches of coun- terrecoil stroke. The liquid used in the hydraulic brake consists of a mixture of 4 parts glycerine and 1 part water, by volume. This liquid is poured into the cylinder through a filling hole on the right-hand side of the cylinder head. 18322820 17 256 The upper portion of the cyliiuter head is arranged to form an ex- pansion chamber to provide for the expansion of the liquid which results from the f fictional heat generated in the cylinder. When expansion of the liquid takes place with continued firing, the increased volume of the liquid simply compresses the air in the expansion chamber instead of acting to prevent the return of the gun to battery. To assure the presence of a definite amount of air in the expansion chamber at all times, the filling hole is fitted with a tube which extends down into the chamber and traps the desired volume of air when the cylinder is filled. Counterrecoil system. Energy to return the gun to battery and to maintain it in that position at all angles of elevation is obtained by means of a pneumatic counterrecoil system, mounted on the top of VIEW OF AXLE MOUNTED IN TRACK LAYER. the slide. A piston, operating in an air cylinder and connected to the gun yoke by a piston rod, serves to compress the air within the cylinder when the gun recoils. At the end of recoil, the compressed air acts upon the piston to return the gun to battery. On either side of the air cylinder and connected with it through a port is an air tube which serves as a reservoir. Since it is necessary for the counterrecoil system to support the weight of the gun and breech mechanism against gravity, the system is charged initially with air at 300 pounds per square inch, gauge pres- sure. This pressure assures the proper functioning of the counter- recoil mechanism at angles of elevation up to approximately 34. It is apparent that the factor of gravity decreases with the angle of elevation and hence less pressure is required to bring the gun to bat- terv when it is fired at angles near horizontal. 257 When charged to 340 pounds pressure, the mechanism will func- tion properly at all angles; however, if the cylinder should be charged only to, say, 225 pounds, the mechanism may be relied upon to return the gun to battery at angles of elevation up to 23 or 24. To insure return of the gun to battery when firing at angles above 34, air cylinders should be charged in accordance with the instructions, and to prevent breakage of the gauge glass and to preserve the accuracy of the instrument, it is recommended that the pressure gauge be removed before firing. The elevating gear train from the rack on the slide to the handwheel on the left side of the trail is made up of a pinion and shaft in mesh with the elevating arc. One turn of the elevating handwheel moves the gun 56' 17" in elevation or depression. The axle, a steel forging extending across the width of the carriage is supported in the track layer by a hub bracket which in turn is carried by the structure of the girder on which the sprocket and truck L SIDE ELEVATION OF TRACK LAYER. wheels are mounted. This bracket is held by oscillating bearings and is spring supported so that the caterpillar may adjust itself to any unevenness in the road when the gun is in motion. When the gun is placed in firing position, the springs are taken up by means of holding down screws in order that the mount may keep steady on the point of aim while firing. The function of the hub springs is to impart to the mount a degree of resiliency during transit. However, when firing, resiliency in the mount is undesirable and often dangerous, thus before firing the springs are compressed until the hubs bear directly upon the truck frames. This is accomplished by means of adjusting screws screwed down on the hub bearing blocks until the springs are compressed and the hubs rest solidly upon the truck frames. The trade itself consists of an endless belt of cast steel links connected by hardened pins, each link carrying a corrugated forged-steel plate which makes contact with the ground. The plates overlap when horizontal so that a continuous surface is presented. To prevent the 258 corrugated surface of the tread from slipping in soft ground, de- tachable grousers are provided. The track links run over a large idler wheel, a sprocket wheel, seven truck rollers, and four track rollers on each caterpillar track layer. The sprocket wheels carry but little of the load except when the gun is descending a grade or when the brake is applied to the mount. For smooth running and reliability, roller bearings are fitted in the truck and idler rollers, the ends of the rollers being closed by steel plates to prevent the entrance of dirt when the mount is hauled through mud, sand, or soft earth. A brake is provided to permit control of the mount when descending hills and also to lock the cater- pillar in position when the gun is set up for firing. The brake con- sists of a toggle joint operating on the rim of one of the sprocket wheels, the tension applied being controlled by an adjustable spring. CARRIAGE IN BATTERY POSITION, SHOWING MAXIMUM ELEVATION OF GUN. Simple as the brake is it has been exceedingly satisfactory in opera- tion in controlling the heavy mount on steep grades and in checking any tendency of the mount to move on firing. The track is carried around two track idler wheels which are pro- vided with bearings mounted on the extremities of the track frame. The aft idler wheel bearings are so mounted that they may be moved backward or forward as necessary to adjust the tension and to take up wear on the links and shoes. Friction brakes operating against the forward idler wheels are mounted on the truck frames. These brakes are of the spring release type and are applied by means of handwheels functioning through yokes and levers to the brake shoes. The quadrant sigJit (Schneider} is mounted on the left trunnion of the carriage both in traveling and in action. 8-INCH HOWITZER MATERIEL (VICKERS). Success has been obtained with the 8-inch howitzer artillery for preliminary bombardment which precedes an infantry attack. This caliber is mobile in a sense, but there are limits to its mobility, for there comes a time when its advance must stop. When these howitzers have to be transported over land full of huge craters r with the roads entirely destroyed, the country encumbered with all kinds of debris and frequently reduced to a sea of mud, it can be easily seen why a successful "push" usually nets a considerable gain in captured artillery. If the trenches give way, it is almost impossible to get the heavy howitzers away quickly enough to save CARRIAGE IN BATTERY POSITION. them from being captured by the enemy. Thus, by mobile artillery is meant that which can be moved around essentially as part of the infantry. The howitzer, being comparatively thickset and short when com- pared with a gun of the same .caliber, is capable of greater angle of elevation than the same caliber of gun. The gun is primarily intended for attacking troops, while the chief aim of the howitzer is to destroy incumbrance such as trenches, barbed wire, pill boxes, and the like. A shell that travels from the howitzer ascends at a high angle and drops almost vertically. The explosion of a shell so fired is much more effective than one that is fired with only a slight elevated trajectory, as in the case of the field gun. (259) 260 261 The 8-incli howitzer, being mounted on a wheeled carriage and not having to he disassembled for transportation, is much more mobile than the 9. 2-inch or 240-millimeter howitzer. This howitzer when set up ready for firing rests on and is braced upon a firing plat- form, which is transported on a two-wheeled wagon, the wagon being attached to the howitzer carriage and drawn as part of the unit with the carriage and limber by a tractor. On reaching the spot selected for position the firing platform is buried flush with the surface of the ground, furnishing a steady emplacement from which to fire. The 8-inch howitzer materiel is called the "Vickers" model of 1917, of which there are in use two types, the Mark VI and Mark VII. The main differences between the Mark VI and the Mark VII being that the former has a lower muzzle velocity and consequently a shorter range than the latter, also that the Mark VII has a barrel of the "wire wound" construction, whereas the Mark VI type is of the "built up" construction. The Mark VII is also longer and heavier than the Mark VI. The Mark VII has lately been superseded by a Mark VIII^, the difference between the two being that the powder chamber walls of the Mark VII proved to be too thin, while the Mark VIII^ overcomes this defect by having thicker powder chamber walls. Due to the fact that the Mark VIIIJ howitzer has a greater muzzle velocity, and consequently a greater maximum range than the Mark VI by some 15 to 20 per cent, the former is the preferred type. The life of the howitzers before relining is necessary varies greatly. 'Hie number of rounds they are capable of firing before the lining becomes badly worn depends on whether light or heavy propelling charges are used. The use of light propelling charges and greater trajectory elevation to get the desired range is recommended rather than heavy charges and low elevation. From information based on actual experience the average life of the 8-inch howitzer, Mark VI, is 7,800 rounds, while that of the Mark VHIi is 3,000 rounds. Comparative table of weights, dimensions, and ballistics for 8-inch hoivitzers, Marks VI and Vlin and 6-inch gun, Marie XIX. Mark VI howitzer (Mark VT Mark VIII* howitzer (Mark Mark XIX VII VIII-A carriage). carriage). Weight of howitzer or gun, including breech mechanism.. Weight of gun or howitzer without breech mechanism Total length of howitzer or gun Length of howitzer or gun .pounds.. do ..inches., calibers 6,552 6,132 127.6 15 9 7,730 7,310 148.3 18 5 10,248 9,940 219.22 36 5 Distance to center of gravity from breech, unloaded . . inches 42.6 50.5 71 95 Distance to center of gravity from breech, loaded do 42 3 50 6 71 65 Length of bore. do 117 7 138 4 210 Length of bore 14 7 17 3 35 Length of rifling... ..inches.. 102. 11 99.52 170. 75 262 ~ * 263 Comparative table of weights, dimensions, and ballistics for 8-inch howitzers, Marks VI and VIII\ and 6-inch gun, Mark XIX Continued. Mark VI howitzer (Mark VI carriage). Mark VIIIJ howitzer (Mark VII carriage). Mark XIX gun (Mark VIII-A carriage). Number of grooves 48 48 36 Twist (uniform) R. H Iinl5 Iin25 lin 30 Travel of projectile in piece inches.. 104. 96 102 72 174.0 Weight of projectile Weight of powder charge pounds . . do 200 10.75 200 17.5 100 23.0 Max imum powder pressure . . . ...do.... 30,250 30,240 Muzzle energy foot- tons 2 345 3,228 3,308 Muzzle velocity . feet per second. . 1,300 1,525 2,350 Length of recoil inches. 60-24 52-24 42-20 Maximum elevation degrees. . 50 45 38 Range at 15 degrees elevation Range at 20 degrees elevation yards., .do 6,430 7 S10 7,400 8,900 11,300 13,100 Range at 25 degrees elevation ...do... 8,920 10,500 14,600 Range at 30 degrees elevation . . .do .. 9,800 11,540 15,960 Range at 45 degrees elevation do 10 710 12 300 do 10 760 12 360 17,5CO The Mark VI howitzer has a muzzle velocity of 1,300 feet per second and a maximum range of 10,760 yards and is of British design and of both British and American manufacture. The Mark VII howitzer has a muzzle velocity of 1,525 feet per second and maximum range of 12,280 yards and is of British design and manufacture. The Mark VIII| is an American modification of the British wire- wound Mark VIII howitzer to permit of a built up type of construc- tion and is strictly of American manufacture. The Mark VIIIJ has the same muzzle velocity and range as the Mark VIII. Due to the combination of British and American manufacture, there are several types of breech mechanism in service; the two main types are the T and the French percussion type. The three types of carriages differ but slightly in design. Each is a two-wheeled vehicle with a box-shaped trail, the latter being cut away to provide clearance for the recoil of the howitzer or gun when fired at high angles of elevation. The trails of the Mark VII and VIII-A types are modified to provide a larger clearance to accommo- date the Mark VIII^ howitzer and Mark XIX gun (see p. 246) and are also strengthened to withstand the greater energy of recoil. The howitzer is mounted in a cradle in which it is free to recoil under the control of a hydraulic recoil cylinder. After recoil it is returned to firing position by means of a pneumatic recuperator. The carriage permits of firing at high angles of elevation, and as the elevation is increased the length of recoil is proportionally decreased by a cut-off gear fitted to the cradle and buffer in order that the howitzer will not strike the trail or ground when fired. The recoil mechanism is of the hydropneumatic type with a variable recoil mechanism which lessens the length of recoil the greater the elevation given the howitzer or gun. The liquid used in the mechanism is British buffer oil. 264 The elevating mechanism permits a movement of 50 maximum ele- vation for the Mark VI carriage, 45 for the Mark VII carriage, and 88 for the Mark VIIIA carriage. The cradle pivots on its trunnions and rests in bearings provided in the top carriage, which in turn is pivoted at its front center to a transom on the trad in such a manner that it is free to rotate under REAR VIEW OF CARRIAGE, SHOWING MAXIMUM ELEVATION OF HOWITZER. control of the traversing gear, 4 to the right or 4 to the left of the center line of 'the trail, a total of 8 traverse for each of the three types. A quick-loading gear is fitted to the cradle for bringing the howitzer rapidly to the loading position (7 30' elevation) after firing, and vice versa. The trail is composed of two side members supported at the front end of the axle and terminating in a spade at the rear end. Screw brakes for use in firing or traveling are fitted to either side at the for- ward end of the trail. A traveling lock is provided on the trail to lock the trail and cradle together to prevent strains on the elevating and traversing mechan- isms when traveling. 265 The wheels are made entirely of steel and have wide 1 ires fitted wil li steel cleats to ensure good traction. The sighting gear is composed of a rocking bar sight with panoramic, sight and clinometer for the usual method of sighting and a dial sight for the quick laying of the piece. RIGHT SIDE VIEW OF CARRIAGE IN BATTERY. Comparative table of weights and dimensions of 8-inch howitzer carriages, Marks VI and VII, and 6 -inch gun carriage, Mark VI II- A. Mark VI. Mark VII. Mark VIII-A. Weight of carriage (only) Weight of carriage, limber, and howitzer or gun Weight behind team, heaviest load pounds.. do.... do 12,548 21,700 29,540 19, 100 528 54.0 "76.6 685 1,008 60 69 95.8 !4 right 4 left 26 right 26 left 66 12 76 256.5 260 12.320 22,650 30,490 20.050 532 64.8 1.700 76.8 749 1,859 60 69 95.8 4 right 4 left 26 right 26 left 66 12 76 276.5 280 12,548 25,110 32,950 22,796 Weight of howitzer or gun carriage in firing position Weight at end of trial do.... do Volume of liquid in recoil cylinder Volume of air in recuperator cylinders Volume of liquid in recuperator cylinders Initial pressure " poun< .'.pints. . cu. in.. pints.. Is per sq. in.. 64.8 1,693 76.8 740 1;678 60.5 Maximum air pressure Height of bore above ground inches . . do Width of carriage over axle . do 95.8 4 right 4 left 26 right 26 left 66 12 76 322.5 325 Angle of traverse degrees., do Diameter of wheels inches . . Width of tires carriage rin Width of track, center line to center line of wheels do Maximum length of carriage, firing position (howitzer or gun hori- Maximum length of carriage, traveling position (howitzer or gun horizontal) innhAs The carriage limber is made of steel and has wide steel-tired wheels. At the rear is* a limber hook which engages the lunette at the trail end of the carriage. A chest is mounted on the limber, providing seats for the personnel, and fittings on the interior for carrying tools. The limbers which were manufactured in England have wooden chests, while those manufactured in America have steel chests. A connecting pole provides for motor transportation when traveling, the units being arranged in the following order: Limber, gun or howitzer carriage, and platform wagon, which combination is drawn by a tractor. 266 These types of carriages are provided with a platform by means of which a traverse of 26 right and 26 left is obtainable. The plat- form is used whenever conditions and time permit emplacement. For transportation the platform is disassembled and placed- on a transport wagon, which consists of two wheels and an axle, to which the parts of the platform are securely clamped. Eight-inch howitzer materiel (British) consists of: Model of 1917 (Vickers Mark VI and Mark VII). Model of 1918 (Vickers Mark VII). Limber, model of 1917 (Vickers). Firing platform and wagon, model of 1917 (Vickers). The 8-inch howitzer materiel, model of 1917 (Vickers Mark VI) , consists of: Carriage, model of 1917 (Vickers Mark VI). Howitzer, model of 1917 (Vickers Mark VI). Limber, model of 1917 (Vickers). Firing platform and wagon, model of 1917 (Vickers). The 8-inch howitzer materiel, model of 1918 (Vickers Mark VII) , consists of: Carriage, model of 1918 (Vickers Mark VII). Howitzer, model of 1918 (modified from Vickers Mark VIII to United States Mark VIIIJ). Limber, model of 1917 (Vickers). Firing platform and wagon, model of 1917 (Vickers). The above materiel is of British design and of both British and American manufacture. 267 * s B I s 8-INCH HOWITZER AND CARRIAGE (BRITISH). The Marie VI howitzer is of the built-up-construction type and consists of a tube over which is shrunk a jacket. Front and rear guide rings provide means of supporting the howitzer in the cradle. A breech ring is also shrunk on for additional strength and carries a lug for connecting the gun to the recoil mechanism, and a breech bushing is provided for reception of the breechblock. The total length of this howitzer is about 10 J feet and its maximum range is approximately 10.760 yards; this howitzer is mounted on the Mark VI carriage. REAR RIGHT SIDE OF CARRIAGE IN FIRING POSITION. The Mark VI 11$ howitzer is also of the built-up-construction typo, but differs from the Mark VI howitzer in that it consists of two tubes, an inner and an outer, over which is shrunk the jacket. The jacket in this case supports the howitzer without the use of guide rings. A breech ring is shrunk on over the jacket and carries a lug for connect- ing the gun to the recoil mechanism. A breech bushing similar to that of the Mark VI is fitted for the breech mechanism. The total length of this howitzer is about 12 i feet and its maximum range is approximately 12,360 yards. This howitzer is mounted on the Mark VII carriage. (268) 269 270 271 The breechblock is of the interrupted-screw type. It is operated by a lever on the right-hand side of the breech, which by one motion releases the screw threads and opens the breech, or vica versa, on closing. The forward mushroom-shaped head of the breechblock is equipped with a flexible asbestos ring, known as the obturator pad. On firing, this ring is compressed and acts as a gas check to prevent the leakage of powder gases back through the breech. It has sufficient resili- ency to resume its original form after firing, as described on page 216. For firing the charge, two separate types of igniters or primers are used. The one known as the T tube consists of a. small T-shaped copper tube which fits into a suitable socket in the breech; it is fired by pulling a friction wire out of the tube by means of a lanyard. The BREECH BLOCK. other type, the percussion primer, is very similar in construction to a blank rifle cartridge. It fits a percussion firing mechanism on the breech which fires the primer by means of a hammer operated by the lanyard. This mechanism is common and interchangeable with the 155 millimeter gun and howitzer; also the 240 millimeter howitzer. Howitzers fitted for one type of primer will not permit the use of the other type. Both types have a safety lock, which prevents firing when the breech is not entirely closed. The recoil mechanism is of the hydropneumatic long-recoil type and contains both recoil brake and recuperator. The recoil mechanism is an hydraulic brake to absorb the energy of recoil of the piece. It consists of a piston rod and piston traveling in an oil-filled cylinder. The piston rod is connected to the cradle 18322820 18 272 273 which remains stationary while the howitzer recoils. 'Die cylinder block is connected to a lug on the howitzer and recoils with it so that when the gun is fired the piston is forced against the oil in the cylinder. Ports are provided in the piston to permit of the passage of some of the oil. At the beginning of the recoil a large quantity of oil is per- mitted to pass, but as the howitzer further recoils a valve on the piston rod, operated by lugs sliding in spiral grooves in the cylinder walls, gradually closes the port so that no oil can pass and the howitzer is brought gradually to rest. FRONT VIEW OF HOWITZER CARRIAGE. In order to prevent the gun striking the ground when firing at high elevation, a method is provided for automatically closing the piston valves sooner as the elevation increases, thus shortening the recoil. The mechanism which accomplished this feature is known as the valve turning gear. The rear end of the piston rod is extended and so designed that it forms a counterrecoil buff er when it enters a suitable chamber bored out in the buffer plug. This buffer prevents violent return into firing position after recoil. The recuperator or counterrecoil mechanism serves to return the howitzer to firing position after recoil. It consists of two liquid cyl- 274 inders which are connected in turn with two air cylinders. On recoil- ing, the recuperator pistons force the oil out of the recuperator cylin- ders into the air cylinders, thereby highly compressing the air. When this air expands to its original volume it drives the oil back against the recuperator pistons, thereby returning the howitzer to firing position. The recuperator also acts as an auxiliary recoil buffer, absorbing up about 10 per cent of the energy of recoil. The air in the recuperator is maintained at a pressure of about 700 pounds per square inch in order to prevent the howitzer slipping back on the cradle at high elevations. A suitable pump is provided with the mate- rial for maintaining this air pressure. ELEVATING AND TRAVERSING MECHANISM. The carriage consists of a top carriage, cradle, trail, wheels with axles, and the elevating and traversing gear. The Mark VI and Mark VII carriage are similar in design and differ only in that Mark VII has a slightly larger recoil mechanism and the trail is cut out somewhat to allow for the greater length of the howitzer recoil. The top carriage is built up of nickel-steel plate and carries the trunnion bearings for the cradle. It is pivoted in the front transom of the trail, so as to permit the necessary traverse. The cradle which carries the recoil mechanism and provides slide ways for the recoil of the howitzer when in action, is supported by the trunnion bearings of the top carriage. 275 276 277 The trail is of the solid type, cut out to provide clearance for the howitzer to recoil. The spade is removable and the shoe or bracket may be substituted when firing on scotches or using the firing plat- form. The elevating and traversing gears are operated by handwheels on the left side of the carriage. The Mark VI carriage permits of an elevation of 50; the Mark VII, 45; and the Mark VIII-A, 38. Both carriages permit a traverse of 8. A quick-loading gear is provided to allow the gun to be brought rapidly to loading position when firing at high angles of elevation. The wheels are ol the all steel wide- tire type, 66 inches in diameter with tires 12 inches wide. They are fitted with brakes which act independently on each wheel. Sighting is accomplished by means of a rocking-bar sight supple- mented by a panoramic sight. These are located on the left SKU *.> the piece and serve to lay for elevation and traverse respective^. A dial sight is provided on the right side of the piece for quick laying. Ammunition of the separate loading type is used with the 8-inch howitzer. Shell issued is of the high-explosive type only and weighs 200 pounds. These are issued filled but not fuzed and are fitted with a booster and adapter. Fuzes of types to suit different conditions of firing are provided, giving delayed or instantaneous action. The propelling charge is contained in cloth bags and is made up of separable increments, permitting various zones of fire. The maxi- mum charge for the Mark VI howitzer weighs 10.8 pounds; for the Mark Vlllf howitzer, 17.5 pounds. Separate loading ammunition is used in the 6-inch gun mounted on a Mark VIII-A carriage. The original British ammunition so closely resembled the American that it was decided to use the regular Mark II high-explosive shell. Each round is issued with the projec- tile filled, also the adapter and booster in place. The fuze hole in the adapter is fitted with a white metal plug. The weight of the projectile complete is 90.33 pounds. The propellant charge will consist of a base section and increment section having a total weight of approximately 25 pounds. 8-INCH HOWITZER CARRIAGE LIMBER, MODEL OF 1917 (VICKERS). The limber provided with this and for the 6-inch gun materiel is of steel construction and provides a chest for tools and spares, also seats for the personnel. No ammunition is carried in this limber, but two types of poles are provided, a long one for horse-drawn vehicles and a shorter connecting pole for motor traction. The box or chest of limbers manufactured in England is of wood and is bolted to the top of the rails. The lid is covered with water- proofed canvas and hinged at the front. Those limbers which were manufactured in the United States are provided with steel chests which vary slightly from the wooden chests in fittings provided for tools and accessories. The axle is cylindrical in shape and fitted with special axle arms. It passes through bearings formed in the rails and is held in position by brackets. The top of the chest is equipped with guard irons and blanket straps, receptacles being provided on the sides and ends to take an ax, a shovel, and other implements. The interior of the chest is fitted to carry tools, spare packings for buffer and recuperator, and other necessary stores. Clips are secured at the front of the chest to accommodate two rifles, used in emergencies when attacked en route. The wheels are 66 inches in diameter and have a tire 6 inches in width with rounded edges. Weights and dimensions. Length of wheel base, limber, and carriage (limbered) inches. . 187 Overall length of limber, carriage, and firing platform wagon (tractor draft) inches. . 550 Turning angle degrees . . 40 Weight of limber, empty pounds . . 2, 160 Weight of limber, fully equipped and loaded do 2, 600 Diameter of wheels inches.. 66 Width of tires do 6 Width of track do. ... 82 Weight of each wheel pounds. . 554 Number of men carried 3 (278) 279 280 8-INCH HOWITZER FIRING PLATFORM AND WAGON, MODEL OF 1917 (VICKERS). A wooden firing platform is provided on which the carriage of the 8-inch howitzer and 6-inch gun materiel can be mounted when suf- ficient time is permitted for setting up. The platform consists of wooden beams which assemble to form a triangular platform. The spade must be removed and a special bracket fitted on the trail when using this platform. This bracket travels in a groove which gives a bearing for the bracket and also provides a means of travers- ing the piece 52 on the platform. The platform is disassembled and mounted on a pair of wheels and axle for transportation. The main objects in the use of the firing platform are: To provide a reliable suppport for the wheels and rear end of the trail, so as to prevent sinking or movement when firing on soft ground; to insure the gun remaining on the target when firing; and to provide means for shifting the trail transversely through an angle of 52 (26 each side of center). By using the traversing gear on the carriage a total traverse of 30 on each side of the center is obtainable. The firing platform is composed of a support upon which the wheels of the carriage rest, two side beams hinged together at the forward end and a rear beam made in a top and bottom section. These com- ponents form a triangular-shaped frame upon which the carriage may be placed when firing. The support for the carriage wheels is placed near the apex of the triangle formed by the hinged side and rear beams. The rear beams form the base, the upper one being curved at its front edge to form a guide for shifting the trail. The carriage wheels rest on steel plates on the wheel platform and are guided by curved-steel angles which prevent lateral movement of the gun off the target when in -action. When the firing platform is used, the float plate, with spade attached, which is bolted to the underside of the trail, is removed and another float plate, having a thrust bracket attached, is bolted in its place. In traveling the units of the 8-inch materiel are arranged in the following order: Limber, carriage, and platform wagon. The usual plan is to draw this combination by a tractor. (281) 282 Weights and dimensions. Overall length of wagon (traveling position) inches. . 240 Overall height of wagon do 66 Overall width of wagon do 105 Diameter of wheels do 66 Width of tires do .... 6 Width of track do 85 Road clearance do 18 Weight of platform pounds. . 5, 740 Weight of wood platform and wagon (complete) do .... 7, 840 Weight of steel platform and wagon (complete) do 9, 630 9.2-INCH HOWITZER MATERIEL (VICKERS). The 9.2-inch and 240-milliineter howitzers are the largest weapons of the mobile type in service by the American Army at the present time. While these calibers are mobile in a sense, yet there are limits to their mobility, for when these howitzers have to be transported over land full of huge craters, with the roads entirely destroyed, the country encumbered with all kinds of de*bris, and frequently reduced to a sea of mud, one can realize just why a successful attack usually nets captured artillery, and on the other hand, if the trenches give way, it is rather difficult to got these heavy howitzers away quickly enough to save them from being captured by the enemy. Both types of 9. 2-inch howitzers are practically similar in all features, both being platform mounts as illustrated. These units break up into three separate loads for traveling, the howitzer proper forming one load, the top carriage and cradle the second load, and the platform the third load. The Mark I type of howitzer is 13 calibers long, while the Mark II type is 17.3 calibers, the principal difference being that the latter model is a more powerful weapon. Both types are provided with an earth box which is secured on firing beams, and in which the earth excavated for the firing beams is thrown; the additional weight gives greater stability when firing. The recoil mechanism is of the variable type which limits the amount of recoil according to the elevation, the recoil cylinder being fitted with a counterrecoil buffer to control the return of the howitzer into battery. A gravity tank insures that the recoil cylinder will at all times be filled with oil, but will provide the proper amount of void for expansion of the oil in the cylinder. The counterrecoil mechanism is of the pneumatic type consisting of a cylinder, a piston with rod, and a floating piston. The floating piston separates the oil and air chamber and the rod extending through the oil chamber provides a differential pressure and effects a seal, pre- venting the air leaking into the oil chamber. The operation of the howitzer in firing is that the recoil cylinder and the counterrecoil, or recuperator piston rod, move to the rear with the howitzer, the recoil piston rod and the recuperator cylinder remaining stationary. The flow of oil in the recoil cylinder past the piston rod and valve limits the length of the recoil and the com- pression of the air in the recuperator cylinder is sufficient to return (283) 284 285 it to battery after the force of the recoil has been absorbed. The counterrecoil buffer in the recoil cylinder limits the counterrecoil of t he howitzer and allows the piece to return to battery position with- out shock. The howitzer, being comparatively thickset and short when com- pared with a gun of the same caliber, is capable of greater angle of FRONT VIEW SHOWING MAXIMUM ELEVATION OF HOWITZER. elevation than the same caliber of gun. The gun is primarily in- tended for attacking troops while the chief aim of the howitzer is to destroy incumbrance such as trenches, barbed wire, pill boxes, and the like. A shell that travels from the howitzer ascends at a high angle and drops' almost vertically. The explosion of a shell so fired is much more effective than one that is fired with only a slight ele- vated trajectory as in the case of the field gun of the same caliber. 286 From information based on actual experience, the 9.2-inch how-, itzer, Mark I type (low velocity), has an average life of 8,300 rounds, while the Mark IT (high velocity) has an average life of 3,500 rounds. The howitzer transport wagon is a four-wheeled vehicle the body of which contains a winch for removing and mounting the howitzer in the cradle. This vehicle is equipped for motor traction and has brakes acting individually on each hind wheel. The carriage bed (or platform) transport wagon is formed by fixing a front and rear axle to suitable attachments on the bed, thus forming the body of the wagon. Attachments are provided for brakes which act independently on each hind wheel and connections for attach- ment behind the howitzer transport wagon. LOADING POSITION OF HOWITZER, SHOWING SHELL ON TRAY. The top carriage transport wagon is formed by attaching two axles with wheels to the top carriage, which forms the body. Individual brakes are fitted on the hind wheels. This vehicle is usually coupled behind the platform wagon. The three wagons are drawn en train by tractor but may be hauled singly in case of necessity. The 9.2-inch howitzer materiel (Vickers), Mark I, consists of: Howitzer carriage, model of 1917. Howitzer platform transport wagon, model of 1917. Howitzer carriage transport wagon, model of 1917. Howitzer transport wagon, model of 1917- The 9.2-inch howitzer materiel (Vickers), Mark II, consists of: Howitzer carriage, model of 1918. Howitzer platform transport wagon, model of 1918. Howitzer carriage transport wagon, model of 1918. Howit/er transport wagon, model of 1918. 287 1S3228 20 19 9.2-INCH HOWITZERS AND CARRIAGES, MARKS I AND II (BRITISH). This materiel is designed to be transported in separate loads, thus three four-wheeled vehicles are issued for this purpose. The first carries the howitzer, the second the carriage, and the third the platform and earth box, all of which is of British design, but the United States is in possession of equipment made both in this country and Great Britain. REAR VIEW OF CARRIAGE, SHOWING HOWITZER AT MAXIMUM ELEVATION. The howitzer consists of a tube, muzzle stop ring, a series of layers of steel wire, jacket, breech bushing, and breech ring. Over the exterior of the tube is wound a series of layers of steel wire extending from the breech end to the stop ring, which is shrunk over the tube at the' muzzle. Over the exterior of the tube is shrunk the jacket, which is secured longitudinally by the breech bushing. The bushing is prepared for the reception of the breechblock. The breech ring is screwed and shrunk over the jacket at the rear. (288) The Mark II differs in that it has two tubes shrunk one over the other, on which (he wire is wound. The Mark 1 howitzer is 133 inches in length, while the Mark II is 17() inches. The breech mechanism of the screw type with plastic obturator is so arranged that by partially revolving the operating lever the breech- block is unlocked and the block with the gas-check pads and disks withdrawn from the seating in the chamber. The breech mechanism can then be swung into the loading position by means of a handle on the rear face of the breechblock. The breech is closed by a parallel screw having five portions of the screw thread removed longitudi- nally, each one-tenth of the circumference. The main characteris- tics of the Vickers 9. 2-inch howitzers are indicated in the accompany- ing table, giving the important dimensions, weights, and ballistics. The Mark I breech requires two operations to open. A handle turning on the rear of the block revolves and releases the block, then BREECH MECHANISM (MARK I). it must be swung open by the handle provided on the breech. The Mark II breech can be opened by one motion of a lever on the right side of the breech, which revolves and withdraws the breech in one motion from front to back. Both types are fitted with a firing mechanism to accommodate the T-tube primer. Later models are fitted with the French percussion type of firing mechanism described with the 155-millimeter howitzer materiel 011 page 216. The recoil mechanism is of the hydropiieumatic type and is equipped with a variable recoil, which shortens the length of recoil after 15 elevation. The recoil cylinder is located above the howitzer, the former being- secured to the howitzer and moves with it, while the piston rod is secured to the cradle. The recoil is controlled by passage of oil through ports in the cylinder, which are varied by the valve located 290 near the piston on the rod. This valve is rotated by lugs which en- gage spiral grooves in the cylinder. A mixture of glycerine and oil is used in the cylinder. Later models are fitted with gravity tank on top of the recoil cylinder to replenish the oil and relieve pressure due to expansion. The end of the piston rod is extended and shaped to form a counterrecoil buffer. The recuperator is located below the howitzer; the cylinder being secured to the cradle remains stationary when the howitzer is recoil- ing; but the ram is secured to the howitzer and moves with it. The oil and air in this cylinder are separated by a floating piston. The ram on recoiling increases the liquid pressure on thi& piston ; this in turn compresses the air, which on expansion will return the howitzer to battery. An initial pressure of 475 pounds per square inch is maintained in the air chamjber to hold the piece in battery. RETAINING CHTCH BREECH MECHANISM (MARK II). To maintain this pressure a pump is attached to the carriage, which can be operated either by hand or a small gasoline engine. The cradle is a cylindrical chamber formed to house the howitzer. It is provided with trunnions and has the elevating arc secured to its lower side. Grooves cut in the cradle cylinder serve to guide the howitzer during recoil. A toothed arc on the left trunnion operates the valve turning gear through gearing. The top carriage or body is built up of steel plates. A front tran- som carries the pivot block, which fits over the pintle on the bed and on which the top carriage pivots. To the rear transom is secured a pinion which, meshes with a rack on the bed, serves to traverse the piece. Suitable platforms are hinged to the body, thus permitting access to working parts and loading platform on the rear for the per- *sonnel. On the left rear side of the body is a loading gear, which consists of a swinging arm with a winch and loading tray. 291 292 The traversing gear is actuated by a liandwheel on the left side of the carriage, motion being transmitted to a vertical rack pinion which works in the rack at the rear of the bed : thus a traverse of 30 right and left may be obtained. METHOD OF LOADING, SHOWING LOADING GEAR MECHANISM IN ACTION. The elevating gear is operated by a handwheel on the left side of the carriage, which, through a system of gearing, operates the arc beneath the cradle. RIGHT SIDE VIEW OF CARRIAGE IN BATTERY. A quick-loading gear operated by a handwheel on the right of the carriage permits the howitzer to be brought readily to the loading angle, 3 depression. The firing angle ranges from 15 elevation to 55 elevation. 293 294 295 The bed on which the top carriage pivots consists of two steel side guides of box section with transom, a pivot block, and a trav- ersing rack. The bearing of the top carriage is formed by an upper and lower roller path. At the front of the bed are suitable connec- tions for fastening a steel box which is filled with earth to help main- tain stability. Sighting is accomplished by means of a rocking-bar sight, a pano- ramic sight, or a No. 7 dial sight located on the left of the carriage. The rocking-bar sight serves to lay for elevation and carries the telescope sight or the dial sight for laying for direction. The dial sight is similar to the United States panoramic sight, which can be substituted. Ammunition employed is of the separate-loading type. High- explosive steel shell weighing 290 pounds are used, which are fitted with percussion fuses. The propelling charge is put up in cloth bags, charges being built up with four and with five increments for zone fire are provided. The charge is ignited by the T-tube friction type of primer. Weights, dimensions, and ballistics. Mark I. Mark II. Weight of howitzer without breech mechanism pounds.. Wei- lit of howit er with bree> h me< hanism do Total length of howitzer inuhes. . Rifling (uniform). Powder i haree pounds. . Weight of shell do.... Muzzle velo"ity ft. per sen. . Maximum ranre yards. . Wei< ht of mount in firing position complete with howitzer (but without dirt in earth box) pounds. . Weii h t of body and Cradle do Weirht of bed and earth box do Wei'ht of earth box empty do Woii ht of firin