The =Gun= is known officially as the _3-inch Field Gun, Model 1905_. It is a built-up construction of nickel-steel and consists of a tube with a rifled bore, 3 inches in diameter, upon which are shrunk the jacket, locking hoop and front clip hoop. The jacket reinforces the rear half of the tube. The locking hoop serves to secure the jacket from any longitudinal movement to the rear. On the under side of the gun, extending the entire length of the jacket, locking hoop, and front clip, are formed two recoil guides or clips which fit over and secure the gun to the guide rails of the cradle. When the gun is fired, it slides along the guide rails. The dust guard covers the part of the guide rails between the locking hoop and the front clip. The rifling of the bore is right-hand twist and starts with 0 turns at the breech increasing to 1 turn in 25 calibers at 10 inches from the muzzle, then uniform to the muzzle. Weights and Dimensions. Weight of gun 788 lbs. Calibre 3 inches Length about 7 feet Number of lands and grooves 24 Muzzle velocity 1700 ft. sec. Maximum pressure per sq. in. 33,000 lbs. Limit of depression (90 mils.) 5 degrees Maximum elevation (265 mils.) 15 degrees Maximum range, trail sunk, about 8,500 yds. (5 M) Range at 15° elevation (265 mils) 6,000 yds. (3½ M) [Illustration: _3 Inch Field Gun, Models of 1904 & 1905._ _Breech Mechanism Assembled._] Nomenclature of parts of Gun:— Jacket. Locking hoop. Tube. Bore. Rifling. Lands. Grooves Breech recess. Front clip. Muzzle. Dust guard. Recoil guides or clips. Chamber. Recoil lug. Line sight (front and rear). Handy oilers. THE BREECH MECHANISM. The =breechblock= is of the interrupted-screw type, and is provided with four threaded and four slotted sectors. The front end of the axial recess in the block is closed by a bushing. Four ventholes lead from a cavity in the bushing and permit the escape of gas to the rear in case of a ruptured primer. On the rear face of the breechblock are cut gear teeth, in which the gear teeth of the operating lever bevelgear mesh. The breechblock is concentrically mounted on a hub on the block carrier, in which the firing-lock case is fitted. Its position in the breech of the gun with reference to the axis of the bore is eccentric.