As soon as the block is locked, pulling the sear fires the gun. FIXED AMMUNITION. Smokeless powder will be used, about 1¾ lbs. forming the charge. The shell, cast iron, weighs 16 lbs. and also contains a bursting-charge of 8 oz. of powder. The shrapnel will be similar to the Frankford Arsenal shrapnel now manufactured, but longer and heavier (16 lbs. 10 oz.), and will break into about 240 pieces (balls and fragments). The metallic case, brass or aluminum, has the projectile inserted in it to the distance of 1.75 inches, the base of the projectile being separated from the powder-charge by a felt wad. The total length of a round is 18.33 inches. Experiments with charges of Troisdorf powder from 1 lb. 8 oz. to 2 lbs. 1 oz. have given with the 3.2-inch gun velocities from 1765 to 2032 ft.-sec. =Supplying Ammunition.=--It is proposed to have boxes that can be readily opened and closed containing a certain number of rounds, about ten for 3.2-inch gun, carried by the supply-train. When a battery requires ammunition, the boxes will be taken from the ammunition-wagon, opened and the chests filled. The empty metallic cases with the battery are then placed in the boxes, which are securely closed, loaded on the ammunition-wagon and returned to the depot by the officer in charge; and are from there returned by the ordnance officer to the Frankford Arsenal to be again filled and prepared for service. The cost of supplying ammunition by this method will be less than it is now. CHAPTER II. 3.2-inch Guns. Sights. Ammunition. Fuzes. Range Table. 3.2-INCH B. L. RIFLE, MODEL 1885 (MODIFIED). (Fig. 38.) Material steel Total length 7.56 feet Calibre 3.2 inches Weight 829 pounds Grooves 24 Twist of rifling, uniform 1 turn in 30 calibres Axis of trunnions above ground 3.56 feet Powder-chamber ellipsoidal Vent radial Preponderance 50 pounds Muzzle velocity 1685 ft.-sec. Maximum range for shrapnel[4] 6613 yards This gun consists of a tube (_a_), jacket (_b_), trunnion-ring (_c_), sleeve (_d_), key-ring (_e_), locking-ring (_f_), base-ring (_g_), and breech mechanism, De Bange obturator, vent-bushing of copper. 3.2-INCH B. L. RIFLE, MODEL '90. (Fig. 39.)