If the wheels of the carriage be not on the same level the gun will shoot towards the lower wheel. A correction for this is made by a deflection-scale.
The correction for deflection due to inclination of trunnions, expressed in units of the deflection-scale, is, at any range, equal to the product of the angle of elevation and the angle of inclination of the trunnions, both expressed in degrees, into a constant multiplier. When the divisions of the deflection scale are 1/500 of the distance between the sights this multiplier is 0.1523; when the divisions are 1/1000 it is 0.3046. The rear sight must be moved towards the higher wheel.
Ammunition for 3.2-inch Gun.
The ordinary friction-primer is used for radial vents; for axial vents an attachment is made to the friction-primer of a thin brass wire about 18 inches long, looped or coiled for convenience, and having one end fastened in the loop of the friction-wire, and the other around the head of the body of the friction-primer.
The cartridge-bag is used, but experiments are now being made with metallic cases. (This proposed metallic ammunition for 3.2-inch guns comprises a projectile weighing 16½ pounds, with a suitable charge of smokeless powder to give an initial velocity of 1450 ft.-sec.)
| Charge of powder | 3¾ pounds I. K. |
| 3½ " sphero-hex. | |
| Weight of projectile filled | 13½ " |
| Bursting-charge of shell | 7 ounces |
| Bursting-charge of shrapnel | 3 " |
Shell, shrapnel, and canister are used.
Shell.—The base-percussion-fuze shell ([Fig. 42]) is made of cast iron in one piece, having a band of soft brass or copper forced into a recess on the outside, ⅝ of an inch from the base. The body and half of the head are painted black; the half of the head nearest the point is painted vermilion.
Canister.—The canister ([Fig. 43]) consists of a hollow cylinder of malleable iron, with one end closed by a cast head. The case is filled with from 222 to 226 balls, and a metal cover is inserted. Around the case are several slits, their ends overlapping to secure the thorough breaking up of the case on discharge.
