The hydraulic recoil consists of two cylinders placed laterally and at the height of the axis of the piece.
The axle has the peculiarity that in its centre there is a wide opening in which are placed the cradle and the gun. It is provided with two screw trunnions, around which the pivoting necessary for lateral aiming is effected. This arrangement of the gun with respect to the axle has the effect of greatly diminishing the shocks that firing tends to produce.
Elevation and depression are accomplished by rotating the axle in the wheels of the carriage. This is done by means of a crank which, through an endless screw and pinion, controls a toothed sector attached to the sleeve.
Pointing in direction is done by means of a lever known as a tail piece. Mounted upon the axle there are two small sights, forming a line of aim, that permit of bringing the carriage back in the direction of the target as soon as a shot has been fired. All that the gunner has to do is to give the piece a slight displacement laterally with respect to the carriage by means of a hand-wheel, which turns the gun 2° to one side or the other.
The line of aim is found by a back and front sight arranged upon the right side of the sleeve in which the gun is mounted. The back side permits of aiming while the gun is being loaded. It carries a small oscillating level that indicates the elevation of the gun during rapid firing.
The weight of the carriage, without wheels, is 1,146 lbs. and with wheels, 1,477 lbs.
The ammunition consists of cartridges containing charge and projectile and having a total weight of 19 lbs. The powder employed is of the smokeless kind, designated by the letters B.N. The weight of the charge is 1-¾ lbs. The projectiles are of three kinds—ordinary shells, shrapnel shells, and case shot. The weight of each is the same, say 14-¼ lbs. The shrapnel shells contain 234 balls, weighing 155.8 grains each, and an explosive charge of 3.13 ozs.
As the gun can be pointed at a maximum angle of 20°, and the initial velocity is 1,837 feet, the projectiles can be fired to a distance of 26,248 feet.
The crew necessary to serve the gun consists of six men—a gunner, a man to manœuvre the breech-piece, a man to manœuvre the pointing lever, two men to pass the ammunition, and a man to regulate the fuse. The rapidity of firing can easily be raised to ten shots a minute.
The accuracy of the gun is most remarkable. Upon the occasion of the trials made when the guns were received, the following firing was done: a regulating shot, a first volley of six shots in forty-two seconds, and a second volley of six shots in forty-six seconds.