The Whitworth groove is of a peculiar nature, being almost a perfect hexagon, and having an extremely sharp twist of from one turn in 2 feet in the 2-pdr. to one turn in 13 feet in the 9-inch.
The projectiles are cut to fit the grooves, the armor-punching ones being of compressed steel.
Whitworth Projectiles.
THE VAVASSEUR CONSTRUCTION.
Vavasseur ordnance is used considerably in China, and has found some use in other quarters of the world. The gun belongs to the steel type. It consists of a mild-steel oil-tempered tube, reinforced by steel hoops, the hoops being narrow and numerous and shrunk on. The trunnion-hoop is of wrought iron. The gun has, properly speaking, ribs instead of grooves, the grooves being cut in the projectiles. The twist is a constant one.
Vavasseur Gun and Carriage.
The gun-carriage possesses a peculiar recoil arrangement, consisting of a heavy screw-shaft traversing the middle of the slide and carrying at its forward end a wrought-iron friction-wheel with a metal strap worked by a lever, by which any desired amount of friction may be applied. Attached to the carriage is a sleeve or clutch grasping the screw-shaft. When the gun recoils, the motion of the sleeve along the shaft causes the latter to revolve, the friction being regulated by the friction-band. For running in and out a large cog-wheel is fixed to the inside of each carriage-bracket, the cogs taking in racks along the sides of the slide. In starting the gun out, the motion of starting slacks the friction-band on the screw-shaft, allowing the gun to run freely; for controlling the motion in a seaway, a small friction-brake on the rear of the slide is used. The carriage is mounted on eccentric rollers, and the movement of throwing them out of or into action ungears or gears the running-out cranks outside of the brackets, so that in recoiling the cranks are not thrown around. The chamber of the Vavasseur gun, as originally constructed, is smaller than the bore, being in this a reversal of the present accepted true principle, and limiting the guns to small charges and low velocities.