Shot and shell used with muzzle-loading rifles are now provided with a copper disc attached to the base, called a gas-check. This disc is slightly convex to the rear to enable it to spread and stop the windage on firing. It is attached to the projectile by means of a screw-plug and nut. On firing, it is expanded into the rifling and completely stops the windage. It gains a grip on the base of the shell by means of an undercut rim, whilst radial scores on the base prevent it from gaining an independent rotary motion, and enable it to assist in rotating the projectile. [Illustration: Palliser Shot.] [Illustration: Papier-maché Wad.] [Illustration: Brass Gas-Check for Projectiles.] All muzzle-loading projectiles are provided with studs for rotation. They are of gun-metal, swedged into countersunk holes, in two rows. The loading side of all grooves is cut back so as to double the width of the groove at the muzzle, in order to facilitate the insertion of the projectile. Papier-maché wads are used in front of the heavier projectiles to keep them from slipping forward out of place. These wads are very slightly less than the calibre of the gun, and about an inch in thickness. A hole is bored through the centre, large enough to leave a clear space for the fuse. A short papier-maché tube projects from the forward side of the wad, which serves to attach it to the rammer when loading, and hold it vertical while the charge is going home. Shell-charges for Palliser projectiles are introduced in serge bags to prevent premature explosions. FUSES. Both time and percussion fuses are used in the navy. The time-fuses are the Boxer and the Armstrong; the latter used only with breech-loading segment shell. The percussion fuse is the Pettman. The Boxer time-fuse has a beech-wood body and is conical in shape. The fuse composition is a vertical column in a centre channel which is not bored entirely through the bottom, a base being left to receive the set-back of the column on firing. Two side channels are bored from the bottom nearly to the top, and are filled with mealed powder. Holes are bored from the outside into these channels one tenth of an inch apart, and the composition burns at the rate of one inch in five seconds, so that each hole represents a half-second. The head of the fuse is closed by a safety-cap, which is removed before loading. The time of burning is set by boring through the desired hole into the composition. The bottom hole is always bored through. [Illustration: Boxer Time-Fuse.] [Illustration: Armstrong Time-Fuse.] [Illustration: Armstrong Percussion Fuse.]