Just before the grenade is thrown, the hook is engaged in the ring of the roughened wire of the friction primer placed inside the fuse plug which closes the cast iron ball. When the grenade is thrown, the ring with the primer wire, held back by the hook of the bracelet, is wrenched off by a sudden movement of withdrawal from the wrist and the fuse is fired. The explosion takes place four or five seconds later. This grenade is supplied to the fighting zone ready for use. It is quite complicated. It can be thrown about 25 meters. The German grenade is composite; it can be thrown by hand or fired from a rifle. As a hand missile, it is used at short distances, 15 to 20 meters. It is composed of a copper rod to the extremity of which is fixed a cast iron cylinder, grooved to facilitate its breaking into small pieces at the moment of explosion. The explosive is placed inside this cylinder. A copper tube, also containing some explosive, is placed in the interior. It is surmounted by a complicated system for closing the grenade and for automatic ignition by percussion, which results in at least 50 per cent of misfires. [Illustration: PLATE 41b.—British hand grenade No. 1. _a._ Removable cap. _b._ Detonator holder. _c._ Detonator. _d._ Explosive charge. _e._ Wood block. _f._ Handle. _g._ Safety pin. _h._ Firing pin. _i._ Cast iron ring. _j._ Streamer. ] [Illustration: PLATE 41c.—The latest type British hand grenade. _a._ Percussion cap. _b._ Firing pin. _c._ Safety pin. When in place prevents firing pin from striking primer. It is removed just before throwing the grenade. _d._ Primer. _e._ Chamber filled with high explosive. _f._ Cast iron shell, serrated. _g._ Wooden handle. _h._ Streamers, to keep the grenade head-on.] Used with the rifle, this grenade has a maximum range of 400 meters. At the extremity opposite the grenade, the copper rod ends in a copper stem about 3 centimeters in length, movable about the axis of the rod. This stem is covered with a copper sleeve of slight thickness, which is attached to it only at the extremity fastened to the rod. The diameter of the exterior of the sleeve must be such that it can be pushed into the gun barrel without pressure. To fire the grenade, a blank cartridge is placed in the chamber of the rifle; the quantity of powder left in the cartridge is regulated according to the distance at which the missile is to be thrown. At the moment of firing, the explosive gases penetrate between the sleeve and the stem and jam the sleeve against the grooves of the barrel. The sleeve and the stem, which is attached to it, take a movement of rotation in the grooves of the barrel, which insures the direction of the missile and the maximum efficiency of the explosive gases of the cartridge.