Description: The cast iron body is cylindrical and has 50 serrated segments. A filling plug screws into the upper end of the body, and a brass fuze screws through this plug. The base of the grenade is threaded, but not entirely through to the charge. Into these threads fits the propellant container.

The fuze consists of a brass inertia pellet with a steel firing pin separated from the primer by a creep spring. The inertia weight is held in the fuze by a light brass cap which is crimped into a cannelure in the fuze body so as to prevent the firing pin from reaching the primer. The firing pin is threaded into the inertia weight. In addition, a double brass safety pin fits through the fuze, preventing the firing pin from reaching the percussion cap.

The delay pellet screws into the base of the fuze and contains a small quantity of granu-lar black powder and a pellet of black powder. A hole drilled in the side of the fuze con-tains a fusible plug which melts when the black powder burns, allowing the escape of the gases formed on combustion of the delay train. The tetryl detonator is contained in a brass tube extending from the base of the fuze to the bottom of the bursting charge.

The steel propellant container is screwed into the base of the body. A perforated plug screws into the base of this container and in a cavity in this is a percussion cap. Two flash holes lead to a small quantity of black powder. Inside the propellant container pro-per is a copper cup containing flakes of nitrocellulose propellant powder.

When this grenade is used as a rifle grenade, a finned tail stabilizer is screwed into the base of the grenade instead of the propellant container.

Operation: The firing pin must first be threaded down into the inertia weight. The safety pin must then be withdrawn. If the grenade is to be thrown by hand, it is necessary to strike the inertia weight on some hard object to drive the firing pin into the primer to ig-nite the delay train.

If the grenade is to be fired from the grenade discharger, the grenade with propellant container is dropped base first into the discharger. When the trigger mechanism of the discharger is operated, its firing pin strikes the percussion cap, igniting the propelling charge which propels the grenade. Force of setback causes the firing pin in the grenade fuze to compress the creep spring and hit the primer to ignite the delay train.

To fire the grenade from a rifle, the stabilizer is placed over the launcher and the rifle is fired using the special cartridge. The shock of discharge forces the striker into the primer igniting the delay.

Figure 169 – Type 91 Hand, Mortar, or Rifle Grenade.