Pressure Firing Device M1A1

General: This is a mechanical device designed to fire explosive charges by means of pressure. A pressure of 20 pounds or more applied to the trigger pin will actuate the de-vice. Various extensions, for attachment to the pressure head, are issued with the de-vice, in order that it may be adapted to varying circumstances.

Description: Principal parts are the body, trigger pin and pressure head, striker spind-le, standard nipple base, safety clip, and safety pin. The projection of the trigger pin which extends down into the body has two holes of varying diameter with an inter-con-necting slot. The hole toward the bottom of the trigger pin is the smaller. The striker spindle has a circumferential groove around the part that extends through the trigger pin. When the device is set, the trigger pin is held up either by a clip or just by its spring, and the grooved part of the striker sprindle is engaged in the smaller hole on the trigger pin. In this position the striker spindle is locked and cannot fire.

Operation: When the device is armed, the striker spindle is engaged in the lower (smaller) hole in the trigger pin, and the pin in turn is held up by the trigger-pin spring. If a pressure of 20 pounds or more is applied to the pressure head, the trigger pin is forced inward and the larger hole in the projection of the pin is moved into line with the striker spindle. The head of the striker spindle can pass through this hole, and the striker is free to be forced against the percussion cap by the compressed striker spring.

Remarks: With the trigger spring removed, a pressure of only five pounds will actuate the device. The extension rod or the three-pronged extension can be threaded into the pressure head.

Figure 247. Pressure Firing Device M1A1