Pull Firing Device M1

General: It is a mechanical device designed for firing charges by a trip wire. A direct pull of thrre to five pounds applied to the ring actuates the device. A spring-driven firing pin sets off the percussion cap, which, in turn, sets off the non-electric cap crimped to the base. This cap detonates the explosive charge. The new model has two safety pins; the old model did not have the positive safety pin.

Description: The principal parts are the body, release pin, washer, firing pin, and standard nipple base. The split head of the firing pin is forced against pressure of the striker spring through a small opening formed by the shoulders inside the body. The re-lease pin enters into and expands the split head of the firing pin against these shoulders, thus preventing its return. The release pin is held in position by the loading spring. Holes in the main head and the release pin permit insertion of a safety pin to prevent acciden-tal movement of the release pin. The main head or upper body is threaded onto the lower body. A short piece of wire is attached at the side to be used in anchoring the device.

The new model differs in that the positive safety pin was added just below the stri-ker; water-proofing material was added around the nipple of the base; and an anchor cord is used in place of the wire. The head of the body differs slightly in construction, and the joint is soldered to prevent disassembly.

Operation: When the device is set with the blasting cap crimped to the base and in-serted in an explosive charge, the top safety pin is removed. After checking the device, the positive safety pin in the lower part of the body is pulled free (new model), and the device is in an armed condition. A pull of three to five pounds on the release pin is suffi-cient to overcome the resistance of the loading spring and cause the tapered end of the release pin to be withdrawn from within the split head of the firing pin. The split head, no longer being forced against the internal shoulders of the body, slips through under the in-fluence of the striker spring, which drives the striker down on the percussion cap.

Figure 245. Pull Firing Device M1