Combination Firing Device Mk 1 Mods 0 and 1

General: This a mechanical device for firing by means of pressure or by release of pressure. The method of activation is dependent on the manner in which the device is set.

Description: The principle parts are the body, trigger pin, firing pin, base, trigger eye, and knurled nut. The projection of the trigger pin extending down into the body has two slots with an inter-connecting hole which is large enough to permits the firing pin to pass through. When the device is set, the groove of the firing pin is engaged in either the up-per or the lower slot of the trigger pin. The trigger eye threads into the lower end of the trigger pin and can be used with a trip wire for functioning by either pull or tension-re-lease, dependent upon the method in which the device is set. The knurled nut is the safety device to prevent premature fring.

Operation: The device can be set to function either by pressure and pull or by pres-sure release and tension release. The method of actuation is dependent on whether the trigger pin is in "out" or "depressed" position. The trigger pin is moved until the hole is moved in line with the firing pin and release it. The cocked firing pin is driven on to the percussion cap by the firing-pin spring.

Mk 1 Mod 0: Installation and operation of the Firing Device Mk 1 Mod 0 is similar in all respects to the Firing Device Mk1 Mod 0. Construction differences are as follwos: The barrel, head, and plate are die-cast in one piece. A cotter safety pin passes through the barrel between the firing pin and the primer. (This cotter pin is removed after the safety nut has been threaded off. If the pin does not come out easily, the firing pin may have been released.) The trigger eye has been replaced by a removable ratchet reel, so that more accurate adjustment of the trip or tension wire is possible. A three-pronged trigger button is shipped with the device, which may be substituted for the regular trigger but-ton. Actuating pressures the Firing Device Mk 1 Mod 1 range from 11 to 16 pounds.

Figure 250. Combination Firing Device Mk 1 Type