a. General. A firing device is designed to initiate a train of fire or detonation of demolition charges, boobytraps or mines, principally by initiation of a nonelectric blasting cap or a mine activator. It is a separate item of issue and is packed in its own box. Firing devices are of two general types: tubular and box. The coupling base, fitted to all types, has a standard thread and nipple and always contains a percussion cap primer. The coupling base may be removable or permanently attached (as in the pull-friction and delay types), depending on firing device model. Firing devices may be used interchangeably, as indicated by the task to be accomplished. They may be used with demolition charges and heavy antitank mines (if fitted to activators), light antitank mines or destructors. When a firing device is used with a service activator or a practice activator (see TM 9-1345-203-12&P), a blasting cap cannot be used. When used with light antitank service mines or with demolition charges or a universal destructor, a firing device requires a crimped-on blasting cap.
(1) Tubular type. Tubular firing devices, consisting generally of head, case, coupling base and percussion cap primer, are arranged for actuation by pressure, pull, release of pull or chemical action.
(a) The delay-type demolition firing device (fig. 8-18) is a chemical device used with delayaction mines and demolition blocks. It contains a glass capsule filled with corrosive liquid, located in a thin-walled portion of the case. An identification and safety strip, color-coded to indicate the delay time of the device, is visible through an inspection hole in the coupling base. The nominal delay time (at +75°F.) is color-coded as follows: 9 minutes, 'black; 15 minutes, red; 1 hour, white; 21/2 hours, green; 51/2 hours, yellow; and 11^/2 hours, blue. The nominal delay time is subject to temperature correction in accordance with a table furnished with the firing device.
(b) The pressure-type demolition firing device (fig. 8-19) is used in setting up boobytraps. On removal of the safety pin between the firing pin and primer, a pressure of about 20 pounds on
the pressure cap acts to release the spring-loaded firing pin that fires the primer.
(c) The pull-friction type, which contains a friction-initiated primer, is actuated by a pull wire. This type is used in setting up boobytraps. The body is plastic and the base is nonremovable. A coated wire, to which a spring and pull ring are attached, passes through the body, and through the friction compound into a nipple on the base. A direct pull of 3 to 11 pounds on the trip wire (pull wire) stretches the spring. This draws the coated wire through the friction compound. As a result, the friction compound ignites.
(d) The pull-release type (fig. 820) is a mechanical device actuated by either an increase (pull) or a decrease (release) of tension in a taut trip wire. This type is used with antipersonnel mines or in setting up boobytraps. Either a direct pull of 6 to 10 pounds on the trip wire or a release of tension (such as cutting or detaching the trip wire) releases the spring-loaded firing pin that fires the primer.
(e) The pull type is a mechanical device actuated by a pull on a trip wire (fig. 8-21). This type is used with some antipersonnel mines or for boobytrapping antitank mines. A direct pull of 3
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