Firing pin

A review of the vast amt of work performed in the field of percussion primers reveals what is essentially an empirical approach to the development of both primer designs and priming mixts. It is recognized that a percussion primer must perform two vital functions (1) it must fire , ignite , or otherwise function when provided with the proper mechanical stimulus — a firing pin (with optimum contour to its striking end) and (2) it must perform its other function by which the flame , fire , or output will ignite the proplnt properly so as to provide the projectile with the specified velocity and within... 

In order to fire reliably in a gun or other weapon device, a percussion primer must possess impact sensitivity which is in consonance with the mechanical energy delivered by the firing pin. In all cases, a factor of safety is built into the system in such a manner that the firing pin energy usually exceeds the max energy requirement of the primer by approx 20%... 

When a percussion primer is used to drive a firing pin to cause a series of events to occur, an important aspect of primer output is the moment-... 

In mechanical fuses, where percussion primers are required, it seems fairly obvious that space requirements impose limits on the size of spring mechanisms or other physical modes of causing firing pins to move. The result is that, for fuses and other applications of this type, it becomes necessary to use primers of greatly increased sensitivity (Refs 6 8). This condition is illustrated with the M29A1 primer which is required to fire with an applied energy of 16 inch-ounces. This increased sensitivity is achieved by the use of thinner primer cup metal of softer alloy. Sensitivity can be further enhanced by the use of more sensitive priming mixt (Refs 2,6 20)... 

Since stab detonators contain no restraining anvil as do percussion primers, the resistance to penetration of the firing pin becomes quite im-. portant. This is the role of compression or density of the mixt. With higher density, the kinetic energy of the firing pin is dissipated over... 

Since the resistance of solids to deformation does not change very much with moderate changes of deformation rate, the power dissipation by the displacement of compressed priming mixt by a firing pin is nearly proportionate to its velocity (Ref 19)... 

When designing a stab detonator, the engineer will select the firing pin so that the entire initiation mechanism is under control. This permits close coordination with other systems designers involved in the weapon development, and thus insures that the stab detonator will receive the proper stimulus... 

What has been described so far constitutes only one half of the friction primer, ie, the main charge, contained in a cylindrical cup. Centrally located in the K chlorate mixt was a loop of braided wire, coated with red P (90%) and dried shellac (10%). Any mixt of red P with K. chlorate was, and still is, very sensitive, hazardous, and unpredictable. There is ample reason to understand why friction primers were abandoned and replaced with spring-actuated firing pins to fire percussion primers and carry the sequence thru a suitable expl train... 

To use this device, firmly lash the unloaded rifle to a fixed object such as a stake or tree. See Figure 20. Tie a long pull cord or trip wire to the trigger and test the empty weapon once or twice to see that the trigger moves freely when pulled and that the firing pin snaps forward. 

Detonators are used to detonate high explosives. Stab detonators are initiated by sharp firing pins and are used in explosive trains of different types of fuses. Flash detonators are initiated by flames produced by safety fuses, primers, or delay elements. A special type of flash detonator ignited by the flame of a safety fuse is called a blasting cap. Detonators are primarily composed of three types of explosives including sinoxid mixtures, lead azide-based mixtures, and mercury fulminate-based mixtures. 

Given the unreliability of the stab-initiated tests, a second round of testing was performed using a hot nichrome wire to initiate the detonators in place of the NOL-130 stab mix and firing pin. This test was successful and all nine detonators functioned, showing that DBX-1 is more susceptible to this method of initiation. Figure 8 shows the electrical ignition setup. 

Primer A term for the device used to ignite smokeless powder in small arms ammunition. An impact-sensitive composition is used. When struck by a metal firing pin, a primer emits a burst of flame capable of igniting the propellant charge. Several typical primer mixtures are given in Table 6.2. 

In the pull operation, a direct pull of 6 to 10 pounds on the trip wire causes the release pin and firing pin to be pulled outward until the jaw end of the firing pin passes beyond the constricted opening of the body. In this position, the jaws spread, thereby releasing the firing pin which, driven by its spring, fires the primer... 

These primers can be used not only in small arms but also in some pyrotechnic devices and fuzes. All simple primers are small in size, 0.21 to 0.31 inch in diam and 0.12 to 0.23 inches long for rifle ammunition and slightly Smaller for carbines. They contain only one small charge of primary expl or a mixture which must have sufficient sensitivity to be initiated either by the crushing or stab action of a firing pin... 

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