chamber. A protrusion on the open end of the housing
h. The energy (E) supplied by this spring is equal
is threaded externally to provide a means of attaching
to the area under the spring force curve, or:
the housing to the cap. The firing pin bore houses the
initiator spring, the firing pin, the greater portion of the
initiator pin positioned within the initiator spring, and the
firing-pin-release balls. The open end of the housing
bore has a larger diameter (fig. 85) to allow the firing
i. This is four times the energy required to fire the
pin-release balls to leave the retaining groove in the
primer. A large amount of energy is lost overcoming
initiator pin, releasing the firing pin and permitting the
friction but tests made with mock-up of this firing
spring to drive the firing pin toward the primer.
mechanism showed that sufficient energy was delivered
to fire the primer. (The firing pin was propelled into
copper crusher cylinders and the indent used to
measure the energy delivered by the firing pin.)
at the other or forward end, except for a small hole
through which the end of the firing pin protrudes when it
strikes the cartridge primer. The closed portion of the
forward end acts as a stopping shoulder to limit the
forward travel of the firing pin. The external face of the
Figure 85. Firing-pin housing for initiator.
forward end contains a boss which is shaped to fit the
contour of the cartridge head. Immediately behind the
b. The firing-pin housing is not subjected to large
forward face a threaded flange is provided.
The
stresses, but several areas must be manufactured to
cartridge retainer is attached to the firing pin housing to
close tolerances. The dimensions of the closed end of
insure "zero head clearance." On the outside diameter,
the housing are critical, since they determine the firing-
the open end of the firing-pin housing is a large flange
pin protrusion and they insure that the end configuration
section which contains an O-ring groove. The O-ring
of the housing supports the cartridge when it fires.
prevents propellant gas from escaping from the
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