Page 125 - FAT 105 4.17 MOODLE

The hammer-fired system is so named because The firing pin is housed separately from the
its action is similar to a hammer hammering a rest of the fire control group and may be one
nail, with the only exception being the firing of two types: floating or sprung. Floating firing
pin. A part called the hammer is used to strike pins move freely within their respective hous-
a part called the firing pin, which in turn strikes ing. The weight of the floating pin is critical in
the primer. And there are two ways the system semi-automatic and automatic firearms because
can operate. the momentum of the pin will carry the pin for-
ward during the feeding and locking stages of
First, when the trigger is pressed, the trigger
the cycle of operations. You will notice that with
itself will directly act upon the hammer, releas-
some floating firing pin designs there are small
ing it and causing ignition (like with an AR-15
indentations on the primers of loaded rounds
fire control group). Second, when the trigger is
that were not fired. The floating firing pin de-
pressed, the trigger will act upon a transfer bar,
sign has the potential to cause a malfunction
or sear, which acts upon the hammer. The 1911
called a slam fire. A slam fire occurs when the
uses a design similar to this.
firing pin becomes wedged in the forward posi-
Typically, the fire control group lives in the
tion and the bolt/slide closes on a live round.
frame/receiver of the firearm and the firing pin
The sprung firing pin was designed to prevent
lives in the bolt/breechblock/slide. Both the
this issue. A light power spring is used to hold
hammer and the trigger pivot on pins in the
the firing pin rearward. When the hammer
frame/receiver. When the trigger releases the
strikes the firing pin, the energy delivered over-
hammer, the hammer will pivot around its pin
powers the firing pin spring, driving the firing
under spring force. The weight and speed of the
pin forward and causing ignition. Once the ac-
hammer is critical to proper ignition without
tion cycles, the spring will force the firing pin
damage to the primer.
rearward once more.

Figure 3: Hidden hammer hammer-fired system.

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