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Figure 4: The locking step in the cycle of operations.
cartridge from internal pressure forces weight of the bolt/slide and the strength
the surfaces of the bolt/breech/slide of the recoil/return spring, combined
against the surfaces of the barrel/receiver. with the friction between the cartridge
The chamber will stay locked until it case and chamber, resist the back thrust
is safe to unlock. Mechanical locking of the discharging cartridge. Blowback
chambers are typically reserved for most actions are typically reserved for rimfire
pistols, rifles, and shotguns. and low power pistol cartridges.
Revolvers lock mechanically, but much • Cocking – The cocking step in the cycle
differently than other firearms. As the of operations sets the fire control group
cylinder spins and comes into alignment components to the “cocked” or ready-to-
with the barrel, a part called the cylinder fire position. This can happen in various
stop will engage a corresponding notch ways depending on the type of fire con-
in the cylinder. When the cylinder stop trol group employed. The firearm may
engages the notch, it will lock the cylin- use either a hammer and firing pin, or
der in place, in alignment with the barrel. striker. The mechanism may be cocked
The locking step typically happens in either manually or automatically depend-
conjunction with the cocking step. ing on the action.
Blowback actions rely on inertia and The hammer of the striker is under
friction to lock the breech until pressure constant load from its respective spring.
has dropped enough to safely open. The When the action cycles (manually or
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