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impacts the primer cup, the priming As the bullet begins to travel through the
compound is crushed between the primer bore, the rifling will begin to impart spin
cup and the anvil. When the priming onto it. The pressure will continue to
compound is ignited, burning embers build as the remaining propellant burns
and incandescent particles travel from until all of the propellant has ignited.
the primer through the flash hole and The pressure will force the bullet from
onto the propellant. Note that there is the bore and out of the muzzle. Any re-
no flash hole with rimfire cartridges; the sidual propellant or pressure in the bore
embers travel straight to the propellant will follow the bullet out of the muzzle.
(Figure 6b).
As pressure drops inside the bore and
The embers from the primer ignite the chamber, the case will begin to contract
propellant in the body of the case. The and open its seal against the chamber.
propellant begins to burn (deflagrate) When the pressure inside of the bore
and produce rapidly expanding hot gas. and chamber equalizes with atmospheric
The expanding gas begins creating pres- conditions, the breech becomes safe to
sure, which begins acting against the unlock. The case is also ready to be ex-
case. The soft brass cartridge case begins tracted from the chamber. At this point,
to expand and seal (obturate) the cham- depending on type, the action can/will
ber from the breech. Once the case has complete the next step of the cycle.
fully formed to the chamber walls and
With revolvers, much of the firing se-
has no more room to expand, the gas
quence is the same up to the point where
begins to act against the bullet. The pres-
the bullet is pushed from the cartridge
sure will begin to force the bullet from
case. Once the bullet leaves the case, it
the crimp in the mouth of the case into
is forced through the forward portion of
the bore of the barrel (Figure 6c).
the cylinder. The projectile will then have
The bullet is forced from the cartridge to pass through the cylinder gap. The
case into the throat of the chamber and cylinder gap is an open space between
onto the leade (lead). The leade will the cylinder and the barrel that ranges
guide the bullet into the bore and rifling. in size from .003” to .013”, depending
Figure 6d: The bullet is forced through the bore and out of the muzzle.
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