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moment of discharge, the action cycles cartridges, the bolt/slide would have to
very quickly. With semi-automatic ac- be extremely heavy, which would make
tions, this means the operator experi- the recoil feel like a kick from a mule,
ences less “felt” recoil. This means the and the action/recoil spring would have
actual amount of recoil delivered may be to be so powerful that manually charging
greater, but because the recoil impulse is the action would be impractical.
so brief, the operator does not feel the
Certain ammunition can also create vari-
force as greatly. This also means that a
ous problems for the straight blowback
high rate of fire can be achieved with
action. Because there are various types of
enough skill. With automatic actions, a
ammunition for single rimfire caliber, it
fast cycling action means a high rate of
would be hard to design an action (that
rounds-per-minute (rpm). While most
relies on the ammunition’s energy) to
locking breech automatic firearms have a
run with every type. Most manufacturers
cyclic rate of around 600 – 900 rpm, au-
tune their firearms to run with a specific
tomatic blowback firearms cycle around
type and even brand of ammunition, as-
1,100 – 1,200 rpm.
suring the most reliable function. Using
Major drawbacks to the straight blow- ammunition that is not recommended
back design include a limited selection can lead to various issues. Using ammu-
of chamberings, ammunition selection, nition that is below the manufacturer’s
and feeding issues. Because the chamber recommended power level can lead to
does not lock, the action can only handle failures to extract and eject, failure to
rimfire cartridges. For higher power cock the hammer/striker, and failure to
feed and lock the chamber. Using am-
munition that is more powerful than the
manufacturer’s recommendations can
cause the bolt/slide to batter the frame
because it was not designed to handle so
much power. It can also cause failures to
extract when the extractor slips over the
case rim because the case is not ready to
contract and the case becomes stuck in
the chamber. As well, it can cause a fail-
ure to feed when the bolt/slide outruns
the feeding device and the bolt/slide runs
over top of the round or only catches the
edge of the round.
The components of the cartridge itself
may also cause further malfunctions to
the blowback action. Rimfire cartridges
typically use solid lead projectiles and
propellant that burns fairly dirty. Lead
will build up in the throat of the cham-
ber and bore and carbon and unburned
propellant will build up in the firearm’s
Figure 3a: Straight blowback pistol.
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