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Figure 33: Short stroke piston system.
There is a huge array of short stroke During discharge, the high pressure gas
piston-operated firearms, with many very that is tapped by the gas port is directed
notable military service weapons. The through a gas block and into a gas tube
FN SCAR series of firearms and many that leads to the carrier. The gas drives
AR-15 variants utilize a short stroke pis- the carrier rearward, which unlocks the
ton system, which only uses a piston to bolt/breechblock and completes the cycle
drive the action. The VZ 52 rifle and the of operations. Any residual gas is vented
SKS rely on short stroke actions that use into and out of the receiver.
a piston and an operating rod.
Of the three gas-operated actions, the
• Direct Impingement – The direct direct impingement system tends to be
impingement system differs from both the most finicky. The whole system must
of the piston systems in the fact that be “tuned” to assure proper function. This
there is no piston involved. With a means that the diameter of the gas port
direct impingement system, the carrier and its location from the chamber are
itself is moved directly by the gasses critical to assuring that there is enough
from the cartridge. The movement of volume of the correct pressure gas. The
the carrier will facilitate the breech highest pressures are generated near the
locking and unlocking. chamber, so placing a specifically sized gas
port farther down the barrel will tap gases
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