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Figure 34a (top) & Figure 34b:
Direct impingement system.
that are a lower pressure. This assures the distance from gas port to muzzle, the
action will not face any unneeded wear longer the system stays pressurized, as-
from over-pressurization. The system also suring there is enough gas to properly
relies on the length of the barrel ahead of cycle the action. Dwell is not really a
the gas port for “dwell time.” concern for the two piston-driven ac-
tion types because of the operation of
Dwell time is the length of time the gas
the piston and the often oversized gas
system stays pressurized. Dwell begins
port. Both piston systems tend to be
when the bullet passes the gas port and
overly pressurized at the gas port, which
the system begins to pressurize and ends
typically is bled off once the piston has
when the bullet exits the muzzle and
moved a short distance.
the system is “uncorked.” The longer the
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