3 unlocking and recoil of bolt – SIG SAUER SIG556 User Manual
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illUS. 58) Bolt Carrier
reCoil BeginS
4.1.3 Unlocking and Recoil of Bolt
The gas pressure, generated by the burning powder, drives the bullet through the barrel (13). As soon as the projectile
passes the gas port (15), propellant gas flows through the adjustable gas valve (14). The gas pressure acts on the gas
piston (1) which pushes the bolt carrier (4) to the rear.
During the rearward motion of the bolt carrier (4) the bolt head (5) is rotated by the control cam (3) so that the locking
lugs (8) are disengaged. The bolt is now unlocked.
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