SIG SAUER P556 - Manual (Page 31)

P556 Pistol Operators Manual
31
1511582 VER 08.01.08
4.1.1. Unlocking of Bolt; Extraction & Ejection
• The gas pressure, generated by the burning powder, drives
the bullet up 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 operating rod (1) which
pushes the bolt carrier (4) to the rear.