SIG SAUER SIGM400 Rifle - Manual (Page 49)

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4.1. Firing
Rotate the fire control selector from the “SAFE” position to the “SEMI” position.
Pressing the trigger rearward releases the hammer causing it to strike the firing pin, impacting the cartridge primer.
CAUTION: THE SIG M400 IS A SEMI-AUTOMATIC RIFLE AND WILL AUTOMATICALLY RELOAD THE NEXT CARTRIDGE IN THE
MAGAZINE AFTER THE CHAMBERED CARTRIDGE IS FIRED FOLLOWING ONE PRESS OF THE TRIGGER. THE RIFLE WILL NOW
BE READY TO FIRE AGAIN ONCE THE TRIGGER IS RELEASED.
4.1.1. Unlocking of Bolt; Extraction & Ejection
1. The gas pressure generated by the burning powder in the cartridge, propels the bullet through the bore of the barrel.
2. When the bullet passes the gas port in the barrel a portion of the gas flows up into the gas block and into the gas tube.
3. The gas travels through the gas tube and drives the bolt carrier rearward.
4. As the bolt carrier moves rearward the cam pin allows the bolt to rotate to the right and unlock from the barrel
extension.
5. As the bolt carrier continues rearward movement the extractor, gripping the right side of the expended cartridge case
pulls the case from the chamber.
6. Once the expended case clears the chamber, the ejector located on the left side of the bolt face pushes the case out
the ejection port located on the right side of the upper receiver.
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