Post Barrel Plenum Operated Gas Cycling System for Automatic Firearms

A gas buffer plenum positioned at the end of a firearm barrel to collect, store and direct high pressure gas through a gas tube back to a receiver of the firearm to cycle a bolt of the firearm after the bullet has exited the barrel, the gas buffer plenum comprising:

• (a) a plenum enclosure having a barrel oriented end and a target oriented end;
• (b) a barrel-side wall on the barrel oriented end of the plenum enclosure, the barrel-side wall comprising:
• (i) a center axis barrel collar attachable to the end of the barrel of the firearm;
• (ii) a center axis bullet inlet port;
• and
• (iii) an offset return gas port;
• (c) a target-side wall on the target oriented end of the plenum enclosure, the target-side wall comprising a center axis bullet exit port;
• and
• (d) at least one chamber wall positioned within the plenum enclosure between the barrel-side wall and the target-side wall, the at least one chamber wall comprising a center axis bullet pass-through port and a concentric buffer wall generally perpendicular to a bullet direction of travel, the concentric buffer collecting, storing, and redirecting expanding gas from behind a passing bullet back from the plenum enclosure to the offset return gas port of the barrel-side wall;
• wherein the expanding gas is directed through the return gas port into the gas tube and is conducted to the receiver of the firearm to cycle the bolt.