Most AR15s use a direct impingement gas operating system. Simply put, that means some of the gas from each fired round is directed through a tube running above the barrel. It blows out of the tube directly against the bolt carrier, causing the bolt assembly to move back to cycle the acti...
The bolt carrier group, moving backward and forward in this smoothly automated fashion, is the mechanized soul of your AR-15. It includes the direct gas impingement system. After the bullet is fired, it uses the gases released to power the BCG through its cycle. The BCG produces the smooth...