Patent ID: 6931978

Claim:
An automatic firearm operating on the basis of a blow-back action, said firearm having: 1) a barrel with a breech and a chamber for receiving a round to be fired, 2) a receiver into which the barrel is mounted, and 3) a unitary bolt carrier assembly including a bolt, a firing pin and a carrier fixed for movement as a unit, said firing pin being axially aligned with said chamber, said assembly being slidingly mounted in said receiver for shifting during cycling of the weapon between a first position wherein the bolt is in-battery against said breech and a second position wherein said bolt carrier assembly is fully removed from the breech while cycling in a full blowback mode; 4) a return spring, seated within the weapon for urging the bolt carrier assembly towards the in-battery position when the weapon is cycling; and 5) weight means slideably mounted within a containment space that travels with the bolt carrier assembly for sliding motion with respect to said bolt carrier assembly, whereby, when the weapon is cycling with the bolt carrier assembly having moved rearwardly away from its first position against said breech, to said second position, said weight means will slide away from the breech in its containment space and so remain on the return stroke of the cycle until the bolt is again at the in-battery position, and when the bolt carrier assembly has returned to the in-battery position, the weight means will slide forwardly in its containment space towards the breech to the forward limit of its travel, bearing against the bolt carrier assembly when it comes to the in-battery position and thereby increasing the dwell-time for the bolt when it is in the in-battery position during automatic firing, allowing time to ensure that the firing pin will effectively advance to fire a round.