Patent ID: 9032860
Filing Date: 2015-05-19
Classification: F41A,F41C

Abstract:
1. An upper receiver assembly for use with an AR15-type lower receiver in which the lower receiver attaches to an upper receiver assembly by way of a forward pivot pin and a rearward takedown pin, comprising: a monolithic upper receiver and forearm housing configured for operable mating engagement with a lower receiver assembly, the upper receiver and forearm housing including a first lug for connection to the lower receiver using the takedown pin; a barrel having a breech end, a muzzle end, and a bore axis; a barrel trunnion at the breech end having a second lug for direct connection to the lower receiver using the pivot pin; a gas block positioned on the barrel; a bolt carrier assembly including a longitudinal slot and rail engagement with the upper receiver assembly on which the bolt carrier assembly slidably reciprocates; a long-stroke gas-piston actuation system having a longitudinal axis parallel to and offset from the bore axis, the gas actuation system including a gas tube extending rearwardly from the gas block and a piston extending forwardly from the bolt carrier assembly; and a recoil spring assembly housed within the monolithic upper receiver and forearm housing and extending coaxially with the longitudinal axis of the gas-piston actuation assembly, wherein the barrel trunnion is configured for engagement with the upper receiver and forearm housing with longitudinal keyway features, one of a keyway or engagement rail being on the barrel trunnion and the other on the upper receiver and forearm housing; and wherein the gas block is configured for engagement with the upper receiver and forearm housing with longitudinal keyway features, one of a keyway or engagement rail being on the gas block and the other on the upper receiver and forearm housing.