Barrel: This Chrome Moly vanadium 4150V barrel is chambered in .300 AAC Blackout with a 1:8" twist, M4 barrel extension, and a pistol-length gas system. It is finished off with a .750" diameter gas block, PSA 15" Lightweight M-Lok Partial Picatinny free float rail, and an A2 Flash Hider. Upper: The forged 7075-T6 A3 AR upper is machined to MIL-SPECS and hard coat anodized. These uppers are made for us right here in the USA by a mil-spec manufacturer. Bolt: Bolt is made of Mil-spec shot-peened Carpenter 158 steel. Gas key is secured with grade 8 fasteners and staked per mil-spec. Bolt carrier is nitride treated.