Barrel: Chambered in 300AAC Blackout with a 1:8 twist rate, M4 barrel extension, and a pistol gas system. This barrel features a phosphate finish for accuracy and durability. It is finished off with a PSA 7" Lightweight Hex M-Lok rail, .750" diameter low profile gas block, and an A2 flash hider. Upper: Forged 7075-T6 A3 AR upper is machined to MIL-SPECS and hard coat anodized. These Left-handed uppers are made for us right here in the USA by a mil-spec manufacturer. Bolt: Full-auto profile left-handed bolt carrier group. 9310 steel bolt, Shot Peened, Gas Key Hardened to USGI Specifications, Fastened with Grade 8 screws, and Staked Per Mil-Spec. 8620 steel M-16 profile carrier.