Barrel: Chrome-moly vanadium steel, phosphate coated, chrome lined barrel chambered in 5.56 NATO, with a 1:7 twist rate, M4 barrel extension, and a mid-length gas system. The tapered profile barrel is finished off with a PSA 15" Guardsman Hex Full Picatinny M-Lok free-float rail, pinned low-profile gas block, and A2 flash hider. Upper: Forged 7075-T6 A3 AR upper is machined to MIL-SPECS and hard coat anodized. Uppers include forward assist and dust cover. These uppers are made for us right here in the USA by a mil-spec manufacturer. Bolt Carrier Group: Full-auto profile bolt carrier group. Shot-peened, HPT, mil-spec Carpenter 158 steel bolt. Sprinco gas rings. Gas Key Hardened to USGI Specifications, Fastened with OCKS screws, and Staked Per Mil-Spec. The carrier is an 8620 steel M-16 full-auto profile. Phosphate coated and chrome lined.