Barrel: 416R Stainless steel. Chambered in 223 Wylde, with a 1:7 twist rate, M4 barrel extension, and a rifle-length gas system. Barrel is is finished off with a PSA 15" Lightweight M-Lok free float rail, .750 gas block, and A2 flash hider. Upper: 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 Carrier Group: 5.56mm Bolt Carrier Group is Nickel Boron coated and features a C158 bolt. The gas key is hardened and secured with Grade 8 fasteners, and is staked per Mil-Spec.