Barrel: 10.5" Chrome Moly vanadium steel, melonite treated for durability and chambered in 5.56 NATO with a 1 in 7" twist rate. Carbine length gas barrel is finished off with a PSA 9" Lightweight M-Lok Rail, a 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.