Barrel: 7.5" Chambered in 5.56 NATO with a 1:7 twist rate, M4 barrel extension, and a pistol length gas system. This nitride barrel is finished off with a DPMS Quad Rail free-float rail, .750" diameter low profile gas block, and an A2 flash hider. Upper: Forged 7075-T6 A3 AR upper is made to MIL-SPECS and hard coat anodized black for durability. 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 parkerized outside, and chrome lined inside.