Barrel: 416R Stainless steel. Chambered in 223 Wylde, with a 1:7 twist, M4 barrel extension, and a rifle length gas system. The barrel is finished off with a PSA 15" Hex Full Picatinny 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: Full-auto profile bolt carrier group. Shot-peened, mil-spec Carpenter 158 steel bolt. Gas Key Hardened to USGI Specifications, Fastened with Grade 8 screws, and Staked Per Mil-Spec. The carrier is an 8620 steel M-16 full-auto profile and is Nickel Boron coated.