Barrel: 416R stainless steel. Chambered in 5.56 NATO, with a 1/7 twist, M4 barrel extension, and a mid-length gas system. Pencil profile barrel is finished off with a PSA 13.5" lightweight keymod free-float rail, .625" 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: Full-auto profile bolt carrier group. Shot-peened, mil-spec Carpenter No. 158® steel bolt. Gas Key Hardened to USGI Specifications, Fastened with Grade 8 screws, and Staked Per Mil-Spec. 8620 steel M-16 profile carrier is chrome lined and phosphate coated. Lower: These forged lowers are quality made using 7075-T6 aluminum and are marked "MULTI" for caliber. Finish is hardcoat anodized. Mil-spec diameter 7075-T6 buffer tube is hardcoat anodized, has 6 adjustment positions, is fitted with a PSA M4 Carbine Stock.