Barrel: 4150V chrome moly steel. Chambered in 5.56 NATO, with a 1:7 twist rate, M4 barrel extension, carbine-length gas system, and nitride treated for accuracy and durability. A2 profile barrel is finished off with a PSA 9" Lightweight M-Lok free-float rail, .750" low-profile gas block, and A2 Flash Hider. Upper: Forged 7075-T6 A3 AR upper is hard coat anodized. These uppers are made for us right here in the USA! Bolt: Full-auto profile bolt carrier group. Shot-peened, mil-spec Carpenter No. 158A(R) 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. Pistol 7075-T6 buffer tube is hardcoat anodized and is fitted with an SB Tactical SBA3 Adjustable Pistol Brace, Magpul Grip, and Enhanced Polished Trigger (EPT). **FFL Required