Barrel: 4150V Chrome Moly steel. Chambered in 5.56 NATO, with a 1:7 twist, M4 barrel extension, and a carbine-length gas system. Barrel is is finished off with a standard handguard, F-Marked gas sight base, and A2 flash hider. Upper: Forged 7075-T6 A3 AR upper is machined to MIL-SPECS and hard coat anodized, features a forged upper receiver. These uppers are made for us right here in the USA by a mil-spec manufacturer. Bolt: Full-auto profile bolt carrier group. Milspec 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 Build Kit: Includes Classic M4-Style Stock, A2 Pistol grip, Classic Lower Parts Kit and Mil-Spec diameter 6-position buffer tube assembly. Everything you need to finish your stripped lower. ** These uppers will have cosmetic blemishes that do not affect function. This may include, but is not limited to, forging marks under the finish, scratches, slight variation in the finish color coat.