DealBarrel: 4150V Chrome Moly Vanadium steel. Chambered in 5.56 NATO, with a 1:7 twist, M4 barrel extension, and a carbine length gas system. ** 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. from Palmetto State Armory (Product 777781B) |