Rosco Bloodline 16" Heavy Barrel for AR-15 in 5.56 NATO. Crafted from 4150 chrome moly vanadium steel with a nitride finish. 1:7 twist, 16-inch length with carbine-length gas system. Features 1/2x28 muzzle threads, a .750 gas block journal, and an 11-degree crown. Made in the USA.