CMC Barrels AR15 barrel was designed to be the perfect addition to your SBR or pistol build. Made from 4150 Chrome Moly Vanadium, SOCOM barrel profile, coated in H&M Blacknitride+ for increased wear resistance, chambered in .223 Wylde so that you can feed it both .223 and 5.56 NATO ammo. Featuring M4 feed ramps for reliability; 11-degree match crown for increased accuracy; bottom dimple for easy gas block install and alignment; SOCOM Barrel profile; pistol gas system; air gauged. Gas block diameter: .750" with a gas block journal length of 1.13".