BSF Barrels AR-15 Barrel, 6mm ARC. Carbon fiber sleeve around 416R stainless steel to improve heat resistance and stiffness without adding excessive weight. Features a 6 groove button rifling and an 11 degree target crown. Barrel is chambered in 6mm ARC and threaded 5/8-24 with a twist rate of 1-7.5. Color is Gray with a carbon fiber sleeve and stainless steel core. Suitable for AR-15 platform and comes in a box package.