The CMMG 300 AAC Blackout Barrel features 1 in 7" twist rifling and a carbine length gas system. The muzzle is threaded 5/8"-24 for use with muzzle brakes, flash suppressors, or sound suppressors. Gas block and gas tube not included. The barrel is composed of Chrome Moly Steel and finished inside and out with CMMG's durable salt bath nitride finish. This treatment produces an extremely hard, slick surface on steel that resists carbon adhesion and increases corrosion resistance, making for easier cleaning and maintenance. Nitriding converts the steel's surface without any build-up, retaining all of the benefits of traditional chrome lining without suffering the accuracy degradation commonly encountered due to uneven application of chrome inside the barrel's bore. Notes: Suitable for use with Subsonic or Supersonic loads, either Suppressed or Unsuppressed