This YHM barrel features a 300 AAC Blackout Chamber. It is a 16" barrel with 1:8" twist rate. Constructed of 4140 chrome moly steel with a threaded muzzle (5/8"-24), the barrel is Melonited for ultimate surface protection. The melonite coating provides a thinner surface than chrome-lining, so bore friction is reduced for better accuracy. In addition, melonite is harder than chrome-lining providing a longer wear life. The YHM .300 BLK barrels are designed to perform with both subsonic (220 and 208 gr) and supersonic loads. The gas port has been tuned to lock the bolt open on the last round when using subsonic ammunition with a sound suppressor or supersonic ammo without a suppressor. This barrel is an excellent choice for a general purpose AR rifle build. It is perfectly suited for use at the range, in a 3-Gun match, or in the field pursuing game.