Faxon Firearms Duty Series, Big Gunner, 1:3 Twist Barrel, 8.6 Blackout, 16, Carbine Length Gas System, Fits AR-10, Nitride Finish, Black 10A863C16NGQ As with all Faxon Barrels" these 8.6 BLK barrels are machined from raw bar stock in their greater Cincinnati Facility. Faxon 8.6 BLK barrels are fully stress-relieved" air-gauge tested" Magnetic Particle Inspected" and 11-degree target crowned to ensure superior accuracy. Constructed of 4150 CMV" each barrel goes through a battery of tests at each operation until finished in Nitride and final inspected.