Shop › CMMG BBL 300BLK 16.1" MR 4140CM SBN CMMG BBL 300BLK 16.1" MR 4140CM SBN $199.95 CMMG Barrel, 300 AAC Blackout, 16.1" Barrel, 1:7 Twist, Carbine 4140 CrMo Salt Bath Nitride Finish, 5/8"-24 TPI 30DF80A Quantity: Add To Cart Added! CMMG Barrel, 300 AAC Blackout, 16.1" Barrel, 1:7 Twist, Carbine 4140 CrMo Salt Bath Nitride Finish, 5/8"-24 TPI 30DF80A