CMMG Resolute Mk3 8.6 Blackout 16.1 inch Upper Receiver 1-3 Twist 5/8 x 24 CMMG ZEROED Muzzle Brake Cerakote Armor Black. 6 BLK in one word it would "Versatile". 8.6 BLK learned from the successes of it's smaller older brother 300 BLK lending itself very well to subsonic suppressed use and excelling with supersonic ammo when hitting the target hard matters. There can be a lot of confusion with .308 AR platforms and compatibility CMMG has kept it simple by basing our Mk3 platform off the popular Gen 1 DPMS High-Pattern LR308 design which means greater parts availability and more customization potential. Available in seven different Cerakote finishes all CMMG Upper Groups come complete with bolt carrier group and ZEROED accessories. Specifications for CMMG Resolute Mk3 8.6 Blackout 16.1 inch Upper Receiver: Manufacturer: CMMG Caliber: 8.6mm Blackout Barrel Length: 16.1 in Barrel Twist Rate: 1-3 Threads per Inch: 5/8x24 Muzzle Device: ZEROED Muzzle Brake Finish: Cerakote Gun Type: Rifle Gun Make: CMMG Gun Model: CMMG Mk3 Barrel Material: 4140 Chrome Moly Vanadium Features of CMMG Resolute Mk3 8.6 Blackout 16.1 inch Upper Receiver Lifetime Quality Guarantee Package Contents: CMMG Resolute Mk3 8.6 Blackout 16.1 inch Upper Receiver ZEROED Mk3 Polymer Dust Cover ZEROED AR10/Mk3 Ambi Charging Handle ZEROED Muzzle Brake 8.6 BLK What firearm models does the manufacturer say CMMG Resolute Mk3 8.6 Blackout 16.1 inch Upper Receiver is compatible with? The manufacturer says that CMMG Resolute Mk3 8.6 Blackout 16.1 inch Upper Receiver is compatible with CMMG Mk3CMMG 33BFA0C-AB: Resolute Mk3 8.6 Blackout 16.1 inch Upper Receiver 1-3 Twist 5/8 x 24 CMMG ZEROED Muzzle Brake Cerakote Armor Black