CMMG Resolute Mk4 Complete Upper Features The CMMG Resolute Mk4 Complete Upper is built on a 4140CM steel barrel measuring 16.1 inches with a 1 in 7 twist rate a combination well suited to stabilizing a wide range of 5.56x45mm NATO bullet weights. A direct impingement operating system drives the action keeping the upper compatible with the broad universe of standard AR-15 components and ammunition. The barrel features a nitride finish for corrosion resistance and comes fitted with a CMMG ZEROED muzzle brake threaded at 1/2x28 helping manage recoil and muzzle rise during rapid strings of fire. A non adjustable .750 inch gas block sits at the mid length gas position contributing to reliable cycling across a range of ammunition. The billet 6061 T6 aluminum upper receiver is wrapped in a CMMG EML15 M-LOK handguard giving builders mounting space for lights grips and other accessories along the full length of the forend. A durable Cerakote finish in matte black protects the upper and barrel from the elements and daily wear. Every Resolute Mk4 Complete Upper ships with a bolt carrier group and a CMMG ZEROED ambidextrous charging handle already installed meaning the builder only needs a compatible lower to complete the rifle. At 4.3 pounds and 25 inches overall this upper suits AR-15 builders who want a complete drop in upper group from an established manufacturer without sourcing individual components separately. CMMG Resolute Mk4 Complete Upper Specifications Manufacturer: CMMG Model: Resolute Mk4 Complete Upper Caliber: 5.56 / .223 Rem Operating System: Direct Impingement Barrel Length: 16.1 Barrel Material: 4140CM Steel Barrel Twist: 1:7 Barrel Finish: Matte Black Muzzle Device: CMMG ZEROED Muzzle Brake Muzzle Thread: 1/2x28 Gas System: Mid Length Non-Adjustable .750 Handguard: CMMG EML15 M-LOK Upper Receiver: Billet 6061 T6 Aluminum Charging Handle: CMMG ZEROED Ambi Weight: 4.3 lbs Overall Length: 25 Available At: GrabAGun