CMMG Resolute Mk4 Complete Upper Features The CMMG Resolute Mk4 Complete Upper Group runs on a traditional blowback operating system chambered in .22 LR giving AR-15 owners an affordable way to train on their existing lower receiver. Its 16.1-inch barrel is built from 4140CM steel with an SBN finish and a 1:16 twist rate matched to an M4 contour for a familiar profile and balance. The billet 6061 T6 aluminum upper receiver houses the bolt group and is paired with a CMMG EML M-LOK handguard giving shooters plenty of real estate to mount lights grips or other accessories. A CMMG Zeroed muzzle brake threaded 1/2x28 helps manage muzzle movement while the CMMG Zeroed ambidextrous charging handle keeps controls accessible for both right and left-handed shooters. Finished in a matte black cerakote the upper resists wear and corrosion through repeated range sessions and handling. At 3.85 pounds and 24 inches overall this upper swaps onto a compatible AR-15 lower to deliver low-cost low-recoil .22 LR practice without the wear and expense of centerfire ammunition. The combination of a blowback .22 LR action with standard AR-15 ergonomics makes this upper a practical training tool for building trigger control and familiarity with the platform. This CMMG Resolute Mk4 Complete Upper Group is available for sale at GrabAGun for AR-15 owners who want an economical rimfire conversion option. CMMG Resolute Mk4 Complete Upper Specifications Manufacturer: CMMG Model: Resolute Mk4 Complete Upper Caliber: .22 LR Operating System: Traditional Blowback Barrel Length: 16.1 Barrel Twist: 1:16 Barrel Material: 4140CM SBN Muzzle Device: CMMG Zeroed Muzzle Brake Muzzle Thread: 1/2x28 Upper Receiver: Billet 6061 T6 Aluminum Handguard: CMMG EML13.5 M-LOK Finish: Matte Black Cerakote Charging Handle: CMMG Zeroed Ambi Weight: 3.85 lbs Overall Length: 24 Available At: GrabAGun