CMMG Resolute MK4 6.5 Grendel 16.1" Complete Upper Group - Armor Black

The CMMG Resolute MK4 Complete Upper Group is purpose-built around the 6.5 Grendel cartridge, delivering flat-shooting, long-range-capable performance from a familiar AR-15 footprint. Built on CMMG's proven Mk4 platform, this complete upper is engineered to drop onto any standard AR-15 lower receiver, turning a host lower into a hard-hitting medium- to long-range rifle.

At the core of the Resolute MK4 is a 16.1" barrel machined from 4140CM steel with a 1:8 twist rate and a medium-taper contour - a combination optimized to stabilize the full range of 6.5 Grendel bullet weights. The barrel is finished with CMMG's signature Radial Brake muzzle device, which helps tame recoil and keep the optic on target during follow-up shots.

The upper receiver is forged from 7075-T6 aluminum in a classic M4-type profile and coated in Cerakote Armor Black for a durable, corrosion-resistant, and non-reflective finish. A free-float M-LOK handguard surrounds the barrel, providing a lightweight, modular platform for mounting accessories such as lights, lasers, bipods, and forward grips.

Running a time-tested direct impingement gas system, the Resolute MK4 upper delivers the reliability and controls AR-15 shooters expect. It installs on any mil-spec AR-15 lower receiver group and ships ready to pin and go. The complete upper group measures 25" overall and weighs approximately 4.3 lbs.