CMMG Resolute MK4 .300 Blackout 16.1" Complete Upper Group - Black

The CMMG Resolute MK4 complete upper group brings CMMG's proven Mk4 AR-15 platform to .300 Blackout shooters, delivering a turn-key assembly that mates to any mil-spec lower receiver. Purpose-built around the strengths of the .300 BLK cartridge, this upper supports both subsonic and supersonic loadings from a single barrel, making it a versatile choice for suppressed home-defense setups and general range work alike.

At the core of the build is a 16.1-inch barrel with a 1:7 twist rate, a configuration well-suited to stabilizing the wide range of bullet weights used in .300 Blackout. The upper receiver is machined from billet 6061 T6 aluminum and finished in CMMG's standard black Cerakote for corrosion and wear resistance. CMMG's EML15 M-LOK handguard wraps the barrel, providing a slim, lightweight platform for mounting accessories, while a ZEROED charging handle rounds out the controls.

This upper ships ready to mount on any standard AR-15 lower, with an overall assembly length of approximately 25 inches and a weight near 4.1 lbs. Whether the goal is a quiet, suppressed .300 BLK rifle for home defense or a supersonic hunting and range platform, the Resolute MK4 upper provides a durable, optics-ready foundation.