CMMG Resolute Mk4 Upper | 6.5 Grendel | 16.1 in

The CMMG Resolute Mk4 upper group is a complete AR-15 upper built on CMMG’s Mk4 platform and chambered in 6.5 Grendel for efficient medium-to-long-range ballistics. It ships complete with a bolt carrier group and CMMG ZEROED accessories including an ambidextrous charging handle, polymer dust cover, and a CMMG ZEROED muzzle brake. The upper uses a direct impingement operating system and pairs with any standard AR-15 lower group.

Applications for this upper include precision-oriented target work at extended ranges and medium‑range hunting where 6.5mm ballistics offer improved sectional density and energy retention. The package is intended for users seeking a ready-to-install, accuracy-focused AR-15 upper without needing to source separate BCG or muzzle devices.

Product Specifications

• The platform is built on the Mk4 architecture.
• The caliber is specified as 6.5 Grendel.
• The operating system is Direct Impingement.
• The barrel length is listed as 16.1.
• The barrel twist rate is 1:8.
• The barrel contour is noted as MT.
• The barrel material is 416SS SBN.
• The muzzle device is the CMMG ZEROED Muzzle Brake.
• The muzzle thread is 5/8 x 24.
• The gas port location is listed as Rifle.
• The gas block is 0.750 Non-Adjustable.
• The upper receiver is Billet 6061 T6 Aluminum.
• The hand guard is the CMMG EML15 M-LOK.
• The finish is specified as Cerakote Standard.
• The charging handle is the CMMG ZEROED Ambi.
• The listed overall length is 25.
• The UPC for this item is 810097504738.

This Resolute Mk4 upper brings a complete, install-ready solution for shooters who want a 6.5 Grendel option on a standard AR-15 lower. The combination of a 16.1-length barrel, a well-regarded 1:8 twist, and CMMG’s ZEROED accessories makes it a practical choice for deliberate, accuracy-focused use while minimizing parts sourcing and assembly time.