The CMMG Resolute MK4 Upper Group (brand part number 64BCF88AB) is chambered in 6.5 Grendel, a flat-shooting round at medium to long ranges that draws on the efficient ballistic performance common to many 6.5mm bullet designs. Built by CMMG with a 16.1-inch barrel, this upper is built on the Mk4 platform and works with any standard AR15 lower group, giving shooters a long-range-capable caliber option without leaving the AR15 platform.

Key Specifications

• Chambered in 6.5 Grendel on the Mk4 platform.
• Barrel length is 16.1 inches.
• Twist rate is 1:8, matched to 6.5 Grendel bullet weights.
• Barrel material is 416 stainless steel with a salt bath nitride finish.
• Built to work with any standard AR15 lower group.

Frequently Asked Questions

Why choose 6.5 Grendel over 5.56 NATO? 6.5 Grendel offers a flatter trajectory and more retained energy at medium to long range than standard 5.56 NATO loads.

Will this fit a standard AR15 lower? Yes, this upper works with any standard AR15 lower group.

Buy the CMMG Resolute MK4 6.5 Grendel Upper Group

Stretch your AR15’s effective range with a proven 6.5mm cartridge. Order this AR-15 upper from our Lubbock, Texas gun shop for fast, insured shipping to your door.