The CMMG Resolute MK4 Upper Group (brand part no. 30BC40A-AB) is a fully assembled AR-platform upper chambered in .300 AAC Blackout, built around a 16.1-inch barrel with a 1:7 twist rate to stabilize the full range of subsonic and supersonic .300 BLK loads. Finished in matte black and measuring 31.2 inches overall, this upper ships fully assembled but without a bolt carrier group or charging handle, so you will need to add those separately to complete the build.

Key Specifications

• Chambered in .300 AAC Blackout.
• Built with a 1:7 twist rate for a wide range of .300 BLK bullet weights.
• Features a 16.1-inch barrel.
• Measures 31.2 inches overall.
• Finished in matte black.
• Sold as a fully assembled upper group.
• Part of CMMG’s Resolute MK4 line.
• Built on the AR-platform upper receiver pattern for direct fitment to a compatible lower.
• Ships without a bolt carrier group or charging handle.

Frequently Asked Questions

Does this upper include a bolt carrier group? No, it ships without a BCG or charging handle; both must be added separately.

What is the twist rate? 1:7, suited to a wide range of .300 Blackout bullet weights.

How long is the barrel? 16.1 inches.

Buy the CMMG Resolute MK4 Upper Group in .300 Blackout

Add a ready-to-run .300 Blackout upper to your build. Order the CMMG Resolute MK4 Upper from CMMG in our AR15 uppers selection, shipped fast from our Lubbock, Texas gun shop.