CMMG Resolute MK4 Upper — .300 AAC Blackout 16.1″

The CMMG Resolute MK4 Upper Group is a partially assembled AR-15 upper built for .300 AAC Blackout with a 16.1-inch barrel. It is supplied without a bolt carrier group or charging handle so builders can complete the assembly to their specifications. The steel barrel features a matte black finish and a 1:7″ twist rate for stabilization of common .300 Blackout projectiles. The package includes a CMMG EML 15 M-LOK free-float handguard and a non-adjustable .750 gas block with 1/2-28 muzzle threads fitted for an A2-style flash hider.

Key Specifications

• The caliber is .300 AAC Blackout.
• The barrel length is 16.1 inches.
• The rate of twist is 1:7″.
• The barrel material is steel.
• The barrel finish is matte black.
• The handguard is a CMMG EML 15 M-LOK free-float unit.
• The muzzle uses 1/2-28 threads and is fitted with an A2-style flash hider.
• The gas system includes a non-adjustable .750 gas block.
• Configuration is a partial upper group supplied without a bolt carrier group or charging handle.
• Designed for AR-15-platform lowers.

This Resolute MK4 upper provides a straightforward, build-friendly foundation for an AR-15 in .300 AAC Blackout. Its 16.1-inch steel barrel, proven 1:7″ twist and M-LOK free-float handguard make it suitable for a range of practical applications where component selection and customization matter. For builders who want to complete an upper with selected BCG and controls, this assembly is a reliable starting point.

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