CMMG Resolute MK4 6mm ARC Upper Receiver Assembly 16.1" – AR-15 Platform

The CMMG Resolute MK4 6mm ARC upper receiver assembly delivers 6mm ARC chambering in a 16.1" barrel configuration, designed for AR-15 platform lowers. This upper provides extended effective range and flatter trajectories compared to traditional 5.56 NATO, while maintaining compatibility with standard AR-15 lower receivers. The 6mm ARC chambering offers excellent ballistic performance for precision shooting and hunting at extended distances.

Built with CMMG's MK4 design, this upper features a medium-taper 4140 chrome moly steel barrel with salt bath nitride finish for corrosion resistance and barrel life. The free-float handguard provides a rigid mounting platform for accessories and optics. Compatible with standard AR-15 BCG and charging handle (typically included with complete upper assemblies—verify contents). Installation requires basic AR-15 assembly knowledge and appropriate headspacing verification.

• Caliber: 6mm ARC
• Type: Complete Upper Receiver Assembly
• Compatible Lower: AR-15 / MULTI
• Barrel Length: 16.1"
• Material: 4140 Chrome Moly Steel Barrel, 7075-T6 Aluminum Receiver
• Finish: Black Salt Bath Nitride Barrel, Type III Hardcoat Anodized Receiver
• Includes: Upper receiver assembly with barrel and handguard (verify complete contents with manufacturer)
• Installation: Fits standard AR-15 lower receivers, requires compatible BCG and charging handle