CMMG LR-308 Resolute 100 Mk3 Upper Receiver Assembly, .308 Win, 16" Barrel, M-LOK Handguard

The CMMG LR-308 Resolute 100 Mk3 upper receiver assembly brings serious .308 Win firepower to your AR platform build. This complete upper combines a 16-inch stainless barrel with a modern M-LOK handguard, direct impingement action, and everything you need to get on target—no piecing together parts from different manufacturers. Built on the proven Gen 1 DPMS High-Pattern LR308 platform, the Resolute 100 Mk3 gives you straightforward compatibility with established parts ecosystems and genuine room to customize without the guesswork that haunts some .308 AR designs.

CMMG equips this upper with its own ZEROED ecosystem of components: the included dust cover, ambidextrous charging handle, and muzzle brake are all matched to the .308 platform and pre-assembled. The billet aluminum upper receiver is machined from 7075 T6 stock and finished in standard Cerakote, delivering durability and clean lines. The 416 stainless steel barrel wears a 1:10 twist optimized for mid-weight .308 rounds, rides a non-adjustable 0.750 gas block tuned for rifle-length gas port placement, and threads 5/8x24 for suppressor compatibility or alternative muzzle devices. The EML15 M-LOK handguard gives you flexibility for mounting optics, lights, and other field gear.

This is a purpose-built upper for shooters assembling a modern .308 carbine—whether for medium-range hunting, precision rifle training, or a dependable semi-auto setup. At 5.8 pounds and 28.3 inches long, it strikes a practical balance between handling and barrel performance. Drop it on a matching lower receiver and you're ready to run.

Key Features

• Complete upper assembly—no stripped receiver guesswork
• CMMG ZEROED bolt carrier group, dust cover, and ambi charging handle included
• 16-inch 416 stainless steel barrel with 1:10 twist and rifle-length gas port
• M-LOK handguard for easy accessory mounting
• CMMG ZEROED muzzle brake (5/8x24 thread for suppressor-ready flexibility)
• Billet 7075 T6 aluminum upper receiver with standard Cerakote finish
• Gen 1 DPMS LR308 platform—widely supported, proven compatibility
• Non-adjustable 0.750 gas block tuned for the caliber

Specifications

Frequently Asked Questions

What lower receiver is this compatible with?

The Resolute 100 Mk3 upper is built on the Gen 1 DPMS High-Pattern LR308 platform, so it will mate with LR308-pattern lower receivers—not standard AR-15 lowers. Confirm your lower's platform before ordering.

Is the muzzle brake removable or can I add a suppressor?

The included CMMG ZEROED muzzle brake threads onto the 5/8x24 barrel, so you can unscrew it to mount a suppressor or other muzzle device with the same thread pitch.

What's included in the box?

This upper arrives complete with the bolt carrier group, dust cover, ambidextrous charging handle, and muzzle brake already installed and ready to function. You'll need a lower receiver and fire control group to complete a rifle.

Is the gas block adjustable?

No—this assembly uses a fixed 0.750 non-adjustable gas block tuned for the .308 platform and rifle-length gas port. It's set for reliable direct impingement performance with standard .308 ammunition.