Description
Drop the CMMG Upper Receiver Assembly Mk4/AR-15 onto any mil-spec AR-15 lower and you have the foundation for a complete rifle or pistol-caliber build. Machined from forged 7075-T6 aluminum and finished in a low-glare Tungsten Cerakote, this stripped upper ships with the factory-installed forward assist and ejection port door assembly, so it arrives ready to be paired with the barrel, bolt carrier group, and charging handle of your choice.
The Mk4 receiver carries an enlarged ejection port sized to clear the taller case heads of common pistol-caliber AR-15 builds in 9mm Luger, 10mm, .40 S&W, and .45 ACP, in addition to standard 5.56x45mm NATO rifle setups. That extra clearance makes the same upper a versatile foundation for a 5.56 NATO duty rifle or a pistol-caliber carbine without swapping uppers. The standard AR-15 Picatinny rail on top accepts any optic, iron sight, or magnifier mount, and the upper’s external geometry matches mil-spec handguards for free-float or drop-in fitment.
Built to CMMG’s Mk4 / AR-15 specification, this Tungsten upper is offered here as the stripped upper receiver assembly only. No barrel, bolt, bolt carrier, charging handle, handguard, muzzle device, lower receiver, or sights are included.
