CMMG MK4 Complete Upper Features The CMMG MK4 upper receiver assembly is machined from billet 6061 T6 aluminum giving it a stronger more rigid platform than a standard forged upper while allowing tighter tolerances throughout. Chambered for 5.56 NATO and .223 Rem the upper ships complete with a 14.5 inch steel barrel cut with a 1:7 inch twist rate that stabilizes a wide range of bullet weights from lighter varmint loads to heavier tactical rounds. This twist rate flexibility makes the MK4 a versatile choice for shooters who want to experiment with different ammunition without being limited by barrel twist. The steel barrel offers durability and heat resistance for sustained firing strings. Finished in a Coyote Tan Cerakote coating the MK4 upper offers a durable corrosion resistant finish along with a tan color that pairs well with many popular lower builds. CMMG designs the MK4 platform to drop onto any compatible AR-15 lower giving builders flexibility to mix and match components for a customized rifle. Billet construction also allows for refined ergonomics and a distinctive appearance compared to mil-spec forged uppers. This CMMG MK4 Complete Upper in Coyote Tan is available for sale at GrabAGun for builders looking to add a precision billet upper to their AR-15 platform. CMMG MK4 Complete Upper Specifications Manufacturer: CMMG Model: MK4 Complete Upper Caliber: 5.56 / .223 Rem Barrel Length: 14.5 Barrel Material: Steel Twist Rate: 1:7 Receiver Material: Billet 6061 T6 Aluminum Finish: Coyote Tan Cerakote Color: Coyote Tan Available At: GrabAGun