Cmmg Uppr Endvr 200 Mk4 20" 6mm Arc

The CMMG Upper Endeavor 200 MK4 20" 6mm ARC upper receiver is a precision-engineered platform designed for shooters who demand superior accuracy and velocity in a modern intermediate cartridge. The 6mm ARC caliber delivers balanced performance for medium-range engagements, offering reduced recoil and wind drift compared to larger calibers while maintaining energy retention beyond 600 yards. The 20-inch barrel length optimizes muzzle velocity and sight radius, making this upper receiver assembly suitable for precision rifle applications, competitive shooting, and field training scenarios.

Built on CMMG's proven Endeavor platform, this MK4 variant incorporates rugged construction principles familiar to operators and serious shooters. The 6mm ARC chambering has gained traction among precision rifle competitors and hunters seeking an efficient medium-range cartridge that reduces target impact and shooter fatigue compared to 308 Winchester or 223 Remington alternatives. The upper receiver configuration allows compatibility with standard AR-pattern lower receivers, enabling shooters to leverage existing infrastructure while upgrading to a caliber optimized for mid-range accuracy demands.

This build is purpose-built for precision-focused shooters—competitive marksmen, dedicated hunters, and tactical training professionals—who value ballistic efficiency and repeatability. The 20-inch barrel-to-caliber pairing maximizes the 6mm ARC's velocity potential while maintaining practical handling weight and profile, making it effective for range work, field competitions, and training environments where consistent long-distance performance matters.