The OH 18-Inch 6mm ARC Complete AR-15 Upper Receiver (brand part no. CU09) takes the AR-15 platform to the next level with a precision setup built for shooters who demand accuracy, reliability, and extended-range performance. It’s built around an 18-inch 416R stainless steel barrel with a 1:7.5 twist rate that stabilizes the full range of 6mm ARC projectile weights, delivering the accuracy long-range shooters and hunters want. The free-float M-Lok handguard keeps the platform lightweight and rigid while giving shooters an easy way to mount lights, bipods, and other accessories, and a nitride-finished bolt carrier group keeps cycling smooth under demanding use. Built to Mil-Spec standards and shipped complete with a charging handle and bolt carrier group, this upper is ready to install on any Mil-Spec AR-15 lower for a precision rifle, hunting setup, or versatile all-around build.

Key Specifications

• Chambered in 6mm ARC for flat-shooting, long-range performance out of an AR-15 platform.
• An 18-Inch 416R Stainless Steel Barrel balances velocity and accuracy for extended-range shooting.
• A 1:7.5 Twist Rate stabilizes the full range of common 6mm ARC bullet weights.
• The HBAR Barrel Profile adds rigidity and helps manage heat during extended strings of fire.
• A 5/8×24 Muzzle Thread accepts standard muzzle devices and suppressors for 6mm ARC.
• A Free-Float M-Lok Handguard keeps the platform lightweight while providing a stable mounting surface for accessories.
• An 18-Inch Handguard Length gives shooters plenty of real estate for lights, bipods, and grips.
• The Nitride-Finished Bolt Carrier Group ensures smooth cycling and long-term durability.
• A Rifle-Length Gas System softens the felt recoil impulse for a smoother shooting experience.
• Built to Mil-Spec Standards and shipped Complete with a charging handle and bolt carrier group, ready to install on any Mil-Spec AR-15 lower.

Frequently Asked Questions

What lower receivers is this upper compatible with? Any Mil-Spec AR-15 lower receiver.

Does this upper come with a bolt carrier group and charging handle? Yes, it ships complete and ready to install.

What is 6mm ARC best suited for? Long-range precision shooting and hunting, thanks to its flat trajectory and efficient case design.

Buy the OH 18-Inch 6mm ARC Complete AR-15 Upper Receiver

Whether you’re building a precision rifle, a hunting setup, or a versatile AR platform, this 6mm ARC upper delivers the performance to stretch your rifle’s capabilities. Order it from our Lubbock, Texas gun shop for fast, insured shipping to your FFL, and pair it with your AR-15 upper receiver build.