The Rise Armament Complete 6mm ARC Upper in 18-inch Patriot Brown (Rise Armament part no. RA6ARCCUBRN18) is a fully assembled AR-15-pattern upper chambered in 6mm ARC, built around an 18-inch barrel with a 1:7 twist rate for stabilizing the heavier, high-BC bullets that make 6mm ARC a strong long-range option. Rise Armament finishes the barrel in a durable black Cerakote coating and dresses the upper in a Patriot Brown color scheme, giving it a distinct two-tone look. At 18 inches, the barrel comfortably clears the federal 16-inch rifle minimum, so it goes straight onto a rifle-configured lower with no NFA paperwork. This upper does not include a lower receiver.

Key Specifications

• Chambered in 6mm ARC, a long-range cartridge built around efficient, high-BC bullets.
• An 18-inch, 416R stainless steel barrel is button-rifled and air-gauge tested for accuracy.
• A 1:7 twist rate stabilizes the heavier, high-BC bullet weights common in 6mm ARC loads.
• Threaded 1/2×28 at the muzzle for compensators, brakes, or suppressor mounts.
• The barrel carries a black Cerakote finish for wear resistance.
• A 15.25-inch, free-floating skeletonized aluminum M-LOK handguard carries a continuous top Picatinny rail.
• The bolt carrier group uses a 9310 steel bolt finished in black nitride and is individually MPI tested.
• Runs a rifle-length gas system with a .750-inch gas block.
• Ships with a RISE ambidextrous charging handle for right- or left-hand operation.
• The upper’s furniture is finished in Patriot Brown for a distinct two-tone look.

Frequently Asked Questions

Does this upper include a lower receiver? No, this is a complete upper only; it needs to be paired with your own AR-15-pattern lower receiver.

What twist rate does the barrel use? A 1:7 twist, sized to stabilize the heavier bullet weights common in 6mm ARC loads.

What handguard does this upper use? A 15.25-inch, free-floating skeletonized aluminum M-LOK handguard with a continuous top Picatinny rail.

Buy the Rise Armament Complete 6mm ARC Upper, 18-inch Patriot Brown

Order it from our Lubbock, Texas gun shop for fast, direct shipping and drop this upper onto your next 6mm ARC build. Browse more AR15 uppers to compare calibers and finishes.