338 ARC brings .338-caliber authority to the small-frame AR, ideal for short-range big-game hunts or sub-50-state hog work. Arm or Ally’s 16″ and 18″ 4150 CMV barrels feature a 1:9 twist to stabilize 200- to 225-grain bullets, carbine-length gas for reliable cycling, and 5/8-24 threads ready for suppressor-friendly brakes. Because 338 ARC runs stout pressures, we include head-spaced bolts with reinforced lugs and offer extra-power extraction springs for trouble-free ejection. Mated to our billet uppers and free-float rails, these barrels transform the AR-15 into a hard-hitting platform without the weight penalty of an AR-10. If you need big-bore stopping power in a compact package, 338 ARC is the ticket—and we have the barrels to get you there. Not sure which caliber suits your mission or state regs? We’re always here to help with builder-tested advice, gas-port data, and complete parts bundles to bring your next AR-15 project to life.