6mm ARC
The 6mm Advanced Rifle Cartridge (6×38mm), or 6mm ARC for short, is a 6 mm (.243) caliber intermediate rifle cartridge introduced by Hornady in 2020, as a low-recoil, high-accuracy long-range cartridge, designed for use in the AR-15 rifle platforms at the request of a specialized group within the United States Department of Defense for its multipurpose combat rifle program. When compared to the military 5.56mm NATO platform, 6mm ARC is dimensionally incompatible regarding barrel, bolt and magazine components.