The 6 mm Advanced Rifle Cartridge (6×38mm), or 6mm ARC for short, is a 6mm (.243) caliber full-power rifle cartridge introduced by Hornady in 2020, as a low-recoil, high-accuracy long-range cartridge designed for the AR-15 platform. All you need is a new barrel, magazine and bolt to convert AR-15 5.56/.223 rifle into the 6mm ARC. The 6mm ARC utilizes the same bolt head size as the 6.5mm Grendel, and 6.5mm Grendel AR-magazines have also been used successfully with the 6mm ARC.
The Moriarti Armaments AR-15 21″ 6MM ARC Match Grade Stainless Steel HBAR Upper Assembly comes complete with a MATCH GRADE Stainless Steel 416R Barrel, low profile Steel .875 Gas Block with Nitride Finish and a Stainless Steel Gas tube. Upper is finished off with a Free Float MLOK Handguar..The Moriarti Armaments AR-15 21″ 6MM ARC Match Grade Stainless...$699.95