5.56mm May be the staple caliber of carbine-size AR15s but 22 ARC is the next generation of .22 caliber AR chamberings. Designed to provide consistent function from the AR-15 platform 22 ARC delivers 22-250 levels of ballistic performance in the Mk4 (AR15) lineup. - When full-size rifles are too cumbersome and pistols/SBRs don