6 mm XC (also known as 6XC) is a fairly new rifle cartridge, similar to the 6x47mm Swiss Match, that was developed specifically for NRA High Power match shooting by 11-time NRA High Power National Champion David Tubb. It is touted as being one of the most accurate long-range 6 mm rounds in the world that is designed for repeating rifles. Originally, the case for this wildcat cartridge had to be formed from .22-250 brass, but it is now commercially available.