 The 6mm bullet is slightly wider, and the standard 6×35mm bullet slightly heavier, than the standard 5.56mm bullet ( versus ).Fired from a 10-inch (250 mm) barrel, KAC claims that the 6×35mm cartridge reaches a muzzle velocity of , slightly faster than the muzzle velocity of a 5.56 mm cartridge fired from a similarly short barrel.The larger diameter, shorter 6 mm cartridge is optimized for these shorter barrel lengths, and would perform less efficiently from rifle-length barrels.