Hi Joe,
You must use 222 rem mag brass to make a 6x47. If you use 223 brass you will have a 6x45. I haven't found 222 rem mag brass to hard to find. I am not 100% sure but you prob could use 204 brass to get to a 6x47. I took my xp-100 pistol to the range today for the first time. Its in 6x47...