moeben; You can easily make your 204 ruger brass into 6x47. You need to do an intermediate step so as not to collapse the shoulder. Use a 222 mag or even a 222 Rem expander button first, and then got to 6mm after that. Chamfer the mouth of the case inside, and a good light coat of lube inside helps as well. Final step is a pass through the 6x47 FL die to set the shoulder back a hair, since the 204 case is slightly longer to the shoulder than is the 222Mag/6x47 case. BTW, New brass works best! Regards, Eagleye.