RE: opening up dies
RWK, we are just discussing the possibility, the 243 Winchester is shorter from the head of the case to the shoulder by .168 thousands than the 257 Roberts, meaning the 257 Roberts is a necked down 7X57 Mauser, the 243 Winchester is the same length from the head to shoulder as the 308 Winchester and the 7MM/08, there has to be a 257/08 out there somewhere, could be expensive, so are the tools that could be required to alter the die.
F, Guffey