I've been converting .348 win brass to 45-75 win brass for a lot of years. Needing a few more cases I broke out the gear and went to work. Because I have the dies my process is cut off most of the neck of the 348 case with a dremel and debur. Run through 38-55 expander. Run through 40-65 expander. Run through 45-70 expander. Trim, lube, size, fire form. Casse loss occurs with the 45-70 expander. I have on my bench, which I did not have the last time I went through the process, is a lee universal case mouth expander (middle die in pic). Using this before the 45-70 expander resulted in 0 case loss.
Attachment 313789
Attachment 313790
Attachment 313791