British cases for the .500 already have very thin rims to the extent that you have to be very careful not to tear them off with the shell holder when extracting from the die even with prober lubrication.

It may be worth getting someone to make you a 360 degree shell holder ( female threaded collar to drop around case and screws on to male threaded shell holder base).

Slower buts saves cases.

You probably will not have to thin the rims

Last edited by Parabola; 09/17/21 04:39 AM. Reason: Typo