Skylark: get a set of the LEE Precision dies for the 8x50R French Lebel. Back off the sizing die and run your x56R cases into it: come out ready for .323 slugs.
Guys with original rifles in 8x50R can load for their oddballs with 7.62x54R brass, trim to length first, then use the Lebel dies to push the shoulder back to where it has to be. Sounds crude but it WORKS and that's all my 1917 Carbine cares about. If you are dealing with fired 7.62 cases, try them in your rifle first to see if they chamber (they should); if they don't, the FL size them with your 7.62 die with an 8mm expander installed.
A cartridge case is just a brass bottle to hold everything together.... and brass is pretty easy to push around if you are careful.
Hope this helps.