Hi John,
I play with a Vetterli.
I converted mine to centerfire and it is not to difficult at all.
I form cases from 8mm Lebel brass using a cutoff die I made for my reloading press and a jewlers saw.
I then run the shortened case int my Lee sizing die far enough so it just chambers.
Fire form them and then trim to final length.
Mine has an excelent bore that measures .429" diameter.
I use the Lee 325 grain mould meant for the 44 magnum to cast bullets.
Pan lubed without gas check they will easily shoot into a 3", 5 shot group at 100 yards.
Check out swissrifles.com forum for a very in depth look into Vetterlis and all other Swiss rifles.