That's right, but two cartridges are standardized nowadays according to CIP Homologation; the 500 Jeffery and the 12,7x70 Schüler.

I would be able to load both in my rifle, but if you have a new rifle caliber 500 jeffery you cannot load cartridges 12,7x70 Schüler. Years ago, Kynamco Limited and Norma temporarily no longer made the same cartridges. In the meantime everything seems to be standardized.

I hope that @Ithaca375 has a new reamer.