I don't know the full story here, but Harald Wolf mentions his efforts to standardise and re-introduce the .500 Jeffery in some of his Hatari Times articles.

I assume that if it is just some difference in chamber dimensions (not bullet diameter), then as long as you chamber your rifle for the largest you should be fine - you'll just end up fireforming brass if it happens to be slightly undersize!

Maybe that's too simplistic and I'm missing the full story...