There was a thread on this a little while ago - here's the link
http://forums.nitroexpress.com/showflat.php?Cat=&Board=bigbores&Number=47004&page=1&view=collapsed&sb=5&o=&fpart=1

wolfgang Romey also load for the .500 Jeffery and GS Custom, Sabi Rifles & Ken Stewart also stock reloading componants for it.

If you need any really technical questions answered then Alf who posts here is the real fundi........