Gryphon, the 2mm shouldn't make any difference unless your magazine is already a tight fit for the 9.3x62, however the Mauser M12 has a barrel that is not removable, as in it is not threaded. Some other process has been used such as a shrink fit I believe but Mauser (Blaser) won't divulge that information. In other words re-cutting a chamber is not an option. The ADI manual as stated above gives load information that is very under-powered, and when I contacted them as to why that was the case, I received a really dumb answer that explained nothing. There is however plenty of re-loading data on the internet and the Nosler manual has data as well, so does Nick Harvey's book. Depending on your barrel length the 9.3x64 is good for about 250-300 fps over the 9.3x62 which makes it a worthwhile conversion. It is a super round with interesting history, don't let anybody tell you otherwise. If you want to do it than go for it.

Waidmannsheil.