9,3x62 is a great chambering ... I have two. Love them.

If you want a rifle that will make the legal minimums for many countries in Africa you should consider the .375 Ruger, the .416 Taylor, the .416 AR, and the .458 AR for standard length Mauser actions. If the project can wait a little, the .416 Ruger may be defined and reamers available sometime in 2008. They will all work without requiring so much relief of the ramp that it weakens the action.

Getting magazines to feed will remain something best done by a good smith and may require new or heavily modified bottom metal. Being a cheap old retired guy with a few small tool like a mill, when I built the .458 AR (a shorten, necked up and improved .375 UltraMag case) I had to build a "windowed" magazine arrangement. Took a lot of time and gave me a "1 in the jug, 3 down" rifle. It was not easy though.

The .416s and .458s are significantly more rifle than are the .375s.