I know a guy in Sweden, who uses pretty much only a 458 wm loaded with 350, 400 and 450 gr barnes bullets. He has shot pretty much everything in Africa with it without much trouble. I will try to get you some better details.

I also have a 458 wm. Decided to by another rifle in 458 lott for my buffalo hunt in Tanzania last year. The Lott is easier to load in my opinion.

I think the 450 gr barnes would work well on buffalo. I would also think the 480 gr woodleighs would also work. For a little more range the 350 or 400 should work well for other game.