looking to do a one rifle does it all for all N. America and Africa should I ever get there.
I would think it sort of depends on what game you intend to hunt in Africa (PG vs DG) and what country. As mentioned above, you really can't go wrong with a .375 H&H. It is the legal minimum caliber in several African countries for DG (including SA I believe), and it will certainly be effective on any PG you encounter. For North America you can always work-up some light loads. Hell, I talked to guy yesterday that uses his .416 Rigby for white tails and pigs (using light loads).
