A 500 Nitro double and a 375 H&H is about perfect for Africa. After all 2 rifles is about the limit for most countries.

So I would get a 300 Mag. A 300 mag and a 375 would make a great pair for North America.

A 3 rifle battery of a 300 Mag, a 375 H&H and a 500 Nitro will cover all Big game hunting.