With enough practice you can take just about any game with just about any rifle (within reason, you couldn't take a elephant with a .22 short). I remember hearing about one ivory hunter (I'm not good with names, someone else might remember his name) who used to use a .243 for all his hunting. His gun bearer used to carry a .600NE double in case one charger but aparently it was never used. But that is an extreme really, I would say maybe something slightly bigger, Midnight is a big fan of the .338 Lapua mag, I would go with the 375H&H for an all around. But once again, why only own 1 rifle???

M82A1