As a African I thought of adding my few cents to the discussion.

The marginality of any caliber on big game lies with the nut behind the rifle. Following up on poached game in the Low-veld of South Africa, it is astonishing to note how many rhino, elephant and buffalo succumb to a single shot with something as humble as a 303BR or even 7.62x39!

I do accept that it would be foolish to try imitating these facts just for the hell of it, and if you do you're a better man than I am, but it can be done, and has been done many countless thousands of times over. Now for the great question: is a 347gr bullet out of a 10.75x68 not better equipped to reliably kill an elephant than a 286gr bullet of the same construction out of a 9.3x62? Please remember that the 9.3x62 was near the top of the big game calibres before the .375H&H came to be. Can you rely on a 585Njati to stop what is trying its best to bite or scratch you when the chips are down, or are you better off with a light rifle that you can wield in a sure and confidant manner to save your hide?

A few thoughts on the matter...
Groetnis