I'll throw my .02 cents in
I have only hunted Africa once, (But am going back in 2010 with my sons).
I shot nearly everything on my safari with my old Remington 700 in .338 WM because my CZ .416 Rigby wasn't cycling correctly. I use 250 gr Nosler Partitions.
My wife made a comment at the sundown fire that she wondered if my .338 was enougth gun for my dangerous animal. Charl Watts, one of the owners of Steyn Caracal Safaris, replied that he'd have no hesitation shooting an elephant with the right bullets with a .338 WM. That to me, is testimony enough.
I did finally shoot my blesbok with the .416 Rigby. Straight on in the chest. OMG! It went from stem to stern. Entrance hole that you could put your thumb through. When we went to pose him for the photos, you could have tied the frond legs behind it's neck.