I've only been once shaky, but I used a 300 win mag. for plains game. It was plenty for up to the kudu, but I think a larger frontal diameter would be better for gemsbok and of course the required big diameters for dangerous stuff. I think my handy 25-06 would have done fine for everything else I took a poke at.
depends really what and where you hunt--JJHack may be able to give us some more info---but basically it's a 375H&H minimum for the Dangerous Game and for plains game you pretty much bring what you want--although I think the .30 calibers and above are the norm----chris
My step-father and I hunted in Zimbabwe years ago and we took a .338 and a .375. The .338 was plenty for all of the plains game we took. Quite overkill on lots of the smaller antelope. The PH with whom we hunted told us the many of his clients would bring a 7mm Mag of some flavor and a .375 and they'd be fine. If you're only after plains game up to and including eland, I would think a two gun battery of a .270/.280/30-06 and a .338 would be just fine....
I was there as an observer with my step-father in '84. He took a .338 and a .375H&H. We took only plains game up to and including eland with the exception of a hippo. In retrospect, if you eliminate the hippo which we weren't planning on anyway, a .270 and a .300 Weatherby would've l;ikely been plenty.
Watching the small antelope absorb the energy of a .338 was interesting though... tough little buggers!