Writing for magazines, calibres matched to game animals ...

Nothing can be hunted with a .22 centrefire, though some of the small antelope would be fun to hunt with them.

.300 Magnums are the standard for all thin skinned antelope. Can't be killed with a .243, .270, 7x57, .308 or .30-06.

Wildebeest is pound for pound as tough as buffalo, so a .375 is needed ...

Eland, obviously a .375 ... at least I was told this by a PH before hunting mine with a .30-06 ...

Buffalo, you'll be under gunned with black death if you carry a .400, .416, .404 so only experts should try it with these marginal calibres. Even a .458 Win Mag is taking your life in your hands ...

Elephant, the .500's for all serious stories ...

Ha ha, only joking.

I plan to use my 8x68S on most plains game in the future, or the .375 or the .404, but have used the .30-06 in the past. And a .375 when that was all I took.

For most smaller and medium antelope I reckon a 6.5 would be great, whether 54mm, 65mm or 68mm,.

Doesn't really answer the question, but the question is too broad.