RS,
I've used a .30-06 and a .270 on plains game in Africa, but haven't used a 7x57 although I wouldn't hesitate to do so. My loads for Tanzania for my .30-06 were H4350 (I've forgotten the exact load) pushing a 165 grain TSX. The largest animal I took using that combination was a stud zebra. It worked very well on everything I shot with it. I used the same rifle on a trip to Namibia, but loaded with 180 grain Norma Oryx bullets and again, H4350. Since no dangerous game animals were on the menu for that trip, the .30-06 was the only rifle I took. The largest animal I shot with that combo was a big eland. I used a custom .270 on a trip to Zimbabwe. My load was 59.5 grains of H4831 pushing a Bitterroot 130 grain bullet at 3100 fps. Performance was just fine. As someone already alluded to, Eleanor O'Connor shot just about all her African animals with a 7x57 except her elephant and perhaps a lion or two. For her elephant, she use her "big rifle," a Brownell Model 70 custom made for her for a tiger hunting trip to India. It was a .30-06.
