No...
If you can afford to go to Africa, get a REAL gun. The owner of this place went to Africa with a .50 Alaskan. MUCH better then a 45-70. He had cape buffalo problems, I think would have been solved with a REAL dangerous game rifle...The 4570 just doesn't work real well in Africa.
I will say the guy that recently took the big 5 with one had more charges then most guys do in 100 trips to Africa, and, he wrote about them...
Heck, Phil Shoemaker SWEARS by the 458 Win Mag, and, he's only hunting brown bear in Alaska...
There is a serious, and very real difference between hitting an animal bigger then most cars with a 458, or Lott, at over 2150 fps, and a 45-70. It's been written about, described, filmed, over and over. It's real, and huge.
On the other hand, you'd probably be better off with a 375
H*H you can shoot accurately then any of the above, you can't...
By the way, try calling a guide, and asking him about taking the 45-70, and, what it's approved of, depending on where you are going...