probably cape buffulo
I'm regularly amazed at the somewhat religious following some of these 45/70 people seem to get into. It's as if when you buy one all your common sense and logic magically leaves your brain. This is fact and you can either come out of the trance your in and buy it, or reamain ostrich like with your head in the sand. The 45/70 is not a dangerous game rifle and does not have the needed power to be used on the bigger game in Africa in any kind of hunt other then a novelty or stunt.
One last comment don't think for a second that a 45/70 that kills an American Bison would make it good for cape buffalo. The two animals are not in the same league where danger, and the will to live are concerned. comparing a Bison and a cape buffalo is about like comparing a 45/70 to a 416 rigby!
Just FYI....the garrett ammo outpenetrates the .458 Win Mag. I doubt anybody would call that "a little light for cape buffalo". Pushing hardcast lead slugs of 500 grains or more at respectable velocities will def get the job done IMO.