This is second hand, but a local chap tried them on elk and didn't get as long a shot as he thought he would. The elk was only 150 yards away and the bullet, which did not hit a rib going in, blew up in the lungs and didn't make it to the ribs on the far side. The elk died, but had he hit a leg bone or maybe even a rib going in, it may have blown right there and only wounded the elk.

Perhaps bullets that are designed for long range expansion cannot be trusted to perform properly at close range.

Perhaps it is better to use a good, known bullet for the game in question and not play with possible problems - Africa is a long way away to find your bullets are too soft for 99.8% of your shooting. I've never been there, just saying.