45 raptor is the cast hammer we are missing. In a semi carbine configuration they aren't unwieldy. My wife uses one in 308.
The weight is what helps keep it steady. I do worse with lightweight rifles offhand vs ones that may be a scootch heavier than I'd like. It also soaks up recoil better than anything.
On the 308, great, we have a baseline. I think that is impressive that the bullets failed & STILL KILLED IT. It's one of the reasons I really like splodies for broadsides, it doesn't fail to kill rapidly ime.
I have zero idea how hard those were pushed but, do know hornady is all about velocity, for drop on that match stuff. I would say give those another shot, but work a load down. If they blow up to fast, slow them down. If they blow up to late, speed them up. It's really that simple. Unless we get in to something crazy it plain works for broadside culling.
If you swage your own you can change things(jacket material/thickness, bonding, inner alloy, ect.) to make your perfect bullet. Fiver could expand on that.
I wouldn't expect expensive African game bullets to perform much better in the way of instant killing. I would expect them to cost alot, expand reliable, but maybe not increase the quickness of the kill. That takes turning insides to mush, that takes explosions inside. Ymmv