Interesting stuff. I've always shot the animals "just" behind the shoulder and all have dropped on the spot. A couple I've had to shoot in the neck as that was the only shot I had. They also dropped on the spot. Of course I've used a .300 Win Mag (150 gr powerpoint or corelock) on most of these animals. SIL and his nephew both shot their deer right behind the shoulder (using PB 245 Aerotip) and both dropped on the spot and they did get penetration through the whole animal. Both shot at about 50 yards. If I would have used a 180 gr bullet out of my .300 WM I don't think the results would be nearly as good.
I see animals shot on tv run long distances. My theory is they're using a bullet that penetrates through before expanding all the way and it's not expending all the energy in the animal. This is what I would NOT want and why I'm leary of using sabots at the lower velocities of a muzzleloader. A 12 gauge shotgun with a hunk of lead will drop a deer "right now" also and I think simulating that (PB Aerotip) is desireable. I don't like to track deer long distances. On our land they could reach the neighbors land and I'd lose it.