RE: Hunting with a .500 S&W
Its a combonation of things. Not just bullet, not just placement. When It comes to shooting a living animal, nothing is written in stone.
As for the BT's, I have used them and have had the opposite exp. as you described. I switched from them b/c they were leaving too big of an exit hole, damaging too much meat.
However, you can take a bad bullet and get good shot placement, such as the hear or lungs and the animal is done for.