Good question--what makes an animal "go all loose" when whacked with a bigger bore? It sure seems to me that the whomp'em factor is real. It takes more to do more on a bigger animal.
Now whether any of that actually reduces time to death is probably unsolved.
Having shot deer with a 223, they often don't even react at all, run a little ways, stand around, and then drop over dead after 10 seconds. They seem to die in the same 10 seconds if shot with a 30-06, but I'll sure know that they were hit in the meantime. Same 10 seconds for a 375, but they will simply be "all loose" and just standing there until they fall over. This all with lung shots or very light bones around the edges, not CNS or busted out vertebrae.
