I'm assuming that since you're writing from NY, you're talking about black bears and not BEARS as I know them. I agree with tg. If you put the right size ball in the right place on a black bear, game over. If you put the wrong ball in the wrong place, you simply aren't going to have time to go for your backup. Bears are FAST and that sucker is going to be headed into the next county before the smoke clears. Might do so even with a good hit, but either way you have plenty of time for a reload.
If you're talking BEARS, the right backup is nothing less than a 375 H&H in a pair of cool hands standing right beside you. If the bear doesn't drop instantly at your shot, immediately start poking .375 diameter holes in the hide and don't stop till the last part stops moving. If it gets out of sight, both of you reload, say your prayers and work together to follow it up. The case is open on who is hunting who at that point.