I think the only handgun calibers I would even consider close to the task for protecting me from a bear would start with the 454 Casul Mag. and go up from there. Handguns simply are not up to the task.Here is a link to a thread on handgun rounds used to kill feral dogs. The main poster in this thread has been tasked to kill numerous feral dogs on a couple hundred acres of ranch land :http://www.10mmtalk.com/index.php?showtopic=3741
He is using mainly 40 S&W, 10mm Auto, and 45 ACP and good quality, factory JHP’s.
He states that most hits through the torso don’t even slow the dogs down. Often they don’t appear to be hit at first and usually run off and die after running a few dozen meters. About the only hits that drop them in place are those that hit and break the shoulder.
This thread shows bullets that he has recovered from these shots and explains how the subject reacted, where the round hit, and how far it penetrated. It is quite an eye opener on handgun performance for their lack of immediate stopping ability.
The onlypossibility I might try if given no other choice would be a round put through the bear's snout and up into the cranium. Trying to hit the cranium through the skull is a bad idea since the bone thickness and angle it is normally presented make it nearly impossible to punch through.
If this is all the performance he is getting out of handgun ammo on dogs I would not expect much of anything on wild bears. Pepper spray would be a much better idea.