Can a 357 stop a bear? Sure, but so can a sharp stick if the stars align right. I'm of the opinion that you can't carry enough gun, but then again, I'm just paranoid that way.
After seeing a medium size griz absorb 12 rounds from a combo of 375H
H and 416 Rem, they earned my respect. I've also seen em fall over dead very quickly from one shot from an 06 though.