IF you cannot stop thebear with a rifle, you are in deep kimche if you start shooting at him with a handgun! That is, unlless the wounded bear has run you up a tree, in which case having a .44 Magnum or .454 Casull up there with youmight permit you to shell him as he ascendsup to your perch to bite you!. A .357 will work, I have seen this done. But a bigger caliber is better insurance, and NEVER shoot a handgun at an unwounded bear if you can in any way avoid doing so. If you MUST shoot to prevent injury, by all means shoot the advancing bear right on the tip of the nose, so the bullet can travel up his nasal passages and into the brain, killing him instantly. MAKE SURE YOU DON'T SHOOT TOO HIGH!! A high shot can strike the sloping skull, and go right up over his back!

As a person who hunted bear of various descriptions for three years in Alaska, I have very little faithin the concept of using any handgun on bear if a rifle or 12-GA slug shoitgun is availbable.