I've never shot a bear although I have encountered one that ran from me while hiking. So I can't say what it takes to effectively stop a bear. I do know that a .357 doesn't always stop a determined man immediately and a fataly wounded man can cause you a lot of damage before he expires. I also believe that a bear is tougher than a man.
So...
If I couldn't hit the vital area of a bear with a gun bigger than a .357, I would practice until I could.


He who joyfully marches in rank and file has already earned my contempt. He has been given a large brain by mistake, since for him the spinal cord would suffice.

- Albert Einstein