I think you would have to lay down and wait until the bear is over you and shoot up through the gap in the bottom jaw into it's brain.
Otherwise, the noise and stinging might discourage it.
We were out Sunday and I shot a few others handguns. A Ruger P-Series in .45ACP and a H&K USP in .45ACP and a Glock in .40S&W. All of them were thicker than I would like for CCW. Especailly the USP. I'll stick with getting my 1911.