Oh please. you dont need a big gun to survive a bear attack!.......a .22 will do just fine. Just make sure you actually hit your target when you shoot your buddy in the knee, youll get away just fine :-) haha

In seriousness. I grew up in Alaska........i've seen angry bears. i wouldnt trust anything LESS than a .44 mag.

9mm will piss him off

.40 will piss him off more

.45 may not reach him.

.357 will just make a small small through and through.

.44 will slow him down.

.454 casul will really slow him down

.50 pistol will make him crawl

.500 mag will make him dig his own grave :-D