I agree with Colorado Luckydog for the most part. You're probably not going to carry a rifle around 24/7, and protection is useless if its not accessible. So, I'd probably opt for the bear spray first -- something you can keep in a handy pocket. Alternatively, some kind of pistol would do. While a 44 mag or 357 would be fine, I'd probably chose one of the bigger automatics, like a Glock 10mm, 45 or 40 S&W (or even a 9, it's only a black bear). They will give you more shots at a higher rate of fire, which, if your being charged and shooting all over the place, would be a good thing.

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I also agree that you'll probably never have anything like this happen again.