This topic seems to come up a lot. It is interesting to hear the responses.
Dotman,
I am really interested in the minimum caliber studies you reference. I would like to read them and go through the methodology, etc., as it seems like it would be hard to study.
I know that Tom Smith of BYU did a historical review that showed bear spray was effective in 92 percent of bear spray deployments, while firearms deployments were effective in 67 percent of cases. His standard for "effective" was the human left the encounter uninjured.
I am kind of a gun nut, and like to carry a pistol in the backcountry, but I always have bear spray (UDAP is the good stuff, IMO). I have the FHF Gear holster, which is awesome.
As far as .45 not being enough, or .40, or 9mm, or whatever. I think bullet construction and shot placement is much more critical. A hardcast .40 or 9mm in the right spot is going to shut down the nervous system right away. I agree with Ryan that shooting under stress goes a lot better with a gun you are more comfortable with.
I don't agree with Ryan saying bear spray being useless on a bear coming in your tent. I actually think it would work well. the downside is it would work pretty well on yourself, too.
My personal experience with grizzly bears is that they usually turn tail and run. I did have one aggressive situation with a young male near Hebgen Lake, but it turned out fine.