I’m a former backcountry ranger at Rocky Mountain NP and Mesa Verde NP, and on the bear management team at both. Our duty weapon in the early 1990s was a S&W 686, 4” .357mag. We carried the old Black Talon rounds. In 1995 we switched to Sig and we were issued P229 in 9mm or, if we purchased our own -which I did- we could carry P229 in .40, or P220 .45 acp. I chose the P220 with Black Talon rounds. A ranger buddy of mine worked in Alaska. When we had revolvers, Alaska rangers could choose .44 mag S&W and they carried 870 pump 12ga with slugs for the big bears. When we switched to Sig, he chose a P220 in .45. All said, I’m inclined to carry my .357. It’s been on my hip in mid, rain, snow, ice, on foot, horseback, ATV, and I never had a worry about a malfunction.
For black bears our orders were , in order: noise, pepper spray, cracker shot, and if none of those worked, 12 ga slug to dispatch the animal. Animal attacks are very rare, but when they happen, they typically happen without warning, so whatever you carry, it should be accessible. You know how the movies show a mountain lion growling to announce its attack? That never happens. In Colorado my concern was always lions. And most bear problems are caused by people who approach the animal too closely, or attempt to feed it-I’ve seen some people take crazy chances for a picture.