I do a lot of camping in bear country. I’ve been to Bannf. Bear spray is more effective than a firearm at stopping a brown bear attack. Bears have super sensitive noses and eyes, bear spray is immediate pain.

Bears are extremely muscular from the front, so even if you could manage to shoot one several times from the front, you’d have to use non-expanding bullets like hard cast lead or full metal jacket, which aren’t as lethal as expanding bullets like flat nose or hollow points are (for people). Expanding bullets would be stopped by muscle in bears. Non-expanding bullets are slower at killing things (I believe it’s illegal to hunt with FMJ around me). Bears can run so quickly that a lethal shot killing a bear in two seconds might not be enough time to stop the bear before it could hurt you. And if a lethal shot took a minute to kill a bear, it’s not effective at stopping an attack.

9mm has stopped brown bear attacks plenty of times, but it’s risky. Both US Parks Service and Parks Canada say bear spray is more effective at stopping a bear than a firearm. I think Parks Canada still uses 0.303 rifles to rangers, but that might be for polar bear. Canada is really strict on pepper spray and mace, but you can purchase bear spray, even if you’re not a citizen. I don’t think a non-citizen would be able to hike with a holstered 10mm or .40SW pistol anyways.

Bannf was really crowded when I went there. It’s beautiful but the “must see” scenic spots are all filled with Instagrammers. Bears are probably less afraid of people, and I saw plenty of idiots 10 meters from a brown bear with an SLR camera without any precautions at all.

Pro tip: Jasper is very similar terrain, is also a Canadian Park, and is much less crowded. When I was there a couple of years ago, there was zero cell signal an hour before we arrived at the park. You’ll need paper maps or offline GPS. If you want wilderness with fewer people, try Jasper Park.