I think whatever you have is fine, get some hot house ammo and make sure it shoots.
This is both the bullets you need and a great explanation of shooting bears.
I’m gonna get a glock 20. 10,000 ft/lb of hate in one magazine. I can put a light on it too in the event bears come into camp at night.
Bears aren’t bullet proof and won’t know the difference between calibers, you only have 2 seconds and 2-3 shots after the bear charges, it’ll be a head on shot and most people shoot an auto faster and much better than a revolver.
Either You kill him outright with a cns shot or You penetrate to the heart and Lungs and he has time to maul you before dying like DeCaprio in “The Revenant.”