Where I live, the only question is: Will it reliably take down an Alaskan coastal brownie with one shot? If not, you need something bigger. I consider a .308 the minimum, prefer a .30-’06 and, truth be told, a 12 gage pump would be a better, more versatile survival weapon. If I lived in the lower 48, I would choose an AR15 in .223 (For ammo availability) since the biggest thing you would be likely to shoot would be a human and they tend to run in packs.
I’ve read that those who live in Grizzly country would choose the Winchester Model 71 in .348win if they could only carry one weapon. Unfortunately since these became collector items the ammunition is no longer manufactured by Winchester.
If I lived in areas with Brown bears or Grizzlies, I would never go in the woods without at least a Ruger Super Blackhawk loaded with hard cast Keith style 240 grain bullets.
I would probably try out an S&W 460 just to see if I could handle it. You are probably right about a pump loaded with slugs.
I saw a Black bear just a few days ago near my house. He was a big one too. For some reason they don’t worry me too much but maybe they should. I have read that Black bears kill way more people than Brown bear or their cousin, Grizzlies.
I think if it were a shotgun, I would have a slug in the chamber then 00 3 inch buck for the rest.