I'm going to suggest a few things: you're from idaho, so your bears are know for being on the heavy side, and last I knew you had more than curious bruins to worry about....the smallest piece I'd be packing would be a .44mag in a Double action revolver. The .45acp would likely work alright, however, when a bear's laying on your chest, there's a LOT of things that can happen that will cause an auto to jam...a DA revolver makes things easier, you shouldn't even consider a SA IMHO, as much as I love them, they're just not suited for close quarters "combat".

A .454Cassul or .480Ruger Ruger Super Redhawk would make great choices, while the .44mag Redhawk wouldn't hurt you either.

One thing I'm noticing being suggested is "HEAVY LOADS", which isn't necessarily a great idea. At the range you'll be using this gun, standard .44mag loads are going to make big dents in the bear, while heavy loads might do better, you'll also not be able to shoot them as quickly nor accurately most likely. I'd rather have a gun that puts dents pretty close together and gets them there fast than have a gun that makes a HUGE dent, then points at the sky.