Vance,
I tend to agree with the double actions. You probably won't ever bring this gun into play under the circumstances you buy it for, but if you do, more than likely it will be very quick. I love the single actions, especially the Ruger Bisleys, they are a delight to shoot and carry, but a missplaced thumb and you are a spectator. The S&W mountain is a wonderful firearm, no doubt about it, but I just cannot bring myself to buy a new one because of S&W's policies. The Ruger Redhawk or Super Redhawk is a high quality double action that has no peers. It is a little bulky and heavy, but still carries well in a good holster. If it were me, given you live in Montana (or that is where you will using it), I'd go with a 45 Long Colt with heavy loads. If you ever decide to up the ante, several gunsmiths can convert it to one of Linebaugh chamberings or the Casull. I'm not sure how big ol' Groaner grows in your neck of the woods, but the purpose of these types of guns is to stop the bear (not necessarily an instantaneous kill). You need to break bone and stop the charge. A heart/lung shot still leaves an awful lot of fight in a bear. Above all, STOP the charge. If that kills the bear - fine, if it doesn't, kill it with the second or third shot, the first shot is a stopper. To break bone on a big bear takes heavy bullets, the heavier the better in my opinion. Several companies offer heavy bullet loads in the 44 mag and 45 LC, usually with the LC having the most potential. Either the 44 or 45 will suffice, but I would personally go with the 45LC.
Having said that, I do a lot of work in remote areas of coastal Alaska and while in high brown bear concentrated areas, I carry a short barreled 12 gauge shotgun. I do carry a handgun when fishing or at times when the 12 gauge would, in all likelihood find itself leaned against a tree and me being out of reach, but I do feel more comfortable when I have the 12 gauge.