I second a 4 in 44 mag or 45 Colt. Much easier to carry than a longer barrel. I carry a m57 4 inch or 657 mt gun in 41 mag. I live in Bristol Bay area of Alaska, serious brown bear country. Guess I got on the 41 kick back when Dirty Harry and the Pipeline drove 44 mag prices insane.
But the 44 is so much more available and in greater variety.
I carry cast 265 loads by Corbon, Buffalo or Alaska Backpacker, or home loads. Also 250 gr Corbon or Federal stuff.
I carry the gun in an Alaska Sportsman's Chest Holster and have been very happy with it except for the steel snap clip than can scrape up wood on a nice long gun. Also wish there was a better alternative to the plastic clip on the retaining strap. Can be hard to release in a tight situation. But it stays clipped and I don't worry about losing the gun when I'm bushwacking thru thick alders ( imagine continuous limbo or crawling almost on hands and knees). The gun stays close to my chest and doesn't hang up on brush like a hip holster. Reasonably light wt and moderate price.
http://www.alaskasportsmanproducts.com/Another choice made in Alaska and popular with many is the holster made by Simply Rugged but I haven't used one: The Chesty Puller Conversion System:
http://www.simplyrugged.com/store/index.html Haven't had experience with bears real close and muzzle blast - happily. But at moderate ranges they often don't react at all to gun shots. I have fired at the feet and over the heads of several brown bears at 30 yds to 60+ yds and most cases the bears ignore it or don't seem to know what is going on (300 win mag or 41 mag). Even shooting the water in front of a bear and making quite splash had little effect on one last year. He only reacted when I nearly hit him in the nose with a rock and I wonder if it was that he smelled my scent on the rock. He ran off but I was about ready to heave another rock that I had first rubbed in my pits. I'd been out on a float trip for several hot days and was getting pretty stinky.
HTH