I can't believe we are 20 posts into a thread about bear defense, and no one has yet called you an idiot (or worse) for wanting to be prepared. I don't know what this board is coming to. The bear whisperers must all be on vacation. I am leaving this weekend for a week long camping trip out in the Rockies, and I will certainly have my 44 mag handy.
You have been given good advice about ammo selection for 357 mag. You want the heaviest, fastest, hardest load you can find. I thought I was going to take a 357 with me, because the front sight of my Ruger Blackhawk blew off while shooting about 2 weeks ago. I sent it off to Ruger, and they have installed a new sight on it much faster than I thought they would... so its back in commision.