See this thread
Bear Guns first.
You will want the heaviest bullet you can find such as a 300 grain Barnes. I'm sure others here can recommend makers of heavy hardcast bullets. Once you decide on the bullet, go to the the bullet manufacturer's load data and slowly work up to the hottest loading. There are some loads which are designed for Rugers and T/C Contenders only. These loads are too long to fit your 629's cylinder.
That being said, just yesterday I saw a show on H2 about monster bears. They told a story of a guy that fired his .44 in the air to scare off a grizzly. The bear kept at him, he holstered the .44 and planted a rifle shot in the bear. The bear got up, the rifle jammed, and before the fellow could get his .44 out again the bear was on him. He survived, but was severely mauled.