I agree with SuperSneakySteve. A 158 gr. 357 caliber XTP bullet traveling at 1250 fps has about 550 ft. lbs of energy out of a 4" bbl. See Ballistics By The Inch:
http://www.ballisticsbytheinch.com/357mag.html
That is pretty good wallop for the black bear scenario the OP referred to.
I personally carry a 4" SP101 for back up when hunting. Nice shooting gun.