Hey Guys, thought I'de weigh in.
I am a handgun hunter. I've been doing it for about ten years and have hunted both white tails and black bear with handguns from .357 to .454 Casul. I used to think that a .41 or .44 was a starting point for black bear but for the past few years I have only used my .357mag. The barrel length is the MAIN factor in penetration. My hunting revolvers are all 6-8 inch barrels except my .454 which has a 10 in barrel. I use VERY hot handloads with my .357 and find that 190 grain Hunter's Supply Hard Cast bullets work best.
http://www.midwayusa.com/viewProduct/?productNumber=2046141371
I have not yet had the need to take a second shot on a bear and the penetration and shock transfer from these bullets is superb. I have a Thonpson Center Encore pistol with a 10 in barrel in .357 but its a single shot, suitable for deer and gives me a little more range but there's no real difference in knock down between the 6in revolver. I know that there's a group consensus that black bear are hard to kill and that you need to be gunned to the teeth but it's just not so. I have used my .454 on a Bison hunt and killed a 954lb bull two years ago. There's no need for that kind of fire power to kill a +/-300 lb black bear at close range.
I am a biologist and have worked in areas with heavy bear/human conflict and have never needed more than bear spray. For all the people that think the spray is not effective, I'm sorry but some of you guys just don't understand the differences in bears physiology. A blast of bear spray will not only stop a bear but sometimes they will even be so incapacitated they cannot even stand for several minutes. I'm sorry to go against the grain here but as a handgun hunter I have direct experience with this topic.