[CarbineCaleb]

I would also try to moving calmly but deliberately out of that line between momma and cubs to avoid problem, and if it charges, wait to see if it's a bluff charge, or if I can stop it verbally first, with gun in hand. Real good chance of that.

Once it gets 10 yards or so away, if it is still coming like a freight train, I'd get off a couple of shots and see if still coming, try to dodge the charge, matador style to allow another clean shot or two (if it is big and/or running flat out, won't be nimble)... would not let go of gun no matter what until it was empty. Shoot at throat, heart/lung, maybe even face if point blank... only take a headshot if have a hard cast bullet like the Buffalo Bore or Federal CastCore.

I think the average hunter would stand a good chance (say 90%+). I think an expert hunter would stand a 99%+ chance. But if it's a person who's unfamiliar with handguns who somehow is holding revolver, maybe 40% - many bear attacks are not fatal even with no gun.