BKDinTexas, everything you have hung around your middle gets heavy by the end of the day. Between the years as a soldier, in sunny southeast Asia and 30 years as a cop, It all started off with either nylon web, canvas, and some sort of very old WW II leather, and then steel service revolvers, and heavy leather duty belts. Weight does matter.
Your mountain revolver, and the 329PD probably would not have much difference in firing time, if a bear had you in its crosshairs. Would you be able to stop it with either? I personally doubt it, unless you were extremely lucky. I suppose its better than a frying pan, or a fly rod. Or, any lesser caliber, for that matter.
If you have time to see the attack or ambush forming, you have the chance to extracate yourself from it. If you don't see it, or preceive it, whatever you are using is going to be contact shots, up close and personal. Its not going to matter if its an 8 3/8" .500 S&W., or an American Derringer in .45-70. It will be close, it will be messy, and you are going to get hurt.
From what I am led to believe by people that have actually experienced a bear attack, the initial attack is about once removed from being hit by a truck. Except the bear stops on top of you and starts tearing away parts.