I think maybe the real question should be: Can ANY pistol handle grizzlies, polar bears, or moose? I'm not talking about sitting in a stand over a bait with a .454 at 40 yards. In any situation, one of the above animals charging you at short distance (20-30 yards) will more than likely end with you being mauled at the least. They are just too fast in an unexpected encounter.
In an unexpected, surprise encounter where they are attacking, a 12 gauge or even a .416 Rigby probably isn't going to do you any good either. Unless you are ready, and prepared to shoot at every second you are probably a McHappy meal. The minute you sling the rifle or shotgun, reaction time comes into play
If you do have time to prepare, or the attack is not unexpected, then it a whole different story. Will an antique stop them? I don't know. Depends on too many factors that you can't calculate: distance, shot placement, what caliber/bullet. I'm pretty sure that IF you can put a .455 Webley round into their eye or ear at 3 feet that you've got a decent chance of stopping them. You just have to get them to stand still while you're doing it.