I currently carry a Puma .454 Casull while camping, canoeing, etc., for bear defense.
However, as most people say you'll be "lucky" to get one shot away, I've been thinking of either a single shot Ruger .458 Lott or maybe a Handi-Rifle .500 S&W. The Ruger is half the price of a bolt .458 Lott, and the Handi-Rifle is only around $300. I've seen a video of a bear shot with a .458 Lott and it dropped dead right now.
So would anyone consider a single shot super big bore for bear defense? Yes, you have to hit it, but if realistically you only get one good shot, is a repeater in a smaller calibre any better?