I read "Bear Attacks of the Century - True Stories of Courage and Survival" by Larry Mueller and Marguerite Reiss (the book S&W packs with the 500 S&W Survival Pack). This book recommends that you only carry a double-action pistol of major power when in bear country. In many of the attacks covered, the victims did not know of the bear's presence until it was on them - it could be difficult to cock a single-action when you are being shaken like a rag-doll without loosing the gun, but you might be able to simply pull the trigger.
As I wrote earlier in this thread, I participated in a bear-attack rescue in 1960 and a week later killed a grizzly that had treed me. I used a Ruger Flat-top Blackhawk SA and remember having some difficulty cocking it while hanging onto the tree and being shaken.
No fun and I never go into bear country (black or griz) unarmed
