Ian, I don't doubt that the 44 will kill a bear. But you are not talking about stopping a charging bear. Just like Mr Bell shot a lot of elephants with small bore rifles he picked his shots. And a lot of men got killed trying to do what he did. Light rifles or hand guns like the .44 are
Take a decent shot at a bear it(44) should do the job given enough time. Better yet if you have a second shooter as backup if it goes square. But to stop a charging bear it is a choice of desperation. I would have used a .22 , a bow, or a big rock. I was desperate and dumb to have gotten into my situation. I had a far greater chance of wounding my bear and either loosing him or having to track a wounded bear assuming he did not kill me. Even with my friend and his much larger bore rifle I'd rather not need to track a mad, hurt and desperate bear.
I have seen several stories of big game taken with small bore or pistols and can only say that's your choice. I am also sure the many stories of lost game never get published.