Jim and Cosmoline,
I don't doubt the stories, but I have to wonder if there isn't something more to them. In the first case, I suspect two balls; twice the bullet weight would definitely get one's attention in the recoil department. As the "shot it out" tale, again is that the whole story? How does one shoot out a stuck ball in a muzzle loader? The little amount of powder that could be dribbled in the nipple hole or the cleanout hole would not be an overcharge and I have never had anything happen when I have "shot" a load out that way. I suspect there was already a full charge and a ball in the barrel when the brother decided to load another ball and got it stuck. Firing the gun would almost certainly bulge the barrel.
Jim