A between the shoulder blades shot would be very unlikely on any animal of that size unless it was laying on it's belly, maybe in a trap or snare, not moving. A .22 short ( or long rifle for that matter) will not break a grizzly's spine, even if the muzzle was held against it. A .357 mag with 158 gr jfp will not break a moose's neck at 20 paces ( proven personally). It's a good story, kind of like oral history, and we all know some people that can tell some good ones. It may be that if the event really did occur that a few details were left out, such as a previous shot or shots with a more powerful rifle, whether the bear was still alive when assaulted with this magical .22 short, maybe this was a cub? I don't for one minute believe that anyone successfully killed an adult polar bear, grizzly, or even black bear with a .22 short in the hump. The best you could do would be to p-$$ him off. But of course, none of this has anything to do with the original post requesting feedback as to the best bullet to use in a 45/70 for a grizzly hunt, it seems to have morphed into a general discussion about bear hunting, mostly by people who never have and probably never will hunt the big bears.