I don't think that Safariman was trying to hit the bear in the hips, nor was he saying that he is not a good enough rifleman--rather simply that the bear moved when he was shooting, so he hit it too far back.

My only observation is that a hip shot on a black bear could be made with most rifle using good bullets, and as such I disagree with the premise that a big magnum saved the day.

I think the saving grace was that he did hit the hips and broke the bear down, so that it couldn't get away with a lung shot only. I actually wonder how the story would have ended if the shot happened as originally planned, with the bullet angling up through the lungs from a steep raking angle. I could see that being a real rodeo.