I think I’m starting to see why we’re on different planets here. Are you assuming he was shooting for the spine? You’ve made mention of the size of a vertebrae and that the spine and neck being smaller the cone of fire. You also mentioned hitting the spine at that distance was lucky.
I guess I was assuming (that’s really all any of us can do since we have no details on the shot other than range) that the shot would be more towards the shoulder but this would still be in the cone of fire. If I had that shot and had to take it, I would be aiming right at that red dot in the middle, with a high confidence that anything inside the circle (which the OP’s shot landed in) would have a very high likelihood of resulting in a dead elk very quickly. Even Avery said “I would have aimed just inside the point of the shoulder. But at that angle, it’s game over for that bull.
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So I guess I don’t look at it like a lucky spine shot. I look at it like it was towards the outside of the expected cone of fire, and still resulted in a dead elk very quickly.