I had a partial case head separation using a 1.8oz buffer

[DeNinny]

That’s a piece of brass that was ripped out of the chamber while it still had residual pressure on it, (but still didn’t exceed case length).

Has nothing to do with the feed cone or bolt face, and everything to do with early extraction from cyclic rate being ahead of the window.

We were wasting time looking in the wrong places.

I respectfully disagree. The other failure model is still viable and fully supported by the picture.

And I'm fine if we agree to disagree. It's been a great thread and I've personally learned a lot for my own reloading purposes myself.