Case on the bottom is the one that burped.
If you look closely you will see a slight swelling forward of the web. Case walls are ballpark .008" in thickness with very minor variance. Bullet heel diameter is .208"-.210" with a preponderance hovering at .210". It is entirely possible that a slight increase of case wall thickness with a corresponding smaller diameter heel would address this favorably, but that would be speculation on my part.
That is all for now.