This may be something to consider. I was experiencing bullet setback in 9mm. Then I experienced key holing from over crimping. This happened with three different brands of bullets. I removed the sizing funnel die from my powder measure spun it in a lathe with 600 grit paper for a few seconds. Then followed up with some semichrome polish and a clean rag. Reset my crimp die and both problems were solved. I am assuming that all cases are not equal in thickness especially after several reloads. I probably only removed 1 or 2 tenths of a thousandth, but that was all it took. A drill would probably work for this also, rather than a lathe. By the way this is my first post after joining a few years ago, hope it helps.
