300 blackout woes

[popper]

1 out of maybe 10 doesn’t fit….completely random. In what way? Bad HS, neck too big, shoulder in wrong place? Wilson or Sheridan? My understanding is the Sheridan is cut to min. SAAMI specs.

[Hannibal]

To make certain that the neck diameter is indeed where the problem lies in the rounds that won't chamber take a fresh blue of black magic marker and cover the entire case with a nice, even coat of ink. Let it dry well and then check it in your case gauge. Probably should do 2 or 3 to be certain it's the same problem every time. Then let us know what you see. That will determine what needs to be addressed/corrected.

[Chainsaw.]

Well one thing I have figured out with the case gauge is that I dont have one issue, but two. The most prominent issue is in my brass being all range pick ups. Many of the cases (20%?) have some sort of rim scoring. Some have a hard extractor mark that is pulling the lip of the rim out leaving it to get hung up, a few have a much smaller protrusion off the rim, but enough to hang up. Fixing/elimination of those cases is resulting in only a few of the cases being problematic. Those remaining ones are neck size issue, for the time being Ill just eliminate those cases entirely.