headspace or what???

[jglenn]

if you had a bad chamber EVERY round would exhibit the bulge to some extent...and it would also be in the same relative location( if you marked the cases and indexed them into the chamber).

 

[loadnplenty]

Ok so I got off the phone with ER SHAW just a little while ago. It turns out it is the BRASS. I did what they told me and measured the brass. And as they suspected the VIRGIN NEW BRASS was actually under SAMI spec. they said just continue to neck size and everything will look normal in another firing session. He also stated had I loaded bullets into the brass when I fire formed for the first time, I probably would not have noticed this bulge as everything would have strectched or flow more uniformly under preasure.