Re: riddle me this ole wise one's
Reply #12 –
Early on you mentioned they chambered as usual.
Meaning not snug. In the past I have headspaced once in a while a hair on the tight side and was not able to size that tight(without shell holder mods). If the cases chambered tight, I ended up with hard bolt lifts (no place for the brass to grow). Being you started with new brass my guess that was not the case. But certainly worth accessing.
I have been guilty of using cases for head space gauges and don't advertise or recommend it. It works in combination with a little luck & common sense. Worst case is you can end up too tight. You probably used a go-gauge which is correct. Of coarse a tight go gauge or worse yet out of spec one could get you there also. Long story short your new & sized brass should fit "loose" in your chamber.
No smiley evident and all load data below max makes me think it is not pressure. But rather a brass issue as you originally thought. Did you compare the case head to shoulder dimensions of new brass, Hornady fired, sized Nosler and fired nosler?
I believe a 9mm or 10mm 3/8 drive socket placed over the necks will serve as a fixed datum for measuring shoulder to case head. The number you come up with on overall will let you compare the lengths within .001. I use this method all the time for setting bump and it's almost foolproof. You might have a fancier tool but those measurements might help in solving the problem.