I was correct in my previous post. I'm using 38gn of Varget.
I tried some experiments.
1) I took one of my once fired cases and I seated the bullte to the same depth as some Hornady BTHP I bought
The result was the same. It would chamber but the bolt was hard to unlock and pull back and there was a mark near the base of the bullet.
2) I took a brand new case. Full length resized it (everything I've read says to resize new brass) and seated the bullet to the same depth as the Hornady.
3) I took a brand new case. Full length resized it and seated the bullet to the length my OAL gauge says (-.008).
No problems at all
4) I took one of the once fired cases and full length resized it. I seated the bullet to the OAL setting (-.008).
No problems at all (I then proceeded to do 3 more the same wan and had no problems)
5) Using a case gauge I checked a) the new case, b) the once fired case full length resized, and c) the once fired case neck sized.
They all were to spec
I am now at a loss. Any thoughts?