So I have some LC brass I got from brass bombers years ago as well as some from police rangers. Today I am sizing a piece of LC 07 which I am pretty sure has 5-6 firings on it and I can see the ring around the case web. I set it aside and getting the picks out tomorrow to see if I can feel it starting to separate. Now, I find LC 15 and begin to size it and the press locks up. I am looking at the piece of brass and there appears to be a bulge in the middle. I push a little harder and the bulge and now a ring moves lower toward the rim. I push harder and eventually the bulge breaks free and it and the ring move about 1/8 the way up the case. The cases fall in and out of the Lyman case gauge just fine but I am not taking a chance on them. I had one last piece size just fine. Any idea what causes this?