It looks like the shoulder is making contact inside the die, and the additional travel in the press ram is causing the bulge.
Back the die off, so it just sizes to within 0.010" of the base of the neck, and see what happens.
However... you didn't specifically say what type of die this is. Is it an actual neck-sizing die, or is it a full-length-sizing die that you're using for neck sizing?
That "bulge" looks like regular expansion (that has been partially re-sized), to me. And... it looks like your chamber may not be symmetrical. So, if you rechamber the case with a different orientation than it had when ejected, it will offer resistance (sometimes substantial).
__________________
Don't even try it. It's even worse than the internet would lead you to believe.
|