10mm has slightly thicker case so it is possible to swage the bullet and reduce neck tension in the process. I measured it with my FCD. Also Lee's basically instructions for the FCD lead to too much crimp. So you do have that as a possibility. Especially if you did the "add a complete turn" thing.
Yes, I post using a phone so my spelling sucks.
Converting Hornady owners to Dillon
one owner at a time.