Hi mikemayberry, I think you are correct about your problem happening while seating the bullet. I would guess that you have your seating die turned down to where you are applying the crimp while seating the bullet. The small cases for .223 are too fragile to seat and crimp in one opperation. Every once in a while, the crimp will get a firm grip on the bullet before it is seated all the way, so the shoulder gets moved back, causing the bulge you describe. Turn the locking ring on your seating die down a turn or two. This will raise the die, so you are no longer crimping. turn the seating stem down to get your correct O.A.L., and the bulges should go away. If you want a crimp, you will have to turn your seating die back down to use the seating ring, but be sure to turn the seating stem up until it will not contact the bullet while crimping.