I know exactly what happen because the same happen to me. The bullet seating die is set to low on the case. When the ram comes up you will feel more resistance than you should just before the completed stroke. You end up shoving the shoulder back causing a slight ring. I had slightly different length cases. I had set the die for one case where it worked great on that one round or a few rounds with the same lenght. Some were longer and took away the clearance the others had causing the ring or muffin shoulder I call it. I keep the seater backed out enough to accept the longest case. This is why the FCD. Those 223 cases crush easily. I only set the crimp die for a slight crimp. You don't need a heavy crimp. You should not crimp bullets with out a canalure you may distort them in doing so. The primer problem might have also been the cases were not fully resized. Make shure the case goes all the way inside the die. We all have done the same things one time or another.