Another thing that has bit me is having the bullet seating die set to low where it is “bulging” the shoulders out. Back the die out a bit and lower the seating plug to get the correct oal.
If this is what happened, you can pull the decapping pin out of the sizing die and run the loaded rounds up into the die slowly to push the shoulders back in. It depends how bulged they are, whether it will work or not.
This is where the body die or the trim die come in. They are very handy for fixing a bulged shoulder. But, it's better to trim everything as close to the same length and avoid it all.
kwg
