Squaregrouper
Kragaphile
This is a very good idea. I'm going to try it on a few.I thnk the neck expander ball on a rifle case is lower than the neck size ring. It sizes the OD on the way down (w/ the ball inside the case already), and it sizes the neck ID w/ the ball on the way up.
Ohh SG, You could press them into your lyman case gauge w/ an Arbor press (or a simple vise.)
Atblis has a good idea too - do they chamber when you drop the slide on them? If its close enough, the slide will drive them home to size. Warning, if you try this and don't want to fire it, they might not come out easily. So don't test this part at home