Stolen off the web. Gage pins in collets has been going around for a cpl years. The original idea was custom made(collets),this is one utilizing a cam lock bullet puller. It's for setting tension/interference. Mostly a JB thing but posting to possibly jog some brain cells?
The BR guys have a better setup now than the bullet puller. Dedicated die with two-diameter pins, like a normal cast bullet expanding spud except they don't have a belling feature. They hydro press from 21st Century Reloading has been out for a while. I still prefer a spring scale on the press handle for measuring seating pressure of cast bullets.