Custom Gauge Pin

Measures neck inside diameter

Checking your Case Neck with Gage Pins:

After expanding use the corresponding gage pins to confirm the neck sized as expected.  The feel you are looking for is a light drag on the gage pin.  When sized properly the gage pin will act as a piston as you push the pin into the case neck while holding your finger or thumb over the primer pocket.  You can actually feel the air compress inside the case.  Quite often the brass can be harder or softer than expected. By stepping up or down on the expand mandrel bullet tension size you can achieve the desired neck tension to your gage pin.