The absolute best thing to use is your guns barrel ... just because a case fits some " Case Gauge"
that doesn't realy mean anything ... it just means that round will fit that case gauge ...
Your "gauge " will take some unsized ones ... that's not very encouraging at all ...
Take my advice , before you load up a quantity of ammo ... gauge the round in your pistols barrel .
Just because it fits a gauge , that doesn't mean it will fit your gun's chamber and throat dimensions . .
I wouldn't put all my trust in a "gauge " others have ... and had to buy another accessory ...
A Bullet Puller ! Don't do that ...
Gary