Just an update on some further info. 21 Century has supplied, & perhaps something to take note off if considering this unit.
21 Century Shooting allowable tolerance is +/- 0.0005 for this gauge. So if you are trying to assess if you are within 0.002 concentricity (accepted benchmark) there is a potential 25% error reading with this concentricity gauge unit. Add to that the Mitutoyo Test Indicator has a 0.0002 accuracy repeatability error, that all adds up. We are measuring very small tolerance’s here. Hope I got my maths (25%) & theory correct here.
I will add that 21 Century is being very responsive in trying to resolve this issue. As indicated earlier, one of the roller bearing(s) (case shoulder support unit) is not so free flowing which may be contributing to the variation here.
marksman, what is the Concentricity Support unit & test indicator you use to take your measurements? I’m sure readers would be interested in that information