The first thing I would do, and I've done it before, is seat a bullet at the lands and the case base on the bolt breach, and fire it using a mid size load. If that case then chambers in the rifle, neck size it, reload it with its normal charge & jump, and fire it again. For all practical purposes You now have a chamber cast of Your rifle. Don't worry about spring back, this is close enough for what You want to know. The only gauge I care about is the chamber of the rifle. This spent case can now be measured in all its dimensions for die settings, etc. In Your case, Im willing to bet this spent case will not fit in Your gauge. Case base separation almost always means excessive head space. A rifle chamber, reloading dies, and case gauges, separately manufactured, have too much potential for tolerance stacking to have any value for Me. This spent case is what I go by.
Serious target shooters start with a chamber reamer, fire cases in the finished rifle, send them off to have custom dies made, and custom chamber gauge if desired. Now You have something. Not a collection of so called SAMMI components with their range of tolerances that could easily be incompatible.
The method I suggested can get You where You need to be...Good Luck 🙂