The easy way to make and gauge 9mm Luger is to use a calibrated chamber case gauge like one of these:
https://www.midwayusa.com/product/1018249683?pid=793368
These cartridge gauges are inexpensive, and will save you more in time as you reload than any other method.
They come from a number of companies.
I 100% inspect my reloaded ammo with these gauges. Drop in the cartridge, Let it fall out and put the finished gauged cartridge in the box.
https://www.youtube.com/watch?v=hIraXq6u0VY
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Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.