I think one needs only one gauge for checking bottleneck cases for one important size issue. They'll also need one good caliper to measure those cases for all the other size issues. These two measuring tools are plenty.
Use the caliper (digital or analog) to measure case diameters and length. Can also be used to measure neck wall thickness pretty accurate. A 4" one is good enough unless you need a longer one.
Use a case headspace gauge (RCBS Precision Mic or the Hornady one) to measure where the shoulder is on cases. Measure the case headspace (head to shoulder) dimension on a fired case, then set the full length sizing die in the press to set that shoulder back 2 thousandths after it's sized.
That's all folks.
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Former USA Palma Team Member
NRA High Power Long Range High Master
NRA Smallbore Prone Master