I have Lyman ammo checkers for 9mm, 45acp, 223 and 308. I think I have other brands for 300wm and 45-70. To me they are indispensable for reloading. I gauged some rounds for my 308 that were a c hair above the top of the gauge. I thought that it would be good enough. Nope, couldn't get the bolt closed. Same thing with 9mm. Gauged all my rounds. For some that were a c hair above would fit my M&P but not my Shadow 2.
I won't even bother bringing any rounds of any calibre to the range for any of my fireamrs unless they pass the plunk test on the gauges. Whenever I start reloading for any new round, I always get a ammo checker gauge and I always search out Lymans.