got my new barrel and also headspace gauges. kinda unsure so needing some technical support. these are ptg gauges and are simply a cylinder with the rimmed portion on the bottom. i was under the assumption that the top of a headspace gauge was taperd like the case of a cartridge toward the end. these gauges i received are labeled go and no go and o.a.l is the same. ptg numbers 156824 and 137065. they are belted magnum gauges for my 300 win mag. the difference i found is .003 at the base with a micrometer. being they are cylinders and square cut on the end where or how will my barrel hit them for space. do i have the right headspace gauges