If you want the highest level of precision and control, this Burstfire Primer Pocket Go & No Go Gauge Set is it. But keep in mind there are variations from brand to brand, and lot to lot. Cup thickness is a factor in if it will fit or how easily it will fit as well. Never guess again if your primer pockets were properly reamed or swaged. Enlarged body, curved (go gauge) / Swirl (no-go) design for a secure grip to be held by hand. It can also be attached to an existing industry standard 8/32 threaded hand tool handle, to maximize comfort.We all want a tight primer pocket, that will not loosen up before our brass fails. Especially if you use expensive brass. Using small primer pocket as an example: The small gauge is made to 0.1725. Variation for small primers is 0.1745 - 0.1755 in diameter. Majority of small primers will be 0.175". A 0.175" primer, can be inserted in a 0.1725" pocket on a press, but may meet some resistance at 0.1755" (Will not work in most cases if hand priming. In ...