Since you haven't received replies yet, thought I'd mention that I have used two spring loaded gauges for decades. They work OK, but I would probably now spend the cash on a digital unit instead. Especially if you're setting a release. I only double check my trap gun and handguns to make sure they're OK, can't really change them, but it gives one confidence. Dirt can slow them up, sign for a cleaning due. The digitals are probably very accurate and consistent.