While measuring from front of receiver ring to the bolt face and extractor on a 93 mauser, measuring twice(more like 10 times) to finish ream once the numbers changed a lot too the tune of almost 10 thousandths. I took the action out of my unairconditioned shop to my unairconditioned den. The measurements were taken over about 45min along with other measurements. Because of 50year old eyes and infrequent depth mic. use my readings were sloooow! I was also up close to an incandesent bulb desk light so I could read the mic. With the heat from my hands and the light could the 1 inch rod in the mike have expanded that much? I'm not reaming yet nor will I till I get several repeatable readings.
Thanks Aaron