Not 0.005, 0.0005...
I'm curious too. It seems to me that if the operating system was that sensitive to five ten-thousandths, ammo would be a huge issue. That's awfully small number when dealing with propellants that have different burn characteristics that would clearly be impacted by humidity, altitude and temperature.
ETA: It would be very expensive and just plain difficult from a machining standpoint to hold five tens through machining, heat treat and hard chrome.
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