NATO STANAG 5.7MM Headspace Gauge (5.7×28MM FN)

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This is the NATO spec headspace gauge for the 5.7×28MM FN.Operation:Rotate the threaded base so that the desired length has been obtained, once satisfied, lock the base into position by use of the internal screw.The value "X" is the measurement of the headspace (7mm BASIC) datum diameter to the tip of the gauge, and should be 0.7±0.05mm. NOTE! Only the exact value of "X" is to be measured and engraved on the gauge upon finishing of the parts. The value "Y" is measured upon assembly of all parts and should be 23.9±0.2mm; the measurement is the over all length of the complete assembly, or more specifically the base to the end of the gauge [if your internal screw is longer than the nominal 8mm length, do not include that protruding length]. NOTE! The value of "Y" does not need to be engraved, I only did this for demonstration purpose. The value of "Y" theoretically will change depending on the environmental conditions and should be measured every time prior to use. The correct headspace is equal to the value of "Y" - "X".