07-31-2022, 01:42 AM
Vin Wrote:While a pressure check can tell you the current gas efficiency of your BCG, tail, rings, etc - what it cannot tell you is its wear as a predictor of failure or indicator of need for replacement. Physical measurements with pin gages and micrometer are the best way to perform PM checks of these parts.
Pin gauges are not fool proof as some poorly machined bolt tail bores will pass the pin gauge test, yet when viewed by a bore scope and back light, the bore hole can be out of round that an air gauge would find..The same principle for using a taper gauge for the firing pin and cam pin hole with the bolt..