I have a used m14 bolt and I have been wondering off and on how to tell if it is serviceable. I realize there are more than likely some largely unobtainable armourers guages but can I just check it out with my digital calipers( .0005" increments) ? If that is a possibilty where could I find the specs? there are some machinists drawings of the m14 bolt floating around maybe someone knows what the critical wear points are and I could go off them? thanks for any and all help.