How to check for an "undersized bolt".

[Straight Shooter]

If you don't have one of these fancy machines, you can get a very good idea (+/- 0.001) with a accurate depth micrometer and a regular "C" mic, or a fair idea with a good set of calipers (+/- 0.005).

Just measure the overall length of the locking lugs and subtract the depth of the breech face.

Headspace will be from the back of the lugs to the bolt face. So measure the length of the lugs, then subtract the depth of the bolt face. Compare that to other bolts you have.

I hope you understand the limitations of calipers. Easy to mess up depth measurements if you don’t keep it square.

Very good info, again, thank yall.
10-4 on the calipers, Todd.