FredC wrote on Sep 20^th, 2019 at 4:38pm:

Next surprise the locking lug's working surface is NOT ground. It shows machine marks as well as the case hardened surface. This will give a way of guessing at wear of the bolt. The first attached photo shows a bolt that has not been used in 80 years as well as one of the new bolts. The lightly used lug shows a shiny spot (circled) covering about 20 to 25% of the surface. So most of the lug has never touched the corresponding surface of the receiver.

I had too much trivia in post #13, so I thought it may be beneficial to mention estimating wear again.

The most meaningful way I can think of to estimate wear on the locking lug will be to estimate a percentage of wear to original surface  area on the inside of the lug. So on the bolt on the right the shiny area(worn is about 20% of the original surface, so lets call that one 20% wear. If the whole surface is shiny we would call it 100%. If it is 100% it could have all the surface worn just a .001 inch (relatively new) or it could be worn and lapped .010 inches like my sporter, but the percentage and measurement together will give the best guess as to its current status.

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