Interesting stuff indeed!
So it would appear that a gauge with a rim diameter of .800" should fit into the gun's chambers to a depth of 2 1/2" (from the breach face) for a gun proofed at 2 1/2". If it goes to a depth of 2 2/4", the gun's chambers were likely let out to accomodate longer shells, thereby remdering the gun out of proof. Correct?
Could there be any other inferences made?

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