'Preston' - Because of the 'slope' at the front of a Krag's locking lug, it is very difficult to get consistent measurements of the lug, 'front to rear'. FWIW: two lugs I measured, (one used bolt and one NOS bolt), averaged about .406". It was possible to get widely varying measurements!

In reality, this measurement is probably irrelevant. What is more important is where the recessed bolt face ends up in relationship to the barrel breech (the allowance for rim thickness or head-space).

I see nothing grossly evident in your photographs. The lug may have been lapped.

I would get and try a new bolt, while they cost only $55.