Thanks for the info and pictures. I have never seen those markings on a Springfield Armory barrel- the numbers on the chamber face of the barrel. It also looks to have an old dovetail cut behind the rear sight screw holes. I suspect it is not an arsenal barrel and may have been made with slightly different bore rifling cuts. That could answer the unusual measurements you got.

It's great to hear, though, that you are getting it to shoot well. Lots of fun with a Krag in almost any condition!

Keep up the good work.