Never seen a 1903 Springfield barrel up close. It would have to have a portion of the chamber cut off to ream for the smaller 30/40 cartridge. Depending on what the smith wanted for over all length would determine how much he cut off. Maybe there was a published guide so most came up 23 inches? Or did one company supply a lot of partially converted barrels so you see similar details in many examples?
You example shows a course extractor cut extractor cut maybe done with a broach or shaper. Also indicative of a production set up using the known clocking of Krag barrels. The one Krag barrel I have on hand was done with a rotary mill cutter much like the one in my sporterizing photos.