Sometimes the question has come up as to whether a barrel is an altered Krag barrel or a non-Krag replacement barrel made from something else.
In my experience, there are four easy clues to tell if a barrel was originally a Krag barrel, that may have since undergone some alteration.
1. Rear sight holes properly located and threaded (.156"X30tpi). Sometimes, these holes have been discretely 'plugged'.
2. Barrel breech/extractor-notch: Machined cut on barrel breech appears properly sloped for extractor-claw and 'timed' (indexed & aligned) with extractor notch in receiver.
3. Presence of barrel proof "P".
4. An Index mark on barrel lines-up with mark on front of receiver ring.
p.s. Note - This does not mean that a barrel is the original one on a Krag receiver. It just helps identify barrels that are of U.S. Krag origin.
Krag barrels were proofed, completed, and finished, before installedon a receiver and seem highly interchangeable.
(The diameters and taper of Krag rifle and carbine barrels is the same from breech to 22 inches from the breech).
