Mark - Hopefully, you have access to a good gunsmith.
Do not let a 'Klutz' damage the rear sight holes on your barrel!

Do No Harm!

Krag (rear-sight) screw-threads are kind of rare (.156 inch X 30 TPI). You will not find replacement screws at the local hardware store or most gun shops!

I have had good success removing the cut-off screw shanks. (People, use to, cut the heads off of the sight-screws to fill the tapped holes).

My method is to lightly center-punch the remains of the ('cut') screw. Carefully, drill a fine hole deep down the center of the screw-shank. Wipe some 'liquid wrench' around the barrel sight-screw area. Tap a small screw-driver into the shank for a 'friction fit'. Then unscrew the 'headless' screw.

This has worked for me four or five times with no damage to the hole or female sight-screw threads.

Do No Harm!

p.s. It would be a good idea not to shoot this Krag in its current state. There is no barrel-band holding the barrel solidly in the stock's barrel channel. It is real easy to crack a Krag stock when the barrel lifts and puts stress on the (close together) trigger-guard screws.