IMHO - Unless you get a 1901 carbine sight for an absolute bargain, there is little point in paying a premium price to put a carbine sight on a 'parts gun'. (It will not make things 'more right').

The 1901 carbine sight is hard to find 'loose' and will bring $200 to $500. The 1901 rifle sight is plentiful and commonly sells for around $75.

The 1901 rifle sight has built in provision for bullet drift. The 1901 carbine sight has no drift provision. This is because the 22 inch carbine barrel did not exhibit the extreme bullet drift shown by the 30 inch Krag rifle.

The 1903 Springfield 'banded' front-sight base can accept several different heights of front blade.
It is not unusual to have to set the Krag rear-sight leaf to 200 yards, in order to shoot to point of aim at 50 yards, with a 1903 front-sight.
This is due to the 1903 front sight normally being taller than Krag front-sights.

The range distances, at which you are intending shooting your Krag, can probably be accommodated by altering your front blade height (with a file) and by memorizing (as well as, recording) the elevation setting that centers your group on the target.

Attached photos:
1. Comparison of 1901 carbine and rifle sights - note how rifle leaf (bottom sight) inclines the eye-piece to the left, as the slide moves up the leaf.
2. A 50 yard target shot with 1903 Springfield front-sight on a 22" Krag barrel. The 1902 rear-sight leaf set at 100 and then 200 yards to move group to point of aim.
3. 1903 Springfield front-sight base and commercial blade on 22" Krag barrel.
 

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