Barrel length is important in establishing if a Krag barrel is Springfield Armory work or the product of 'basement gunsmithing'.

Unless I'm missing something, Springfield produced three barrel lengths:

The 30 inch Infantry Rifle barrel, likely arrived at for 'bayonet reach'. (At the time, 29 to 32 inch barrels were kind of standard for Infantry in all Armies of the World).

The 22 inch Carbine barrel, likely found sensible for convenience on horseback and of adequate ballistic performance. (Also, a good length for Pilipino Constables and Military School Boys).

The 26 inch barrel of The Board of Ordnance and Fortifications Rifle. An ultra rare experimental arm that (around 1902) pretty much showed 26 inches is as good as 30 inches.

When the 1903 Springfield rifle was adopted with its approximately 23 & 1/2 inch length barrel, some nations were going to a shorter rifle, that would meet the needs of infantry and cavalry. (The 1903 Springfield and Short-Magazine Lee-Enfield are examples. Both of these short rifles were issued with 17 to 18 inch bayonets to maintain "Reach").

Improvements in propellants and bullet ballistic design likely made 30 inch long barrels totally unnecessary.

For your envisioned 'Krag Scout Rifle', an 18 to 20 inch barrel, should give you adequate performance. With some loads and propellants, a 'flash hidder' (Like on the British No. 5 Rifle, aka - 'Jungle Carbine') might be a good idea.

(p.s. If you ''bob" a barrel, please use one that has already been 'cut-down'. Good original barrels are hard to find. There are lots of cut-downs with excellent bores).