'MiHeadShot' - Welcome to the KCA Forum!

In my opinion, your question is a bit difficult to answer. With the Krag there were some 'growing pains'. Everything was kind of new and under development during 1892 to 1900.

The Ordnance Department chose a 220 grain round-nosed jacketed bullet.

Suitable bullet-jackets were proving problematic.

Smokeless powders were being developed and the good ones were primarily European, (involving royalties)
There was chemical instability and serious barrel erosion problems. The U.S. did not have a good Domestic Powder for the Krag, until "Whistler & Aspinwall .30", in the early 1900's.

Initially Primers were Mercuric and very corrosive, causing problems with reusing Brass and aggravating bore deterioration. Eventually more benign chlorate primers (also,corrosive) were adopted and remained in U.S. military use into the mid-1950's.

With original U.S. Krag barrels it is not unusual to find .3095" groove diameters. Some barrels are 'tighter' and some bores more excessive.
It is hard to find original 30" Krag barrels with Fine bores.
New commercial barrels (like Criterion) will have .308" groove-diameter and will be mint.
Because they were made for 220 grain RN projectiles, the chamber of original Krag barrels has a long 'Lead'. Many Krag barrels will show a degree of throat erosion.

All this being said and in my opinion:

With current 'jacketed' .308 diameter projectiles (of 150 to 220 grains), appropriate propellants & loads, and reasonable shooting skill, it is realistic to have 2 inch groups at 100 yards with a Krag rifle, even if the bore is less than pristine.

A lot of KCA members post results of under 1.5 inches and some achieve 1 inch (5-shot groups) at 100 yards.

I say, under 2 inches at 100 yards with original sights (and old eyes) is good shooting.

p.s. Our ammo is better than their's was, 'back in the day'.