The Russian Arsenals countered bored Mosin Nagant 91/30 Rifles probably by the millions.  I have 5 that are counter bored. They are bored to about a depth of 1 to 1.25". The new internal crown is quite square to my eye.  If you look at the end of the barrel it is hard to tell unless you look real close. The ones I have were bored out to around .325 to 327. The counter bored rifles that I have shot have more than acceptable accuracy for a 100 plus year old rifle.

If the OP's Krag is not real collectable. a counter bore will likely make it a much better shooter.

Zgun