FWIW - A lot of the competitive shooters on the KCA Forum seem to use and prefer 220 grain RN projectiles and IMR or Hogdon 4350 propellants. With the projectile moving near 2,000 FPS, they find a good agreement with their original sight calibrations.

If you view older threads on this section, (numbers at bottom of page), you will find some relevant loads and discussion.

The nice long neck, on the .30-40 case, allows seating most projectiles to a generous OAL. The controlling factor is 'fitting in the magazine'.

Individual Krags vary in their ability to feed 'pointed' bullets. Sometimes, different Left side-plates can give better feed.

The U.S. Krag was designed to feed the 220 grain RN.

Most Krags tolerate 180 grain hunting projectiles well.