Louis:  Later types of Krag cutoffs usually function with earlier U.S. Krag actions.  The length of the cutoff shaft is not relevant.  On later cutoffs, when the lever is rotated to the 'up' position, it turns the flat surface of the shaft even with the inside wall of the receiver.  This allows cartridges to be fed into the path of the bolt.  When the cutoff lever is in the 'down' position, the round surface of the cutoff shaft projects from the inside wall of the receiver.  This 'bump' catches the cartridge rim and prevents the reserve cartridges from being picked up by the bolt.  (The earlier cutoffs worked on the same principle but the lever positions were reversed.  I believe these were replaced to avoid confusion.  The later cutoffs have a polished area that shows when the lever is 'up'.  This was so your sergeants and officers could easily detect if you were in "rapid-fire mode" and not holding your magazine in reserve.
  If your cartridges are not smoothly entering the chamber, it is more likely a problem with the over all cartridge length or the contour or shape of the bullet.