Changing the barrel might be a dicey affair since it may affect headspace.  I'm not positive if headspace is as important with a rimmed cartridge, but usually, it is set after the barrel is installed in the receiver... and if it's incorrect, it could affect accuracy, or worse, make the gun unsafe to fire!  This is a job for a qualified gunsmith.  There are replacement barrels available from some parts web sites like CBI ( (You need to Login to view media files and links); These new barrels will be short chambered and requires special tools to complete the chamber once the barrel is installed in the receiver.  Of course, this will also affect the value of your Krag too since it will no longer have the original barrel.