'chuck':  Welcome to the KCA forum.
  It is most likely your Norwegian Krag had its barrel 'set-back' by shortening at the breech end and was re-chambered for the 6.5 X 54mm Mannlicher-Schoenauer cartridge (a lined chamber is also possible).  This type of conversion was done back in the 1950s, when '6.5 Swede' was hard to get and 6.5 M-S was available in North America.  (BTW - Norwegian Krag barrels have a left-hand thread).  Inspection by a very experienced and knowledgeable 'gun-guy' is advised.