U.S. Krags (all made at Springfield), unlike Norwegian Krag models, have clearance between the rear of the bolt guide-rib and the receiver.  (On Norwegian Krags, bolts were fitted to make contact at both the locking lug and guide-rib).  When they got into Civilian hands, some U.S. Krag bolts had the rear of the locking lug 'lapped' so that both the locking lug and guide-rib made contact with the receiver.  This was probably 'OK' and sound engineering, if a barrel was being fitted and adjustment was made for the added 'end-play' and increase of head space.  If no adjustment was made, the potential exists for excessive head space.
  I have only owned one Krag that had excessive head space.  Cartridges fired in that rifle showed obvious case stretching.  The bolt in that rifle appeared to have had metal removed from the rear of the locking lug.  The bolt's guide-rib made contact with the receiver.  The problem was solved by replacing the bolt.
  Today, I measured the guide-rib clearance on three model 1898 Krags.  The bolts were stripped and pulled rearward so that the rear of the locking lug made contact with its recess in the receiver.  A 'feeler' gauge was inserted between the guide rib and receiver.  Clearance varied from .003" to .004" on the three rifles.  I also examined a fourth Krag that was re-barreled by Sedgley.  The guide-rib made contact with the receiver for a 'double lock-up'.  However, the 1905-SA barrel, re-chambered for .30-40, was fitted for correct head space.
  If you encounter a U.S. Krag, and the (stripped) bolt guide-rib has no clearance with the receiver, it could be a Red Flag and may have excessive head space.

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