NB'chuck':  The 6.5mm M-S and 6.5mm Carcano are very similar cartridges.  I have heard of a number of Norwegian Krags altered to the once popular and available M-S round.  Back in the 1950s, 6.5 Carcano was rare in hunting loads.  In fact, M-S brass was used to make reloadable Carcano ammo.  The Carcano round is just an unlikely candidate for re-chambering.

You may have to resort to having a chamber cast done to accurately measure your chamber.  (I no longer have any 6.5mm M-S brass laying around.  Otherwise, I would send you some cases to play with).

Here are some dimensions from one reference:

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