139 grain bullet --
from wikipedia article:
    * 6.5x55 a 6.5 mm (0.256 in) rimless round. Most variations are loaded for a chamber pressure of 350 MPa (roughly 51000 lbf/in²). Early rounds, with a 10.1 grams (156 grains) long round nosed bullet (B-projectile) had a muzzle velocity of around 700 m/s (roughly 2300 ft/s), while later rounds with a 9 grams (139 grains) spitzer bullet (D-projectile) offered a muzzle velocity up to 870 m/s (2854 ft/s).[1]

Note that 51Klbf would be altogether too hot for the US Krag which has a larger base and has intended clearance between bolt handle base and receiver, those tend to crack lugs with high pressure loads. 

The machining on Norwegian version is different, bolt handle base is supposed to bear on receiver as well as bolt locking lug, to give effectively 2 locking lugs -- it is supposed to be able to withstand higher pressure than US Krag.