Did you try to chamber the Jarmann military cartridge? Using a dummy would be best of course.
In 1975, I met Martha Gilson. She was the widow of an Arctic geologist & mining engineer. I buried my friend in 1993. In the time between, I listened to her stories. Martha spent the winter of her 21st year on Svalbard (1917) and from 1919 to 1928 lived in Tromso, Norway, & made many winter trips. She became an accomplished photographer, as in Natl Geographic. She said that on Svalbard, everyone carried a rifle wherever they went because of the bears. She carried a Nor. Krag sporter, with one in the chamber, safety on, & a full magazine.
Martha said that in the far north, once out of town, money was useless & that cartridges took the place of money. The only rifles of value were those chambered for one of the Scandinavian military cartridges because you could get more ammunition. The rest were useless when the ammo ran out. She also said that sporting rifles were marked as being chambered for proprietary cartridges for political purposes(& mentioned the 256 Gibbs) but if you tried to shoot military cartridges (6.5 x 55 in the Gibbs) in them, they worked just fine.