johnn,
I can relate with your cleaning woes. I have taken on a few dark mil-surp bores too. A couple of Swedish Mausers and a few Norwegian Krag-Jorgensens. Like mentioned above, I will do a long regiment of Hoppes 9 on patches wrapped around a bronze brush. Then move to JB nonembedding bore compound with patches wrapped around a brush. I always assumed I was contending with alternating layers of copper and carbon with shallow pitting below. Seems like even with the rough bores in the end as long as it has stronger rifleing I have ended up with a decent shooting iron sights rifle in the end (at least by my standards). I have been lucky in those regards. After that thorough cleaning the groups might not improve until after 10 or 15 shots. If you do decide to rebarrel remember the Norwegians used a left hand thread on their Krag-Jorgensens. Good luck with the project and let us know how accuracy comes out. I do love working with the Norwegian Krags.
Happy hunting,
sixfive
