There was an excellent article some years back in the gun digest on various calibers done I believe in Finland. I'm going from memory but seem to remember 6.5, 7.62, 375 and a few others. So in all probability your choice of caliber isn't out of reason. There was one article somewhere in that a moisin was rebored to 50-70 with some stout loadings. Might have been in the CBA fouling shot journal. Check the CBA website see is the article is available. But the rifle was only a single shot, had the cut in the receiver filled and welded. Frank