Valve lapping compound would work fine, I imagine. Harbor Freight sells jeweler's rouge - hell, any hardware store should have it.
Mother's Mag and Aluminum Polish would prolly even do it, just lots slower.
EDIT: I just reread your post - the cruddy Commie steel seems to be softer than regular American gunmetal. It's easy to work with. This stuff is way, way softer than metal we deal with on bearing races, axles, etc.
There is a guy online who sells pre-bent Mosin bolts...
http://www.mosinnagant.net/Boltman/Boltman.html
-L.