Well, I did feel enough improved to give the thing a really good cleaning (not much to do, really - just wipe the chamber out and de-gunk the magazine - it was yucky), and now it chambers perfectly. The barrel is original, being dated 1944 and, although I am no expert on these matters, it looks pristine (heck, it even glints, and that isn't a word I use lightly lol). If the rest of the rifle is in such good condition, I have to wonder why the bolt had obviously been replaced at a later date - someone just misplaced the thing?