Tark; while that may be true for Mausers, which were built by Teutonic uberengineers, Mosins were designed by S.I. Mosin in the Russian tradition; loose tolerances to survive the Russian winters, and still work. Russian-made firearms have a history of being robust, solid as a tank, and loose as hell. Yes, they lock up well enough in critical areas, (Bolt head/reciever, cartridge/chamber) but they are not the precision machines the Germans took to Stalingrad and died with when they malfunctioned on them.
Even when they loosened tolerances with subsequent models, (StG44, MG42) they were still overengineered. (Look at a Haenel model StG44 once)
M.T. Kalashnikov looked at the StG44 and said to himself, "Now how can I adapt this to Russian conditions and methods of manufacture?" And *BANG* the AK-47 was born.
No, I doubt paladinj's problem is from the bolt coming from another rifle and not fitting. If this were the case, most of the Mosins around would have that problem, as during two World Wars and the subsequent refurb program follwing the second one, lots of Mosin Nagants have different bolts than the ones they left the arsenal with. Most of mine do, and I've noted this among my fellow memebers of the Russian Mosin Nagant forums also. Perhaps paladinj might post his quandry over there?
http://russian-mosin-nagant-forum.com/
I am entropy on that forum also.
This case had a clawmark that scraped the steel right up and left a visible burr on the case. This clawmark is about 1/4 of the way up from the rim and way past where I would expect the extractor to ever engage. It is a big shiny streak with a curled burr of steel on one end of it.
Does this mean I have a bad burr in my chamber? What to do?
You probably do. but without good photos to look at, I couldn't diagnose that. I recommend taking it to a gunsmith to have it checked and repaired if so.