Hey folks, I acquired a type 53 Mosin a while back. Did the usual mosin clean up, taking it all apart and soaking in mineral spirits before brushing and cleaning. The first time I fired it the bolt wouldn't open and had to be beaten open to remove the casing. Scrubbed the chamber again and have the same problem, the case has a ring worn all around the shoulder. Is there anything that can be done beyond more cleaning of the chamber?

Sounds like the brass is expanding into the groove in the chamber, not good. Other than another barrel, don't think much can be done to fix it.

So far I've only fired the two rounds, both were Tula steel. Would you think the cause is excessive headspace?

Hard to say, a pic of the fired brass would help. Have you checked the h-space ?

I have not yet but thats the next step. No pic of it but the case had a line completely around it, about the thickness of a fingernail.

Ring around the shoulder after firing is not a good thing. Barrel or headspace my guess. Not something cleaning will solve.

You might pick up a surplus barrel for a decent price.

I doubt it's headspace. If the serial number on the bolt matches the barrel, the chances of bad headspace is low. Besides, 7.62x54r headspaces on the rim.