I have to agree with the others: based on your description, it sounds like you had a barrel obstruction of some kind. I remember seeing a Colt SAA that had suffered a squib and then barrel split at a Cowboy Action Shooting match. It opened up the barrel for a couple of inches and blew the front sight down range. No one was hurt, but it scared the shooter pretty badly. If I remember correctly, he was going to have the remaining barrel checked and then have it cut down - it started out with a 7 1/2 inch barrel, and it looked like he had enough good barrel left for at least four inches.
Regarding the Mosin-Nagant, love them or hate them (I love them), they are not known for being anything less than rugged.
I would go back to the range and get that back, if possible. Even if you don't want to rebarrel it, there will be a lot of parts that can be salvaged.