I have a couple Mosin-Nagant rifles and they are fun and cheap to shoot. However, I wouldn't put much money into mine. I would hate to have to fight in a battle with one of these. The accuracy isn't bad for the first few rounds but can be measured in feet when they heat up a little. With that said, a Finnish guy named Simo Hayha had over 500 Sniper kills in 100days against the Russians with one with open sights. I guess he didn't let it heat up.
Yours might be really accurate so don't let me dissuade you from upgrading yours. I would like to see a pic of your set up.