With Mosins its not really a matter of year, but bore condition. You want rifling that extends to the end of the barrel, even if it is worn. My 1929 91/30 has worn rifling at the crown but it can get a 2 in group at 100 on a warm barrel, on a hot, from 2.5 to 3 inches, and this is with crappy Romanian light ball.
Counterboring is a process where worn rifling is drilled out, so your barrel has a few inches of no rifling which will affect accuracy. In wartime 91/30s you will find a boatload of CBed ones. I would say use JG sales and pay the extra 30 bucks to get a handpick for best bore, that will give you a good base of 91/30 to work with, from there you can leave it as it is or free float the barrel and pillar and/or bed the stock and you can end up with an excellent shooting military rifle in almost original military configuration.