If you want to scope your Mosin you can also go for a different solution. "The Brass Stacker" makes a picatinny rail for the Mosin and you wont even have do any modification to it. All you have to do is pop out the two pins on the rear sight and it fit right on there. Then put on a pistol scope and you will shoot 1 MOA groups at a plus 100 meters. You can still use the iron sights with the rail mounted. There is quite a few advantages to this solution, the bolt handle one of them. Here is a link Mosin Nagant | Brass Stacker
Scoping your Mosin without any mods is quite a cool thing.
There is a list on the CMP page of all the affiliated clubs by State - but CMP is a great option. I've been a member for years.
COL, U.S. Army (Ret.)