Punch out the rear sight leaf pin and lift the rear sight leaf spring out of the rear sight base. Remove the rear sight slide from the leaf and pull the buttons and their springs out each side.
Punch out the rear sight base pins and drive the rear sight base forward off of the dovetail.Using a brass punch to drive the base off is best to minimize chance of damage.
Once the old sight has been removed you can use a DTP mount such as the one found here to mount a pair of standard Weaver / Picatinny style rings and any Long Eye Relief or scout style scope.
Helpful Hints on Soldered and Stubborn Pins
Some models are soldered into place. If so tip the barrel
upside down and apply a heat source above 180F (melting point for silver solder
FYI) and right after I see some of the solder "leaking" off I
immediately stop what applying heat and take a hammer and punch to it. Just
remember that you punch AWAY from the receiver.
You can also use Birchwood Casey Rust and Blue Remover and
apply generous amounts of it around the rear sight that it "eats"
away at the solder. I'm no chemist so I don't know if it actually does but it
always comes out after I let it sit for five or more minutes.
Most pre 40s are soldered. Some post 40 Mosins are as well. Older Mosins (1918 and below, rarely post 40s) sometimes have a set screw as well. This actually makes removing the sight easiest.
If your pins are stuck, apply some Breakfree, brake cleaner, or WD40 or some other type of "penetrating" oil and let it sit for ten minutes or so. After that they should slide right out.
Most pre 40s are soldered. Some post 40 Mosins are as well. Older Mosins (1918 and below, rarely post 40s) sometimes have a set screw as well. This actually makes removing the sight easiest.
If your pins are stuck, apply some Breakfree, brake cleaner, or WD40 or some other type of "penetrating" oil and let it sit for ten minutes or so. After that they should slide right out.
Mount installation : You may have to drill a shallow 5/32" shallow hole or indention on the mosin dovetail to accept the set screw (near the front top of the mount) to prevent any slippage due to recoil. Also use some blue locktite to secure all the screws. Otherwise it should fit like a normal dovetail mount.
