anywhere you get ak ammo should have 7.62x54r. hoppes #9 will remove corrosive salts as it was originally formulated to keep corrosive ammo fom affecting firearms.
it can often be found in 880 round crates.
RGUNS - Ammunition
i bought my last crate of 880 from them. but i picked it up in person its only about a 50 minute drive. their cart app will calculate shipping costs. its 28$ to have a crate shipped to me.
when my crate is done im just gonna reload for it. there are prolly ftf vendors that can supply ya too if you cant find it local.
my local walmart even has some on the shelf.
make sure you give it a super good detailed cleaning.
i dont like linking to sites with other forums but this page http://7.62x54r.net/
has about everything you could hope to know about the mosins. make sure you strip the bolt down and make sure the gun has no cosmoline left. hoppes #9 gets rid of cosmo off metal pretty well too.
if you got a bayonet they are sighted in with the bayonet extended so if yours is off a bit extend the bayonet before mucking with the sights
this tool is a necessity to properly maintain the bolt
the middle notch is for checking firing pin protrusion the screwdriver end fits the end of the firing pin. the notch closest to the circle end is for removing and replacing the firing pin. if the pin hits the center notch its too far and needs to be back out a bit