Only a couple of basic things that can be throwing you off: one is barrel wear/damage and the other is ammo quality. Fix both of those and you probably won't ever better the gun. If your barrel is shot loose, you can try loading larger diam bullets to fit your bore size....and if it's the muzzle/crown damaged, slice the barrel back to good rifling and recrown it. If it's ammo quality, good commercial ammo will fix your prob.
The #1 thing you need to do is to get your bore slugged....force a bead of lead up the bore til it pops out the muzzle to see your exact bore size. You'll need to handload your own ammo with that sized bullet for best accuracy. Commercial ammo can sometimes be found to match that bore size, too, but not always.
Crown, as said, just slice the barrel back a few inches to some good rifling and recrown it. Instant fix.
Ammo: firing milsurp ammo is ok most times but not always best for accuracy. Diff makers/factories made different quality ammo. From experience, silver/yellow Hungarian is as close to match ammo as you'll find in the MN. Anything less will be progressively worse. You can often buy milsurp and reload your own, though. Not fully reloading it, milsurp brass isn't often reloadable due to the primer type. Just select a hundred of your best condition cartridges/bullets, same maker/same stamps etc, and use a bullet puller to jerk the bullets. Dump all the powder into a large pile and then use a powder scale to weigh it and divide it by 100 to get the average. Load that EXACT amount back into each casing. Weigh the bullets next and pick out the exact same weight ones, put the lighters and heaviers to the side. Replace the good ones in the casings and recrimp them. The rest, replace/recrimp the bullets and toss them back into your blaster ammo box. You can even reload those averaged casings with aftermarket hunting bullets to match your slugged bore size.....just be sure to buy and use bullets that *exactly* match the weight of the ones you jerked out. If you don't have a good scale and a crimper, don't try this. Lee makes a handloader in 7.62x54r if you can find one. Try MidwayUSA.com. If anyone has it, they will.
And I have three MN's. Good guns. Congrats on yours. Too many newbies and "experts" think buying accuracy makes them a better marksman. It doesn't. You don't see Olympic shooters using lasers etc. Addon crap is like a crutch. It only makes you weaker as you become dependent on it.