Hello Vlado, Welcome.
You might check around the site for info regarding this. If I recall correctly, some guys are not having much success shooting military ammo from their Handi's. Also, I don't believe NEF recommends using military or military spec ammo in their firearms. From what I've read the 7.62X39 is an accurate round and is in the .30-30 class as a big game round. There is non-military, commercial brand ammo available.
If you have one or decide to get one and try the mil spec ammo, be carefull with using corrosive ammo. Particular cleaning methods are needed.
As far as the big Russian goes, I have no problem getting 2-3" groups from either of my Mosins (91-30, M-38) at 100yds. Each are in issue form with no modifications. I typically use Olympic and Win white box ammo.
EVOC ONE