Yea I'm think about throwing a 4x scope to see if I can get 500-600 out of it, but that's asking a lot.

If you get an American optic you might be able to at least see the target that far out but conventional battlefield doctrine puts the max effective engagement range for a battle rifle like that at about 400m. That's one reason why the Russian POSP optics only have a range finder for 400m max. If you can find a Russian optic, avoid Kalinka good optic crap price, and you have the original side rail a POSP will serve you well. I tried an American red dot and it wasn't a good fit. All the after market Weaver and Picatinny rails you can get seem to be mounted on the least stable parts of the weapon, like the gas block or the dust cover. The receiver mounted side rail seems to be the best option for consistent zeroes, unless you find it relaxing to bench shoot.

Yea I found a Russian based company that sells the rails, since I already have the bracket on the side of the receiver. I was planning on just popping on a Weaver 4x they have always served me well on my ars.

If you can get a Weaver that mounts to that bracket that would be another good way to go. My Arsenal they mounted Weavers in really obnoxiously useless spots luckily it has a milled receiver with the receiver mount so I do have that one super stable option. Another good thing about the old Russian POSP optics is they have a diode that illuminates the retical. 90% of them are broken but, I found that if you drop the right size spherical tritium insert into where the diode sits it fits perfectly and you have a battery free illuminated optic. Not quite a Meprolite but it works and you don't have to worry about the battery going dead in the field at inconvenient times.

Good idea with the psop I'll have to look into it