Obviously we all know how AKs work more or less and to some extent, otherwise we wouldn't be posting here and showing off our AKs.
Now for those that also have AR-15s, you also know how it works, more or less (gas system, but a much smoother system with tighter clearances for the bolt, etc...)
The 7.62x39 AR-15s, using 7.62x39 ammo that we'd use in AKs (Wolf, Brown Bear, Purple Bear, Fuschia Bear, etc...), match the accuracy of .223 up to about 200-300 yd, since out past 300yd, the 7.62x39 bullet (using standard loads) will drop significantly and be affected by wind drift.
This leads me to believe the "inaccuracy" of 7.62x39 AK variants is mostly in the AK design itself, and not because of the cartridge. This would also explain how AK variants that are designed to slow down the gas piston or at least smooth out the action, will yield very good results using quality ammo.
It's not mainly the bullet or the load, it's mostly the rifle and the shooter.
My AR-15 shoots about 2-3" at 100yd using XM193, and about 2-3" at 100yd using Wolf .223