The AK, though perhaps the most successful weapon in history will never group like an AR. Its a simple mechanical issue, and changing the reciever type will not help. The Vepr is one attempt at that, and though they are pretty accurate (about 2 moa, 100 yards), the mechanical differences between the AK and AR is the root cause of the accuracy gap. I wont bother to explain both mechanisms because im sure you are versed in their operation. However I will say this, the large moving mass that is the AK bolt, bolt carrier, and gas piston assembly causes alot of vibration and shock shot to shot (no a recoil buffer will not help this, usally they only aggrevate it). This inherantly affects the stability and therefore accuracy of the weapon, also the movement of the bolt carrier assembly is tethered to the barrel by the gas chamber, causing a fluttering of the barrel after each shot, you can actually see this effect with high speed cameras. Next the machining tolerances are nowhere near comparable. The AR is tightly machined for precision operation, the AK is more loosely machined for unbeliveable reliability. Its a trade off. And lastly, and perhaps most significantly, the bores and chambers of AKs can be anywhere from .310 to .311 inches in diameter, again, this was done intentionally to ensure correct feeding and cycling of the weapon even when the worst of ammo is used. All of these decisions were made intentionally and are clearly tradeoffs for reliability. I love my AK, more than any other rifle, I understand its strengths and limitations. Even though it will never group like your AR, do not ever underestimate the AK, practice has a HUGE affect on your accuracy with it, FAR FAR too many of our countries finest have been struck down by this weapon. NEVER underestimate it, no matter how much the AR guys bash it.
REMEMBER, the AR is more reliable than you might think, but the AK is more accurate than you might think.