While I haven't, I too am trying to see if I can buy one and get it shipped into my State.
However, I did build an upper for my M4 in 7.62x39mm using a mil-spec 18" HBAR-profile barrel and a JP Enterprises adjustable gas block. I find it inherently significantly more accurate than the same round out of any SKS or AK, easily by a factor of 2 or 3X. Using soft-point 125-grn deer hunting ammo she consistently shoots sub-MOA out to even 200-yards.
The limitations on my build though, are the magazines! The tapered round of the -39mm round just does not want to feed in a 'straight up' magazine. The concept of using an AK magazine I think is fantastic!
They use to say ... "If you can't hit it with an AK, you can't kill it with an AR". Well, I personally think that the -39mm cartridge mated to a superior accurate firearm design like the AR is a Win-Win!