I'm guessing that the reason AK's in the mosin caliber are not widely available is because the AK was designed to be able to shoot full auto and muzzle rise would be a problem. There are some in .308, so it should be feasible to chamber them in 7.62 x 54. They would probably sell well in the U.S. at least. A mag of 30 would be heavy, recoil probably stiff but mitigated somewhat by the gas action. I would probably buy one. Another reason would be that the 7.62 by 39 is plenty powerful for human targets and the AK was not designed as a hunting rifle. Guess I answered my own question as I am thinking about it.