I can identify the sound of a 7.62-39 that is fired out of an AK-47. Many other rifles also fire this round. If it is fired out a a short barrel like the Draco Pistol I would have no idea what weapon it was fired from or even if it was a 7.62-39. Unless you have the weapon in your hands, you do not know.
If you have to go to the time and expense to get an semi in NJ, why get an AK-47?