Ryan, I think you are wrong on one key point. If you are buying an SBS from and individual, or making one, you have to be 18 because it is a shotgun. However, and AOW is considered a pistol, and in many states, the age to possess a pistol is still 21. In a state like Indiana, where you can possess at 18 but have to be 21 to purchase, the aforementioned manufacturing route would work. But your local senior LEO will probably put the kabosh on the forms for a 19 year old to make an AOW, and in many states, would have legal grounds to do so.