You need to acquire an sbr stamp for your lower, get it engraved, then you can buy the shorty upper. Or you can buy a pistol lower for it and run it as a pistol.
Aac is the best source i would think since its their baby
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." — L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...
"I crapped my pants to avoid the draft!!" -Ted Nugent