re: Updated: Full auto lower laws.. Answer from ATF on page 2

no because the reason you don't need a form 1 for your pistol AR is because it doesn't have a shoulder stock. Same reason why you don't need a form one for every glock pistol you own unless you were to go add a shoulder stock to it which would then make it an sbr requiring the form 1. So because you have the ability to use the 10.5 inch upper as a pistol you don't need the form 1.