An . Ar 15. Style. Pistol.
What???
Without the buttstock you can get one with a barrel under 16".
They make ‘em, and their beautiful!
Check out SIG Sauer website.
Under federal law, a rifle must have a barrel of at least 16 inches and a minimum overall length. Otherwise, it can become a "Short-Barreled Rifle" and require a federal permit.
If one does the right things to an AR15 mechanism, it is possible to have it qualify as a handgun and avoid the SBR nonsense. Others may be able to provide more details.
What???
You know, a "scary looking" pistol.