You could set it up as an AOW with a few mods but it may be iffy. try a search here:
www.calguns.net
"An A.O.W. is a weapon classification utilized by the B.A.T.F. to categorize and restrict those weapons that are not considered to be a rifle, pistol, or machinegun. An example of an A.O.W. is a short-barreled shotgun or a pen-gun. They are class III (NFA) items, and must be approved for transfer to individuals at the federal level (with a "form-4"). Cost to transfer= $5.00"
I believe if run a single shot sled to make it a single shot during transfer you could reconfigure after registration.