Well, you would DEFINITELY have to file the paperwork with the ATF and pay the $200 tax. The ATF would consider any weapon with a barrel length under 16" and a rifle stock to be a "Short Barreled Rifle".
Hang on.... I'll try to find the law...
Ok.... here it is....
A semiautomatic rifle that has an ability to accept a detachable magazine and has at least two of the following characteristics:
a folding or telescoping stock
a pistol grip that protrudes conspicuously beneath the actionof the weapon
a bayonet mount
a flash suppressor or threaded barrel designed to accommodate a flash suppressor
a grenade launcher
A semiautomatic shotgun that has at least two of the following characteristics
a folding or telescoping stock
a pistol grip that protrudes conspicuously beneath the action of the weapon
a fixed magazine capacity in excess of five rounds
an ability to accept a detachable magazine
A semiautomatic pistol that has an ability to accept a detachable magazine and has at least two of the following characteristics
an ammunition magazine that attaches to the pistol outside of the pistol grip
a threaded barrel capable of accepting a barrel extender, flash suppressor, forward handgrip, or silencer
shroud that is attached to, or partially or completely encircles, the barrel and that permits the shooter to hold the firearm with the nontrigger hand without being burned
manufactured weight of fifty ounces or more when the pistol is unloaded
A semiautomatic version of an automatic rifle, shotgun or firearm
Any of the weapons, or functioning frames or receivers of such weapons, or copies or duplicates of such weapons, in any caliber, known as:
Norinco, Mitchell, and Poly Technologies Avtomat Kalashnikovs (All Models)
Action Arms Israeli Military Industries UZI and Galil
Beretta Ar70 (SC-70)
Colt AR-15
Fabrique National FN/FAL, FN/LAR, and FNC
SWD M-10, M-11, M-11/9, and M-12
Steyr AUG
INTRATEC TEC-9, TEC-DC9 and TEC-22
revolving cylinder shotguns, such as (or similar to) the Street Sweeper and Striker
Looks to be illegal, so far as I can tell.