No Stock = pistol, regardless of barrel length.
Add a stock, it’s a rifle and barrel must be 16 inches or more.
If the barrel on a rifle is less than 16 inches, it’s a “Short Barrel Rifle” and subject to taxation and registration as a Class III firearm under the terms of NFA of 1936(?).
AK47 pistol? Sounds good to me.
NFA 1938 but who’s counting LOL!