The term 'NFA firearm' refers to those that fall under the specific definition of a 'firearm' in the National Firearms Act; and must be registered with ATF for legal ownership/possession. It's not the 'normal' definition of a firearm. This is the definition in 26 U.S.C § 5845:
The term "firearm" means (1) a shotgun having a barrel or barrels
of less than 18 inches in length; (2) a weapon made from a shotgun
if such weapon as modified has an overall length of less than 26
inches or a barrel or barrels of less than 18 inches in length; (3)
a rifle having a barrel or barrels of less than 16 inches in
length; (4) a weapon made from a rifle if such weapon as modified
has an overall length of less than 26 inches or a barrel or barrels
of less than 16 inches in length; (5) any other weapon, as defined
in subsection (e); (6) a machinegun; (7) any silencer (as defined
in section 921 of title 18, United States Code); and (8 ) a
destructive device.
The only question is: On a rifle with the minimum 16" barrel and a folding stock, do you measure for overall length with the stock folded or open? I have regularly seen this answered
both ways. I was once told by an ATF agent that if it can be fired in a normal manner, with the folding stock folded, collapsed, or removed, it will be measured in the shortest configuration. Then too, the Kel-Tec SU-16C can be fired folded and is listed at 25.5"! So ....
I wonder if you could register a Handi receiver with ATF as an NFA gun, then use whatever barrel length/stock configuation you want/ Hmmmm.......
