CoRoMo
Member
Not on a machine gun. And not on a SBR.Barrel still needs to be 16".
As Sam posted,
Having determined that the weapon was manufactured this way (or at least you have reason to think that it probably was) there is a pretty good chance that the paperwork WAS done. Manufacturers only send out guns to dealers. Manufacturers only send out NFA guns to Class 02 dealers. Class 02 dealers don't sell NFA guns without a Form 4 -- it isn't worth the risk.
By all indications it is either a machine gun or an SBR made in 1980. Like Sam states, it would have been made, distributed, and dealt according to law in 1980. Unless the grandpa stole the gun or cut the barrel, it is quite likely registered in the NFRTR to him. I'd operate under that assumption until the ATF responded to the attorney's letter. I'd also want that Thompson at the Florida residence rather than Illinois.
I know that not everyone would, but I'd hold off screwing up what might be an extremely valuable item until I knew what it was.