As long as it was a registered NFA transferable machinegun built before May of 1986, it could be legally bought and transferred amongst the civilian peasants, as long as you were not a felon and 200.00 went to the NFA tax every time it changes hands, to this day, with an intensive Federal background check, after your fingerprints and 200.00 are recieved in Washington, along with the signature of your County Sherrif, stating you are a fine upstanding citizen in his county, in Black ink.You would've had to own one prior to 1934, when the class 3 stamps came into effect. I believe it was. Honestly I've had access to select fire weapons for a long time. I've used them in tactical and training situations and personally I don't have a use for full auto, 3 round burst maybe. A belt drive machine gun is another story on a battlefield. Did you know that there was a time some firearms were made without serial numbers before 1968.
Not sure if that's racist or not, and don't really care.
Or have a trust set up, and I never went down that street, so I'm not educated enough to say quite how that works.