The ATF has some, shockingly, pretty well detailed information on this:
https://www.atf.gov/firearms/machinegun-destruction

The funny thing about this stuff is if the machine gun doesn’t meet these regulations it IS a machine gun. And in this case, probably an unregistered one.

It would hurt me emotionally but if I had that thing in my possession, I’d be firing up the oxy-acetylene torch as fast as I could. My gun rights are too important to be tip-toeing any legal fine lines.