The National Firearms Act of 1934 requires a $200 tax on machine guns.
The Firearm Owners’ Protection Act of 1986 limits machine guns to government agencies, and to those machine guns lawfully owned before the effective date of the prohibition. The Act prohibits civilian sales of newly manufactured machine guns.
It is not a Federal crime to own a legally owned machine gun, but it costs a lot of money, because the supply is limited to those legally owned prior to 1986. (In 1986 I should have invested my pension money in machine guns instead of stocks.)
If I remember correctly, the machine gun ban was placed in the 1986 gun reform law by democrats in hopes of killing the entire bill.
Before that time, the 1968 gun control law was in effect basically banning all firearms sales over state lines, and banning the import of “Army surplus rifles”, a democrat desire in response to the Kennedy killing, but really to protect New England gun makers from cheap competition.
About time the un-constitutional gun laws got the old Heave ho!