But in some states in USA, cannot you simply convert a semi auto AK to a fully automatic? I know in Oregon all you have to do is get a special license for $300 and you can own fully auto rifles. I was told it is not so hard to convert semi auto AKs to fully. I am not sure about ARs.
The 1986 FOPA law had the Hughes Amendment that froze the number of machine guns for civilian use. These are called "transferable" machine guns. Any new machine gun regardless if originally a machine gun or a converted machine gun that was produced after May of 1986 is a "non transferable" machine gun in which those weapons can only be possessed by government entities and personnel and of course the manufacturers themselves. Civilians are a no go.
A civilian can own one as long as they pay the $200 tax and it is legal in their area BUT that machine gun had to be registered before May of 1986.