To give the OP a direct answer- yes- there ARE full autos that a private citizen can own in the US- IF your state laws do not prohibit it.
Only those full autos already registered with the BATFE by May 1986 can be transferred to a private person. NO ADDITIONAL full autos can be registered except by dealers supplying Law Enforcement AGENCIES or the military.
The transfer must take place thru a machine gun dealer in your home state. You must be 21. not prohibited from owning a gun, apply to the BATFE for approval of the transfer, file the application, together with your photo, prints, approval from local Chief LEO, payment of a $200 transfer tax, and a jar of Crunchy Peanut Butter. (Just kidding about the peanut butter) Approval seems to be running 6-9 months.
Since there is a finite supply of pre 1987 guns, prices are up. A Mac will run you a few thousand. An M-16 about $15,000. An M60 belt fed- Jesus wept.