One of the ways around the full auto ban is to optain a class three FFL license. Then, as a class three dealer, you may obtain a full auto weapon as a dealer sample to sell to military or police units.
This is not cheap. You need a shop (your home does not qualify), insurance, an annual fee for your class three license. The BATF can also pull your license if you fail to show any sales.
Some class three dealers rent their new dealer samples to the general public. This is the easist way to get your hands on a leagal full auto weapon and give it a try.