Depends on your state.
In most states, the FFL must pay an additional tax (SOT- Special Occupation Tax) to handle class 3 firearms. These would include machine guns, suppressors, and short barreled rifles and shotguns(SBR and SBS). Machine guns manufactured before May 1986 can be transferred to civilians through the ATF buy paying another tax ($200 tax stamp).
Many states allow the civilian ownership and use of suppressors. Some even allow for suppressor use while hunting.
Post 1986 machine guns are called dealer samples, and can only be sold to law enforcement or military. Dealer are allowed to purchase for demo purposes. The rules for this have changed over time, and newly manufactured machine guns can be purchased only with a letter from an agency requesting the demo.
I would contact class 3 dealer in Minnesota to get the current legal situation in Minnesota. Last I heard, things were up for a vote to restrict your rights.