You need what's called a Class 3 dealer's license. My stepdad has his FFL and basic dealers license, so he can buy at wholesale and sell to whoever or buy guns for his friends at cost. This license includes pistols, semi-auto rifles, shotguns, etc, pretty much everything. The Class 3 involves an ENORMOUS amount of time, paperwork, MONEY, and approval from several state government positions.
They're rare, but there are people who have them. If I were you, I'd look into Machine gun 'meets' or 'shoots' around your area. We have an annual one here in AZ called the Big Sandy Machine gun shoot.
http://www.mgshooters.com/ We try to go every year. AT said events, you can 'rent' other people's guns [if they let you] for x amount of money, you can shoot a few mags thru whatever is for rent. For example, I've shot an [automatics] browning m1919, thompson, sten gun, AK47, etc.
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