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.
Maybe - or, just enlist. Choose combat arms, and you get to eat, sleep, bathe, and otherwise live with your new automatic spouse.
Another method would be to train, become an LEO, and have those responsible in your jurisdiction simply get them from Uncle Sam and issue it to you.
I shot my issue M16, M16A1, and M16A2 for 22 years, had a lot of fun with it. I also got to shoot the M60, M249, M2, and Mk17. Likely there will be a bit less live fire for familiarization floating around in the future, when I was in a Reserve MP unit, we fired twice annually, and active duty four times a year.
Go MP, when you get out, finish up with Police Academy, and you get full auto for life, it seems. Fair? Too bad, it's the law.
I really don't care about the inequity - I don't have to feed, safeguard, and protect it now. It gets old.