Good news/ Bad news.
Good news- Arizona does not restrict NFA (National Firearms Act) guns, so long as they are properly registered with the Federal BATFE.
Bad news- No fully automatic firearm- in ANY state- that was made after May 1986 can be transferred to a private citizen. Ones made and registered after that date can only be transferred to a machine gun dealer, or to a govt agency.
Assuming you can find one that was already registered, you apply to the BATFE for transfer. Application, prints, photo, approval by local Chief LEO, and a $200 tax payment. Wait several months. Rifle will cost you several thousand dollars.