Where are you planning on moving to? I ask because (A) THAT ain't gonna happen in California. (B) Unless you are a law enforcement AGENCY, or an ARMY, it ain't gonna happen anywhere else in the US.
First, full auto firearms cannot be transferred to a private invidual unless they were already registered with the BATFE as of May 1986. Yeah, that means no NEW full autos. That IS a new gun, isn't it?
Second, the 12 inch version is a National Firearms Act weapon even if it a semi-auto. Called a Short Barreled Rifle. Requires transfer thru a class III dealer, registration with the BATFE before you can possess it, and paying them a $200 transfer tax. Also, see (A) above.
I REALLY do not mean to seem rude, or to dash cold water on the firearm you may lust for- but if what I posted above is new info to you, you should spend some time boning up on the laws that restrict what you can do. If you are already aware of those, and are perhaps a Class III Dealer, who can get a dealer sample, I abjectly apologize for the lecture.