Two things at a minimum that you'll have to address if you determine that you can bring your ARs into MA (not an easy thing to figure out). You will have to pin your adjustable stocks (which a MA dealer has to do when you purchase one in state - if that's still possible), and you have to determine if your muzzle device is legal, and if so, pin that also. As a great example of the complete lack of understanding of firearms among the people who write these gun control laws, a standard GI flash suppressor is illegal, but a pinned compensator, like the BCM comp, is legal.