I currently live in Utah (which is quite possibly the best gun state out there) but will most likely move in the next few years. I was looking and making an SBR for home defense but wondered if I moved to a state where they are illegal what would happen? Would I have to get rid of it? How does that work? I couldn’t find anything on this.
If you move some place where they aren’t permitted, but regular rifles are, then you would need to make it compliant for that state. So make it a non SBR. CA would be permanent barrel length of 16" or more and a bullet button to lock the magazine in place. Oh and it can’t be a named firearm in their ban list they made in the 90’s. Unsure of some of the other ban states.
Assuming your AR15 is legal in the state you move to, all you need to do is put a 16 inch barrel on it. That makes it a Title I, GCA non-SBR firearm and it is thus removed from the purview of the NFA. ATF suggests you notify them of the change, but it’s not required.
Or, just take the lower. Sell the short upper. Also safe to leave the short upper(s) in the current location if you have somewhere to store them or somebody that could use them.