[Theohazard]

You can't always be sure the person on the phone knows what they're talking about. If they tell you that you can't take it interstate without approval even if the parts are disassembled and sufficiently far apart, they're wrong.

It's very clear according to the guidelines set forth by federal law and ATF rulings and regulations: An SBR is not an SBR if it's not in SBR configuration. So as long as you avoid any constructive possession issues (see 2011-4), you can take it interstate like a normal Title I firearm.

Now, the only issue I could see would be when you were in your new state and got the approved 5320.20 back: Technically that form would be incorrect since you didn't actually transport an SBR across state lines: You transported a receiver across state lines and a short upper that was completely separate. Also, I could see them having an issue with the Form 5320.20 being retroactive since it would end up getting approved after the move dates you put on the form.

That said, the ATF agent I dealt with was well-versed in the NFA and he didn't have any problem with it. In my experience when it comes to issues like the details of the info you put on the 5320.20, the ATF tends to be a little flexible as long as you're doing your best to comply. I mean, who can be 100% sure of the exact amount of time it will take to drive across the county? I know I couldn't: My transport dates on my form ended up being off thanks to situations beyond my control.