Originally Posted by MacCool

What I would do is go ahead and register the lower receiver as an SBR per ATF. Assemble an SBR upper in barrel length of choice. Run a can, or not...I wouldn't be concerned about a suppressor on an SBR..they're not that hard on a quality device like the AAC. Then, I'd also get a 16" plus upper for the SBR receiver and if I were going out of the state and didn't want to do a form 5320.20, I'd just slap the long-barrel upper on the lower, screw the suppressor on it and go on out of town (making sure not to "retain control" of the short-barrel upper - IOW don't take it with you).

The suppressor is registered separately as a stand-alone item. It's not part of any particular firearm so it can be interchanged between rifles at will with no illegalities. Long barrel, short barrel, multiple rifles...whatever. All legal.

The receiver might be registered as an SBR, but if it has a long-barrel upper on it, it's removed from ATF purview (no longer an NFA item) as long as you don't "retain control" of the short-barrel upper. The phrase "retain control" is a little fuzzy, but the ATF interprets it to mean in proximity to the gun such that it can be installed right away. And, of course, there's the practicality issue. You're not going to accidently bump into an ATF agent who would then run your rifle's serial number. He'd have no reason to. As to local law enforcement, it depends on the state, but states that don't specifically state that the SBR has to be NFA-registered removes it from the jurisdiction of non-Federal law enforcement.


/