Sam1911
Moderator Emeritus
don't forget if you go the NFA route that you will have to notify the BATFE and get their permission if you plan on going out of state with the NFA firearm for a hunt.
Another point to consider is that some states prohibit posession of SBRs and SBSs. Would they have a problem with your gun --registered as an SBR, if it was only in true pistol or rifle configuration while it was in the state? I don't know. The strictest interpretation would say that your gun's status is now as a SBR, and thus prohibited, regardless of current physical configuration.
-Sam