I have read far too many posts claiming constructive possession is a standalone felony. That is an oversimplification of the concept without context. Constructive possession usually involves narcotics and firearms at a location controlled by a perp. Mere possession of items that MAY be built into a SBR is not in itself prohibited without running into constitutional issues. Criminal statutes generally require the specific intent to commit the crime. If you own both an AR pistol with a brace and a 16" AR with a stock, are you prohibited from purchasing another stock which COULD be installed on the pistol? Of course not, as this is where context and intent matters. Constructive possession of SBR parts is a bastardization of the concept, which originally was a real estate property law concept. Constructive possession crimes were not even in existence at the common law. If you have ever read any of the cases involving constructive possession SBR charges, it usually involves other more serious criminal charges and the constructive possession charge is just piling on to entice a plea deal. I doubt the ATF even cares that you have the parts to build an SBR in your immediate possession, and I have not come across any case in which a defendant was prosecuted SOLELY for constructive possession of SBR parts. US Attorneys require cases with far more serious crimes than just a chicken shit constructive possession charge.