well the proof that you did not buy it outside the country is when custom's sees it on your 4457 form with the serial number and mfg. name on it. I would not hesitate taking mine again
You would think that would be sufficient. You own it, you took it. Shouldn’t be a problem … until it is.
Some Class III devices require that you get government permits just to travel to certain states. SBR’s in particular (Not sure about cans and different states) Taking it out of the country is asking for scrutiny, if not fines or confiscation (even if temporary). All you need is a CBP agent who wants to impress a supervisor (had it happen before) to completely screw your day.
I don’t know the law, so, you may be 100% correct. But I’m not risking my can on the word of some ill informed gov official who doesn’t even know what a tax stamp is.
