I don't believe the arm is a prohibited part but this s a grey area at best, I am sure lots of "legal experts" will jump in here and "correct" us! I think it better to play safe and dump them. For what it is worth, in my opinion, a gun is what it is, not what it may be registered as, no matter what the certificate might say. I have had the CFC make "Administrative corrections" when they want to. I have seen US M14 rifles at gun shows with the selector lug ground off and presented as "Rare semi auto M14 variants" but who am I to offer an opinion? there is always something new to learn every day, but my advice is to be very cautious with such animals.