Leverdude is right. they are manufactured as pistols because if they were rifles they would be an SBR which would mean having to get a tax stamp from the BATF to own. by making them new and classifying them as pistols, they are exempt from this and anyone can buy them without a stamp and fee to the BATF. i don't think you can legally put a longer barrel or stock on them either. because they are classified as pistols. same legal rule as you can't take a M94 rifle and legally make a Mare's Leg out it because then it's an SBR.