But if you've got that, you can build at the very least, a submachine gun, from scratch. (Or use existing barrels and do the rest from scratch, which would make it even easier).
Bottom line, the prohibitions on full auto weaponry are just as unconstittutional as other gun control. Under the so called (and bogus) Supreme Court "Miller" test, they are probably even more so that those banning so called "Saturday Night Specials".
With respect to the laws, you will find that I am in no way in agreement with infringement of the second amendment, in any way. I believe the citizenry should be able to access the same weapons that the us infantry soldier has access to. The responsibility for safe use lies with the owner of said firearm. Misuse, causing harm to innocents, should be dealt with severely, to the offending person, not to all users or owners of same or similar firearms.