An interesting aside to the M2 carbine discussions. I am now living in the states and was looking into getting an M2.
In order to legally own (other than dealers) an M2, you pay a $200.00 one time transfer tax, go through a record check, and if everything checks out, you get the firearm permit.
However, the M2 is one of the few firearms that I have been told you can possess without the permit under certain very strict circumstances.
As the M1, and M2's often had parts swapped back and forth during WW2, and the Korean war, there are apparently a number of M2's with the M2 receiver, and trigger group in civilian possession without permits.
However, there are I think 5 parts that if you even have in possession while you possess one of the M2 receivers, you are considered to have a machine gun..even if they are not installed. (Hammer, sear, selector, selector spring, and trigger I think are the parts.)
So as long as you don't have those parts, I have been told that you could have an M2 receiver in a shootable firearm...boy, I sure wouldn't want to try the legality of "someone told me" out in court though.