crossedcannons,
that's my understanding as well. as far as the carbines go, a receiver that's stamped or over stamped M2 is a machine gun; a receiver or any other part that's registered is a machine gun; and if all 7 of the sacred parts, whether any of them are registered or not, are together in the same place at the same time ATF considers that a machine gun. but anything besides the actual registered part can be replaced.
i've been told and read that these guns were never built for full auto and i shouldn't try and put 1000's of rounds through them like i do with my mac's. that's why i've been looking for a registered trigger "kit". also, i don't want to be the guy that destroyed or wore out a rare M2 just to have fun playing with it on full auto. am i worried about something i shouldn't be?
thanks,
frank