If legality is no longer an issue it would seem wasteful to bother converting semis to full unless you're just dropping in a selector switch. Why not just gather from the source? That's the usual source of supply for any budding insurgency.
Well, you have a good point, but for the record I have no plans to ever buy one, steal one nor illegally convert one, as even in the direst chaos, I would rather use ammo sparingly and accurately.
HKs are pretty easy, from what I hear. Same with uzi.