You bring up a good point, however, in that even when certain weapons are not commonly available, there is still nothing to stop criminals from illegally fabricating them.
True but it is such a rarity. There is a much greater chance of hitting the lottery than seeing one of those. As I have pointed out before full auto weapons are horrible for use in committing crimes, mass shootings or most other events that antis think they would be useful. In truth they have limited but useful application on the battlefield. In the NHS they may have saved lives.