Since you mention the machine gun ban, I guess you mean the 1986 Firearms Owners Protection Act? Actually the machine gun ban was about the only bad provision of that act, which removed many of the more abused provisions of the 1968 Gun Control Act (and earlier gun laws as well) and attempted to reign in the BATF. See Hardy. It was a last minute amendment on the floor by Congressman William Hughes of New Jersey, and engendered no debate until the bill went to the Senate, and even that was generally in the nature the "it doesn't change anything", even though the intent of the amendment's author was to do just what has been done, that is to ban new production of machine guns for the civilian market. Why? Because he could. No trigger is required for gun grabbers, although they will make use of various incidents to further their agenda, which is always there.
Thanks for the Hardy link.