Full auto MGs made before 1986, IIRC, could be bought in some states if you paid a tax, maybe $200.00, to the Feds. Someone correct me if I'm wrong, but I believe the Volkmer - McClure Act prohibited civilian purchases of new MGs after 1986.
The act prevented any new fully automatic weapons from being bought and sold in civilian hands if the weapon was first registered after 1986. If the weapon was first registered before 1986, it can still be legally bought, sold and possessed under federal law both now and in the future. (Of course, not all states allow these weapons, but that's another matter.)
So, in summary, I think that what you wrote about the law is correct.
Not quite. It prohibited further registration of "transferable" MGs, that is, those that can be possessed by non-licensees. MGs registered as transferable prior to 86 can still transferred.
You are absolutely correct, and from that point on, we the people have and will be at a technical disadvantage vis-a-vis those from whom the Constitution of the United States of America was designed to protect us. This egregious law should also be put to rest on the ash heap of history where it and the 1934 law belong. Now we just have to hold our breath and hope and pray the the usual does not take place just prior the the laws lapse.