Between #3 and #4
US v Miller said (correctly) that the 2nd amendment protects weapons that support the function of a militia. Anything usable by a militia to attack legit military targets should be protected. So definitely anything an 11B is issued.
Strange case, that one.
As you may know, the Judge ruled in favor of Mr. Miller, the perp, knowing he wouldn't be sticking around for the appeal which was sure to follow.
All the Supreme Court heard was the gummint's side of the case since nobody wanted to pay his legal fees (where was the NRA in 1939?) so it was kinda like a FISA court passing judgement on the meaning of the Second Amendment, except this was a precedent which lower courts would be held to.
Since there was no counsel for the defense, the court didn't know (or the justices disregarded it if they did know) that sawed-off shotguns were also military weapons. They were issued to soldiers in WWI--then known as The World War--and should have been permitted for civilians under the "militia" clause of the Second Amendment.
Except the court ruled otherwise, and now we're ever so s-l-o-w-l-y getting back to the original intent of Amendment 2, but it won't happen overnight.