It doesn't have to be ruled unconstitutional. It can be repealed by a simple majority of both chambers of Congress.
If you take it to SCOTUS and get rebuffed, you're screwed, possibly for eternity. But you can put progressively evolving versions of the bill before the Congress all day every day from now until eternity, or until one gets passed (and signed).
So SOCTUS IS NOT the preferred axis of advance for ridding ourselves of the NFA.
But what would be simpler (and is more likely) is to amend the list of NFA devices. Every device on the list is on it because gangsters using those devices made newspaper headlines during the Prohibition Era. Before 1935 you could legally buy a Tommy Gun or a Colt Monitor (select-fire civilian version of the Browning BAR) from a Sears & Roebuck catalog, or down at the local Ace Hardware. And there was never any great outcry to have them regulated before the Volstead Act.
The whole thing was a knee-jerk reaction, and bad news invariably makes worse law. The NFA always was and still is shit legislation. If they don't repeal it, they at least should remove the more innocuous devices from the NFA list.
There is absolutely no sound reasoning behind suppressors or short-barreled rifles or shotguns being controlled.
For one thing, all it takes to manufacture your own SBR or sawed-off shotgun is -- guess what? -- A SAW. All you need is a hacksaw to convert a legally-bought long gun into an illegal short one. And if they're creating it in order to commit a crime with it, it's absurd to conjecture they would balk at one more crime before creating the illegal firearm.
And the crazy bit about suppressors is that in some of the countries with the strictest gun laws, suppressors are uncontrolled, sold over the counter, and in fact it is ILLEGAL to fire a rifle without one. They quite logically find causing all rifles to make less noise a good thing.
And suppressors in those countries cost less then one-fifth of what they do in America, in large part because there's no gummint red tape, nor any potential legal jeopardy for mis-handling the gummint paperwork.
So the first step is to take the most ridiculous devices on the NFA list.
And since the NFA was signed into law, there have been exactly TWO (2) homicides in which a legally-posessed machinegun was used. In both cases the offender was a law enforcement officer. In one case it was a privately-owned weapon (memory is uncertain but IIRC it was either an Uzi or an Ingram) and in the other case the offender used a machinegun assigned to him by his police department.
So the NFA by itself is perfectly adequate for protecting the general public from Roland the Headless Thompson Gunner. But the Hughes amendment needs to be repealed because it was never needed in the first place. There still are (IIRC) a quarter of a million fully-automatic firearms owned by civilians, and they're invisible in crime statistics. The ANTI's passed Hughes for no other reason than they found themselves with the adequate political capital to do so, period.
But I don't see repealing it as a major obstacle, provided we can get a Republican back in the White House (which presumes we might some day have free and fair elections again), along with Republican majorities (with spines) in both chambers.
You’re right, especially about SBRs, SBSs and a saw. It is beyond ridiculous that you can be charged for “ constructive possession” if you have a barrel under 16 or 18 inches, even if it is not attached to a firearm. By that absurd logic having a hacksaw or portaband in your possession would leave you open to a constructive possession charge, since it would take more time to mount a replacement barrel than it would to saw off the existing legal length barrel. A portaband would take maybe 5 seconds to cut a shotgun barrel, 10 or 15 to cut a rifle barrel.
As to the homicides by legal MG owners, only one of the killers was a cop. The other was either a doctor or dentist, who used a .380 MAC. There is a copy of newspaper reporting on the murder floating around the net, haven’t seen it for years so details may be a bit fuzzy. As for the cop I have seen no reporting, but word of mouth info was that he killed an informant.