In 1934, a law was passed regulating the ownership of certain types of weapons: short-barreled rifles and shotguns, machine guns, "silencers," "destructive devices," and "Any Other Weapon." In 1938, the Supreme Court ruled in United States v. Miller that Congress had the right to do so, as the Second Amendment existed so that citizens could acquire privately-owned weapons for militia use, and the weapons that were regulated by the NFA were, for the most part, not military weapons at the time. That will be my primary reason as to why the various parts of the NFA are obsolete, as I go through the list of weapon types regulated. The secondary reason will be advances in arms technology (if new communication technology such as television, radio, telegraph, telephone, the internet, typewriters, automatic printing presses, fountain pens, ballpoint pens, or mail delivery by automobile are protected by the First Amendment, then new weapon technology is protected by the Second) This diary post will not discuss what should or should not be regulated. I will also not be discussing the ways that NFA weapons can be acquired legally. This is not an opinion piece, it is solely intended to be informative.
1. Short-barreled shotgun:
The Miller case was specifically about short-barreled shotgun, meaning shotguns with barrels shorter than eighteen inches. When US military personnel use shotguns, they tend to have fourteen- or sixteen-inch barrels.
2. Short-barreled rifle:
Originally, the NFA required rifles to be at least eighteen inches long. Some time after the Second World War and the Korean War, when the government realized that several hundred thousand non-military, non-police individuals possessed surplus M1 carbines without registration or a tax stamp, the NFA was changed so that 16" was the minimum requirement for a non-NFA weapon, as Miller clarified that the Second Amendment protected military-grade arms. Nowadays, the US Army uses the M4 carbine, which has a 14" barrel.
Also, due to the modularity of the AR-15, the most popular firearm in the United States (and what the M16 and M4 were designed from), it is possible to configure one as a pistol. An AR pistol would be one with a shorter barrel and a stock. If an AR owner decided to, without thinking, take the stock off of his AR rifle and put it onto his AR pistol, he would be guilty of a felony.
3. Machine gun:
This is an example of the general public perceiving an object as more dangerous than it actually is. Submachine guns were perceived as "gangster guns" in the 1930's, a term that had about as much substance as "assault weapon" does today. In actuality, automatic fire is significantly less effective at most roles than firing one shot at a time and aiming, and can often be only negligibly faster, or even slower than lever-action or semi-automatic firearms. In any case, Miller's requirement for the weapon to have a military use renders the NFA restrictions on machine guns obsolete. Since the 1940's, machine guns small enough to be "arms" and not "ordnance" (which the Second Amendment doesn't protect) have been standard equipment for military forces worldwide.
4. Silencers:
As with machine guns, these are an example of the general public perceiving something as more dangerous than it actually is (and oddly enough, they were invented by the son of the man who invented the machine gun: Hiram S. Maxim and Hiram P. Maxim). There's a reason why people who know anything about them call them "suppressors," not "silencers." They do not silence anything, unless special subsonic ammunition is used. For the most part, they just reduce the volume enough that the sound has to be sustained to cause hearing damage, instead of immediately causing hearing damage. They are essentially car mufflers that screw onto the end of a firearm barrel, and even with mufflers, the vast majority of car engines are not silent.
Although suppressors have never been standard-issue military equipment, they are often issued to snipers and light infantry forces like the US Army's 75th Ranger Regiment, and if ever the Unorganized Militia (federal and most state law considers all males of a certain age to be part of the "Unorganized Militia") was needed, their tactics would be similar, if they weren't guerrilla tactics such as those of the Viet Cong or the Taliban, as they would probably not have ordnance such as tanks and artillery to support them.
Also, the wording in the NFA is such that the Bureau of Alcohol, Tobacco, Firearms, and Explosives can and has declared brands of steel wool or equivalent pot scrubber things to be NFA-restricted due to their ability to dampen noise.
5. Destructive devices:
This is one big grey area.
Without an ATF-granted "sporting exemption," firearms of above .50 caliber are heavily restricted. However, the .950JDJ cartridge has that exemption and it has absolutely no sporting use. J.D. Jones specifically designed it so that it would demonstrate how ridiculous this requirement is. In addition, the sporting exemption is not necessary if the weapon must be disassembled in order to be reloaded, as is the case with the .700 WTF cartridge.
Poison gas weapons are considered to be destructive devices. They tend to be ordnance, and not arms, and so are not protected by the Second Amendment.
Explosive and incendiary weapons are also destructive devices. However, this can be applied rather arbitrarily, for example, signal flares aren't regulated at all, but if intentionally used on a human being, the user is in violation of the NFA. With regard to grenades and grenade launchers, the line between arms and ordnance is very hard to draw. The Mk. 19 grenade launcher definitely is ordnance, as it is a crew-served weapon usually found mounted on Humvees and armored vehicles, however, the M32 grenade launcher's status is much tougher to determine, being an individual weapon, as is the M203 mounted under the barrels of M16's and M4's.
6. Any Other Weapon:
Although these are generally not protected by Miller, this category is, for the most part, rendered obsolete by modern technology.
One example would be the Taurus Judge and Smith & Wesson Governor models of revolver. They are designed to shoot .410 bore shotgun shells, but the NFA requires them to be less effective than they could be. They aren't allowed to have smoothbore barrels like regular shotguns, as they would no longer fit the definition of "pistol" (a non-NFA type of firearm) and they're too small to be shotguns, so they're Any Other Weapon.
Another example, as with short-barreled rifles, is the AR-15 style of firearm (manufactured by Bushmaster, Colt, Armalite, Smith & Wesson, and pretty much everybody else). As mentioned before, it can be configured as a pistol. However, if it lacks a stock and a user decides to attach a vertical foregrip, that user is guilty of a felony. This applies to other pistols that have Picatinny rails for attaching flashlights and other such things, such as the Kel-Tec PLR-16, as well.
Images of some firearms and ammunition referenced in this diary:
M26 Modular Accessory Shotgun System (short-barreled bolt-action shotgun used by the US Armed Forces as either stand-alone or attached to a rifle below the barrel):
M1 Carbine:
AR-15 configured as rifle with vertical foregrip and optics attached via Picatinny rail and additional receiver above the rifle:
AR-15 configured as pistol with optic attached via Picatinny rail:
.950 JDJ cartridge in comparison with two-liter bottle of root beer (update: it's "only" 20oz):