The difference between an M-16 and an AR-15 are the “6 magic parts”. In 1990’s having an AR-15 along with any of those magic parts was enough to get you charged with a felony under the “intent” to make a machine gun.

Those parts are:

1. Bolt Carrier
2. Hammer
3. Trigger
4. Disconnector
5. Selector
6. Auto sear

The seriously magic part is the auto sear. THis part catches a hook on the back of the hammer and holds the hammer back until the bolt has locked up. Only then does the auto sear allow the hammer to drop, firing the weapon.

The auto sear fits above the selector. The difference between an AR-15 and a “machine gun” is the hole in the lower receiver for the auto sear pin. It is no longer the 6 magic pieces.

In addition to the actual auto sear there are drop in auto sears. They are very hard to find today (legally) because they were dirt cheap prior to 1986 and nobody was going to pay the ATF $200 on a $30 part. Today a DIAS goes for north of $30K. M-16A1s are going for around $35k. A modern M-16 that is not transferable can be purchased for $500-$750 on the cheap side. A full auto lower parts kit runs about $80.

Regardless, DIAS are a thing. They are a machined part with specification tolerances similar to that of an AR-15.

But there is another way. A “Lighting Link” is a thin piece of metal or bent up coat hanger that is suppose to perform the same function as the auto sear or DIAS. Reports say it is not as reliable as the actual part but it does work.

A company in Wisconsin or Florida, it is not clear where the company is located, created a laser engraved sheet of thin metal which outlined all the parts required to make a lighting link. The end user would have to cut out the parts and file them to the line, assemble the parts and then maybe it would work.

This was obviously done to get around the NFA by claiming 1st amendment protection of the printed/engraved item.

This was done successfully in the 1980’s in regards to PGP. Pretty Good Privacy used strong encryption. Encryption algorithms were considered “arms” under the ITAR regulations. Thus the government block the publication of PGP because it would be exporting arms. The work around was simple, they printed the code on an OCR font then sent the printed, 1st amendment protected, document to a country in Europe where they turned it back into code. Thus everybody gained access to strong personal encryption.

In the case of Matthew Hoover of Wisconsin and Kristopher Ervin of Florida the ATF raided them and accused them of all sorts of nasty violations of the NFA. Matthew and Kristopher have been slowly losing their cases.

On July 1st, 2022 Mathew Hoover filed to have the case dismissed based on Second Amendment grounds. They are claiming that the NFA is unconstitutional.

The Government may attempt to argue that machineguns are beyond the scope of the Second Amendment by attempting to characterize them as “dangerous and unusual,” as it has in other cases, but this is not the test. The court’s invocation of “dangerous and unusual” weapons in Heller and subsequently Bruen was for the purpose of discussion of what might be a constitutionally acceptable law, rather than the endorsement of any particular extant policy. Bruen, 597 U.S. at *12 (Clarifying that the Court was not undertaking “an exhaustive historical analysis…of the full scope of the Second Amendment”) (quoting Heller, 554 U.S. at 627). Rather, the only way a court may conclude Defendant’s conduct falls outside the scope of the Second Amendment’s unqualified command remains clear: the Government must prove the particular regime in question is consistent with the history and tradition of the United States. Id at *15. Furthermore, the question of whether a weapon is “in common use at the time,” necessarily pins the analysis to the time before the prohibition. To consider otherwise would incentivize the Government to legislate wantonly and aggressively, seizing arms, then later evade constitutional scrutiny by suggesting that the arms cannot be in common use, because the Government prohibited them. Such circular logic would be inconsistent with any fundamental rights jurisprudence. Thus, the Government has the burden to prove that the regime in question is consistent with the history and tradition of firearms regulation in this country around the founding era.
— Machine Gun — USA v Matthew Hoover — Supplement to Motion to Dismiss070122

There will be more lawsuits against the NFA. This case might actually be strong enough given its first and second amendment defenses. It would not surprise me to see the courts dismiss this case on first amendment grounds, or the government, so that the NFA survives.

Edited: Fixed date from January 1st to July 1st