Machine gun parts legality

This ‘funny’ came across in my Facebook feed. It’s a picture of a handful of M-16 automatic sears, and the caption reads ‘Found a bunch of these Mousetrap parts in my crazy uncle’s garage by his drill press…’

I remember back in the '80s you could buy these, and other parts, to illegally convert a semi-automatic AR-15 into a fully-automatic rifle, out of Shotgun News. Heck, you could even buy whole machine gun kits that lacked only the receivers (which are ‘banned’ under the 1934 National Firearms Act) with instructions/blueprints on how to build a functioning – and illegal – receiver. IIRC, no automatic firearms built after 1986 may be transferred (through the legal process) to civilians.

To convert an AR-15 into an M-16 you need an M-16 hammer, trigger, disconnector, selector, automatic sear, and bolt carrier. The automatic sear will not it into a semiautomatic receiver, but you could buy ‘drop-in’ automatic sears. I recall that ‘drop-in’ sears became registrable as ‘machine guns’ in and of themselves if purchased after a certain date. I think they’re completely banned now.

But what about the other parts? Let’s say you put M-16 parts into an AR-15 except for the/an automatic sear (and as I said, the ones in the meme won’t fit anyway) and the selector. (Using an AR-15 selector, you could not switch to AUTO so there would be no way to fire more than one round per trigger pull.) The resulting rifle would be semiautomatic, and could not be made to fire automatically. Would those parts be legal in that situation? Or have they been banned like the ‘drop-in’ sears? If ‘any machine gun part’ is illegal, does that mean ‘any’? Barrels? Forearms? Butt stocks?

NB: I am not planning, and have no intention to, do this. It’s just a question that I thought of when I saw the meme.

IANAL, but my understanding of it is that a drop-in auto-sear is legal as long as it was manufactured prior to 1981 and it has been NFA registered. New production is completely prohibited (per the NFA) and merely possessing an unregistered auto-sear is a felony. It doesn’t matter if it’s tucked in a box somewhere in the attic and isn’t actually a part of any working firearm, and it doesn’t matter if it was part of a big pile of junk that you inherited from your uncle. If you possess it, it’s a felony.

That depends on the part. If the part has no other purpose than to convert a semi-auto into a full-auto weapon, then that part is also prohibited.

Unfortunately, the current ATF under Biden has a proven history of being a bit “creative” in how they interpret things, to the point where the courts have had to step in and forcibly limit what the ATF can and cannot do. You could write to the ATF and get clarification if something like a non-functional selector switch would be banned or not, but the ATF could easily change their mind on a whim a couple of years later and then charge you with a felony for your selector switch even if they already sent you a letter saying that it’s legal.

Since the ATF doesn’t even follow their own rules, a straightforward factual answer isn’t really possible. The factual answer is that if the part is solely used for the purpose of making the weapon full-auto, then it’s prohibited. So a selector switch that has no automatic function should be legal. But the practical answer is that with the current ATF, you still could very easily end up being charged and convicted of a felony. Any further discussion on that takes us right out of FQ territory though.

The same barrel can be used on both full-auto and semi-auto rifles. Same with butt stocks, etc. It’s only the parts that are used solely on the full-auto versions that are banned.

Moderator Note

Let’s make sure to keep this discussion purely on the legal side of things. Any “how-to” information on exactly how to make a full-auto sear or how/where to obtain one is strictly prohibited in this thread. As with all things involving legal issues, you are free to ask what is legal and what is not.

Also, discussions about how the ATF is doing its thing are most likely going to be a political discussion. You can cite ATF rulings and such, but any discussion of gun politics is a P&E topic (or possibly the Pit, depending on your view).

It’s “any unregistered machine gun is illegal”, not any machine gun part. Each weapon, machine gun or not, has a part that contains the serial number and is considered “the gun”. A real M-16 receiver is the part with the serial number. A “drop in auto sear” is the part with the serial number. The link in an M1 carbine that makes it into an M2 full auto carbine has the serial number.

There was also an aftermarket part for AR15s that is called a “lightning link” that converts any AR15 into a machine gun. Only the very few that were stamped with a number and registered before 1981 are legal to own.

If your legally owned drop in auto sear or lightning link wears out, you cannot replace it. You can do everything you can to salvage it but only that original piece of metal can be used.

Oh, and you can still buy the parts kits because the critical part is either missing or cut up into approved pieces.

never mind

If it does not, then the gun/gun part was probably manufactured illegally according to Federal law, as taxes were not paid, they were not licensed or registered, etc.

A drop in auto sear (DIAS) is a machinegun. They are no more legal or illegal than any other machinegun you come across. IOW, things like date and place of manufacture, NFA registry, etc., are factors in whether you can own it. Just like any other machinegun. That is because it meets one of the 26 U.S.C 5845(b) definitions of a machinegun: it is "designed and intended solely and exclusively… and intended for use in converting a weapon into a machinegun

The sears in that photo are not machineguns. That is because they are not designed to convert a weapon into a machinegun. They are designed to make a machinegun work properly. They also cannot readily convert an AR-15 into a machinegun. So, simply possessing one is not illegal. You can easily and legally purchase them online if you want.

It mainly comes down to your receiver. If it is milled or drilled in such a way as to accept M-16 trigger components, you have a machinegun. Other than that, you can cram whatever you want in there and be legal. It’s not going to make anything shoot full auto–which is the whole reason it’s not illegal. The sear will not. But most of the other stuff will.

It’s not “any machine gun part”. A machinegun is defined as:
• Any weapon that shoots more than one round per pull of the trigger (or can can be readily restored/converted to do so
• The frame or receiver of any such weapon
• any part designed solely for converting a weapon to a machinegun (not a machinegun part, which is designed to make a machinegun a machinegun rather than convert a semiauto into a machinegun, like the DIAS)
• any combination of parts that can be readily assembled into a machinegun

A trigger, disconnect, sear, hammer and BCG will not make a regular AR-15 receiver into a machinegun, so you can buy those parts and possess them. nbd

That was meant to say “the sear will not fit, but most of the other stuff will.”

In a recent conversation some guy was going on about “ghost guns”, however you want to interpret that, presumably making guns yourself from raw materials/parts. So, presumably, the OP’s M-16 sears are legally OK but the receivers are not (unless carefully registered etc.)?

Reminds me of that documentary about gunsmiths in the Khyber Pass, who will produce you a knockoff of anything, quality varying from as good as a factory-produced example to you definitely do not want to actually fire it.

Correct. At least IAW Federal Law and Florida law. It’s possible (even likely) that they are illegal somewhere in the States. And the thing about the registry, is that it’s closed. It’s been closed for more than 3 decades, now. Every machinegun that is registered and ownable by a non-licensed person is already out there in circulation. All that can happen now is transfer of ownership. It’s why their value keeps going up, and why adding a couple machineguns to your investment holdings is not a bad idea. Plus, when society collapses, you’ll be able to get a lot more food having a machinegun than hordes of gold laying around. Best part is, unlike gold, you still keep your machinegun at the end of the transaction. Anyway, every time ownership of a machinegun changes, the new owner pays a $200 tax to the government, and they get a tax stamp (a real stamp) on their Form 4 (basically, the gun’s registration paper).
If you want something new, it can’t be registered. The only way to legally possess it is to become a licensed dealer or manufacturer of machineguns. I say “possess” rather than “own”, because for all the newest stuff, you would have to get rid of the machineguns when you closed your business and stopped renewing your license. There is a rare breed of dealer guns in limbo called, pre-samples (also pre-May samples), but just like the registered machineguns, the supply of those is finite. Those are little special because you can only buy them if you are a dealer, but once you close your shop and no longer have a license, you can still own it. You can only sell it to a current dealer or law enforcement agency, though.