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View Full Version : Legality of modifying AR15 into internal M16 dimensions


Dogmeat
04-17-2011, 5:27 PM
As an introduction, I have been reading on this site for about 6 months. I have learned a great deal about the technical details of firearms, what is available in California, and the fight to restore gun rights. This has influenced me to be part of this as a new gun enthusiast.

I wanted to tap into hivemind on this topic, as most answers were inconclusive. I have no intent to violate the law, as I do not even own a rifle. This is purely informational.

Here goes the full question.

Is it legal to mill an 80% lower receiver or an owned AR15 lower into the internal dimensions of an M16?

I am aware that some manufactures have high shelfs and low shelfs in their lowers for a registered DIAS; however, I also understand that drilling the hole for an M16 auto-sear constitutes manufacture of a machine gun.

What would be the best answer?

edwardm
04-17-2011, 6:08 PM
I will not, at this time, opine on the legalities. Not because my answer would be "I don't know", but because I personally figure it would be irrelevant.

My feeling is why invite added scrutiny or complications when it is not necessary to do so? This is akin to those folks that want a 3rd position mark and safety that moves to that 3rd mark on a semi-auto AR-pattern OLL.

While it's not as obvious a 'flag', why invite the potential extra pain of explanation (and attorney bills) when an OLL AR-pattern is cheap, easy and fun as-is?

As an introduction, I have been reading on this site for about 6 months. I have learned a great deal about the technical details of firearms, what is available in California, and the fight to restore gun rights. This has influenced me to be part of this as a new gun enthusiast.

I wanted to tap into hivemind on this topic, as most answers were inconclusive. I have no intent to violate the law, as I do not even own a rifle. This is purely informational.

Here goes the full question.

Is it legal to mill an 80% lower receiver or an owned AR15 lower into the internal dimensions of an M16?

I am aware that some manufactures have high shelfs and low shelfs in their lowers for a registered DIAS; however, I also understand that drilling the hole for an M16 auto-sear constitutes manufacture of a machine gun.

What would be the best answer?

pointedstick
04-17-2011, 6:10 PM
This seems like it can only end in tears.

badicedog
04-17-2011, 6:44 PM
Why do it? Crap like this will only fuel legislation to ban 80% builds. We already encountered a few 80% lowers that ended up in the hands of gangs back a few months ago in the Fresno area IIRC. This thread = FAIL

Kharn
04-17-2011, 6:45 PM
Technically only the autosear hole is prohibited, but I would not deviate from the AR15 blueprint showing the 7/16" (iirc) gap above the selector.

Dogmeat
04-17-2011, 6:45 PM
I feel like the fool. Here is an ATF document that should clear it up, and for anyone else who stumbles across this post.



Cite as FFL newsletter, Summer Issue 1988, Bureau of Alcohol,
Tobacco and Firearms, page 2, Washington, D.C.

REGISTERED MACHINEGUN CONVERSION KITS

Prior to the effective date of Public Law 99-308, thousands of
machineguns were registered by manufacturers on Forms 2 in
anticipation of the pending legislation. A this time, approximately
16,000 of these registrations have been identified as combinations
of parts to convert semiautomatic rifles into machineguns, rather
than machinegun receivers.

Several months ago, our National Firearms Act Branch became aware
that many of the conversion kits that had been registered were not
capable of converting a rifle without the receiver being modified
by drilling and/or milling operations. Modifying a semiautomatic
receiver in this manner constitutes manufacturing a machinegun
receiver, and such manufacture is prohibited as of May 19, 1986
(except for government use or export). It was evident that what
some manufacturers had registered as conversion kits, were in fact,
just parts, not machineguns, and therefore not subject to
registration.

To determine which registrations should be accepted as machineguns,
teams made up of an ATF inspector, special agent and firearms
specialist, visited most of the Class II manufacturers to determine
whether the items reported as manufactured should be registered.

The NFA Branch is now in the process of writing to the registrants
advising them of which items can remain registered and which will
be removed from registration.

Since a number of the parts kits have already been installed in
rifles by modifying the receiver, and are now possessed by
individuals as well as manufacturers or Class III dealers, a
determination must be made as to the status of these registrations.
We realize that some persons acquired these firearms in good faith
and there may be circumstances where we will continue these
registrations. The NFA Branch will review each of these
registrations after the registrant has submitted a signed statement
providing the details surrounding the acquisition of the firearms.
A final decision will be made on a case-by-case basis.

Please direct your questions to the NFA Branch; 202/566-7371 or the
Firearms Technology Branch: 202/566-7131

Ding126
04-17-2011, 6:47 PM
My 1st though is Why?

Dogmeat
04-17-2011, 6:50 PM
Although, I would add, that some of my ambiguous reading did indicate that the early AR-15's did have all of the matching specifications as the M16, just absent the auto-sear hole.

I'll add that I am only investigating what is approved/ sanctioned/ whatever you want to call it. The possibilities. However, I'm reminded of postings by oaklander on those bumpfire stocks. Perception to a jury matters.

supersonic
04-17-2011, 7:03 PM
There are a few lower receivers still being made today, by reputable companies, that have M-16 inner dimensions. No sear block, low shelf, and right side inner wall is identical to the left inner wall. A few just have the first two features, but have a thicker wall machined to the right. However, none, of course, have the dreaded "3rd input.";)

EDIT: actually, "sear blocks" are really quite rare now.

ke6guj
04-17-2011, 7:04 PM
I feel like the fool. Here is an ATF document that should clear it up, and for anyone else who stumbles across this post.



Cite as FFL newsletter, Summer Issue 1988, Bureau of Alcohol,
Tobacco and Firearms, page 2, Washington, D.C.

REGISTERED MACHINEGUN CONVERSION KITS

Prior to the effective date of Public Law 99-308, thousands of
machineguns were registered by manufacturers on Forms 2 in
anticipation of the pending legislation. A this time, approximately
16,000 of these registrations have been identified as combinations
of parts to convert semiautomatic rifles into machineguns, rather
than machinegun receivers.

Several months ago, our National Firearms Act Branch became aware
that many of the conversion kits that had been registered were not
capable of converting a rifle without the receiver being modified
by drilling and/or milling operations. Modifying a semiautomatic
receiver in this manner constitutes manufacturing a machinegun
receiver, and such manufacture is prohibited as of May 19, 1986
(except for government use or export). It was evident that what
some manufacturers had registered as conversion kits, were in fact,
just parts, not machineguns, and therefore not subject to
registration.

To determine which registrations should be accepted as machineguns,
teams made up of an ATF inspector, special agent and firearms
specialist, visited most of the Class II manufacturers to determine
whether the items reported as manufactured should be registered.

The NFA Branch is now in the process of writing to the registrants
advising them of which items can remain registered and which will
be removed from registration.

Since a number of the parts kits have already been installed in
rifles by modifying the receiver, and are now possessed by
individuals as well as manufacturers or Class III dealers, a
determination must be made as to the status of these registrations.
We realize that some persons acquired these firearms in good faith
and there may be circumstances where we will continue these
registrations. The NFA Branch will review each of these
registrations after the registrant has submitted a signed statement
providing the details surrounding the acquisition of the firearms.
A final decision will be made on a case-by-case basis.

Please direct your questions to the NFA Branch; 202/566-7371 or the
Firearms Technology Branch: 202/566-7131

I don't think this is refering to what you think it does. What happened in that many 02SOTs regisstered anything they could get their hands on before the May 1986 deadline. stock M16 and AK sears got regsistered as MGs. But in order to use that sear, you would have to drill the autosear hole in the semi-auto receiver, making that receiver identical to that of an M-16 receiver, not that you can't remove the auto-sear denial bump on an AR-15. This letter was not talking about merely removing that bump without drilling the autosear hole.

mhho
04-17-2011, 7:15 PM
Google is your friend in this case. This info has been out since 2004:

http://www.quarterbore.com/nfa/registeredreceiver.htm

http://www.quarterbore.com/nfa/dias.html

Dogmeat
04-17-2011, 8:49 PM
Thank you mhho. I am familiar with the quarterbore website. Looking through those pages again, I think this nugget from it should be a sufficent answer.

In this case, when the individual received their approved Form 1 they decided to convert the receiver to full auto by adding this DIAS as opposed to milling and drilling the lower and adding the more traditional GI Auto Sear that most people used to create a Registered Receivers.

FatalKitty
04-17-2011, 9:18 PM
There are a few lower receivers still being made today, by reputable companies, that have M-16 inner dimensions. No sear block, low shelf, and right side inner wall is identical to the left inner wall. A few just have the first two features, but have a thicker wall machined to the right. However, none, of course, have the dreaded "3rd input.";)

EDIT: actually, "sear blocks" are really quite rare now.

my Mega seams to be identical both left and right side... ??

Dogmeat
04-17-2011, 9:46 PM
Thank you as well, supersonic. I do wonder about that thicker right wall, which is, along with the sear hole, why a sear cannot fit in a lower receiver.

I see that as different than just having a lower shelf in some of the modern AR's. But that may still beg the question, if you say that some manufactures have matching walls, I assume they are thinner, is machining the receiver illegal?

I'm sorry if some of the comments reflect concerns among the people, and I appreciate the wisdom of those willing to share. I just find the technical details of interest to me, and reading endlessly wasn't answering my questions.

I'll leave it to the moderators to delete if they find that the discussion is not serving the purpose of the board.

Dogmeat
04-17-2011, 10:07 PM
ke6guj,
Didn't want to forget about your response. The denial bump that you are referring to is the sear block, correct? I know that the ATF has stated that it can be removed, but that still doesn't answer the question about the receiver walls.

From my reading of the document, with the "drilling and/ or milling" language, we know that drilling the sear hole in the receiver is making a machinegun; but is milling the dimensions of receiver thinner, which could accomadate a sear, a conversion of the receiver?

Just wanted to add, I don't want anyone to take my questioning as aggressive or attacking. Just more like follow-up questions.

ke6guj
04-17-2011, 10:37 PM
I was referrign to the sidewall bump of the reciever wall to block a factory sear, not the sear block that colt installed to block DIASes.

supersonic
04-18-2011, 7:21 AM
my Mega seams to be identical both left and right side... ??

Then what does that tell you?

FeuerFrei
04-18-2011, 10:21 AM
As an introduction, I have been reading on this site for about 6 months. I have learned a great deal about the technical details of firearms, what is available in California, and the fight to restore gun rights. This has influenced me to be part of this as a new gun enthusiast.

I wanted to tap into hivemind on this topic, as most answers were inconclusive. I have no intent to violate the law, as I do not even own a rifle. This is purely informational.

Here goes the full question.

Is it legal to mill an 80% lower receiver or an owned AR15 lower into the internal dimensions of an M16?

I am aware that some manufactures have high shelfs and low shelfs in their lowers for a registered DIAS; however, I also understand that drilling the hole for an M16 auto-sear constitutes manufacture of a machine gun.

What would be the best answer?

You are milling an 80% to M16 dimensions?
Then you are copying what other OLL manufacturers are doing with 100% lowers.
It smells legal to me.
Remember.....
The third hole is verboten! Auto sear is verboten!
All NFA rules apply.......... bow to the man.

supersonic
04-18-2011, 10:51 AM
Remember.....
The third hole is verboten!

Depends on who you are "dealing" with.:p

cmaynes
04-18-2011, 11:13 AM
modding a perfectly functional semi auto receiver to one "close" to a regulated one seems like a really STUPID thing to do in my opinion....

It just begs (loudly) the constructive possession dogpile when it is not needed.

tommyid1
04-18-2011, 11:17 AM
For informational purposes. Yes you can do anything you want to the lower sans the 3rd hole. But what for? If you are planning on somehow obtaining the parts and converting something just do it and don't talk about it. No sense in incriminating yourself. And allways remember these three words... don't get caught. But seriously don't do it lol

Sent from my Droid using Tapatalk

12voltguy
04-18-2011, 11:22 AM
For informational purposes. Yes you can do anything you want to the lower sans the 3rd hole. But what for? If you are planning on somehow obtaining the parts and converting something just do it and don't talk about it. No sense in incriminating yourself. And allways remember these three words... don't get caught. But seriously don't do it lol

Sent from my Droid using Tapatalk

:cuss::rofl2::rofl2:

FatalKitty
04-18-2011, 2:53 PM
Then what does that tell you?

tells me that if FA ever becomes legal (HAHAHAAHAHAHAHA) I'm good to go?

CHS
04-18-2011, 3:28 PM
Plum Crazy lowers come from the factory with M16 interior receiver dimensions all the way back to the rear upper receiver lug area.

supersonic
04-19-2011, 6:42 AM
modding a perfectly functional semi auto receiver to one "close" to a regulated one seems like a really STUPID thing to do in my opinion....

It just begs (loudly) the constructive possession dogpile when it is not needed.

The OP wasn't asking for anyone's 'opinion' on anything. Just simple information/facts, that's all. Nothing more, nothing less.

cmaynes
04-19-2011, 8:31 AM
The OP wasn't asking for anyone's 'opinion' on anything. Just simple information/facts, that's all. Nothing more, nothing less.

and that answer was given quite early in the thread. Other opinions on the sensibility of modifying a commercial lower were given as well- this board is full of opinions-

Dogmeat
04-19-2011, 9:46 AM
Plum Crazy lowers come from the factory with M16 interior receiver dimensions all the way back to the rear upper receiver lug area.

Thats very interesting, and they sell to public and law enforcement.

Dogmeat
04-19-2011, 9:52 AM
I try to give people the benefit of the doubt, since it is the internet, and not having met any of you. I just go on the premise that you are all great guys. So I don't take offense when someone wants to express their opinion and I note it, although I am really just looking for the facts and if you have any links with supporting documents.

Dogmeat
04-19-2011, 10:07 AM
You are milling an 80% to M16 dimensions?
Then you are copying what other OLL manufacturers are doing with 100% lowers.
It smells legal to me.
Remember.....
The third hole is verboten! Auto sear is verboten!
All NFA rules apply.......... bow to the man.

I could ask, and I'm sure it is an old regulation or court case, but where does it say that having the sear hole is prohibited? I come across this statement, but I never see the supporting document ever linked.

Dogmeat
04-19-2011, 10:13 AM
For informational purposes. Yes you can do anything you want to the lower sans the 3rd hole. But what for? If you are planning on somehow obtaining the parts and converting something just do it and don't talk about it. No sense in incriminating yourself. And allways remember these three words... don't get caught. But seriously don't do it lol

Sent from my Droid using Tapatalk

Never crossed my mind. More interested in form and function. Although I do admit there is a beauty in the genius of the mechanics of auto guns.

I think I may start reading up on NFA more thoroughly.

Dogmeat
04-19-2011, 10:16 AM
This all started after reading about how the receivers are machined industrially, advice to home builders, and realized the differences in the internal dimensions. It made me wonder about those in the market for the Retro builds, who want to further accomplish the asthetic look inside and outside.

CHS
04-19-2011, 2:31 PM
I could ask, and I'm sure it is an old regulation or court case, but where does it say that having the sear hole is prohibited? I come across this statement, but I never see the supporting document ever linked.

Having the sear hole would make it an M16 receiver, not an AR15 receiver. That would be a federal felony. Period.

While you may have the interior dimensions of the M16, without the sear hole you still can't install the necessary auto-sear. Once you drill that hole, it's no longer a semi-auto receiver by ANY definition of the word.

Why on earth would you think that having the sear hole would be allowed?

The "supporting" documents are the 1934 NFA, 1968 GCA, and the 1986 FOPA.

Dogmeat
04-19-2011, 10:08 PM
Thank you bdsmchs,
I would never think that having a sear hole would ever be allowed. I suppose I was not putting all of the key ideas together. I have read the three documents that you sited, but they didn't define the 'qualities' of the receivers that made them machine guns when I read them before. I suppose I just needed to be led by the nose a little bit.