What makes an AR-15 shoot full auto?


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peck1234
May 31, 2008, 02:09 PM
Just wondering what part of an AR-15 will make it shoot on full auto? Is it a certain lower?, Bolt?

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Glockman17366
May 31, 2008, 02:18 PM
Just do a search on the web...
The AR-15 is a fine sporting rifle. Modifying a rifle or any other firearm is a federal offense (although I'm not sure of the constitutionalty of those laws).
The parts required won't fit in an unmodified semi-auto AR-15, to the best of my knowledge.

taliv
May 31, 2008, 02:22 PM
the hammer, bolt carrier, disconnector and selector switch are all different from the semi-auto parts, and there is another auto-sear doohickey in there.

theotherwaldo
May 31, 2008, 02:22 PM
Discussing this in public can get you some unwanted attention.

briansmithwins
May 31, 2008, 02:27 PM
About $15k to $17k, assuming your state allows it.

Can't do conversion unless you're a licensed manufacturer. Violations are a major Federal no-no, which are aggressively prosecuted.

BSW

MaterDei
May 31, 2008, 02:41 PM
The OP didn't suggest at all that he was wanting to illegally modify his existing semi-auto firearm. When we firearm enthusiasts make such a big deal about somebody curious about how a gun functions, we're not doing ourselves a favor.

Calm down people and if you don't know the answer to his legitimate question just move along.

/rant off

redneck2
May 31, 2008, 02:44 PM
So, I guess every time someone asks a question about Class III, they'd better expect a knock on the door....

oh CRAP....I just looked out the door.....here come the Feds...

:rolleyes:

peck1234
May 31, 2008, 02:44 PM
thanks MaterDei Just like to know how things work you know?

All beacause i like to see how nuclear bombs work and how there made doesent mean im going to make one! : )

nalioth
May 31, 2008, 02:50 PM
It is unfortunate we are where we are.

Answering the OPs question can prospectively land one in trouble.

I don't see any 'favors' being done or denied.

To the OP: As mentioned above, there are plenty of sites on the web which go into this.

Telperion
May 31, 2008, 02:51 PM
Here's a page that shows how the fire control group parts interact in a 3-round burst weapon. Similar principles apply for continuous full auto.

http://www.ar15.com/content/guides/function/burst/

DWARREN123
May 31, 2008, 02:56 PM
For a semi auto it is either wear and tear or bad gunsmithing. For a Class III it is the fire control system (trigger-sear so on).
It is illegal to mod a semi unless you have BATFE approval and signed off paperwork.

TexasRifleman
May 31, 2008, 03:14 PM
Ignoring the wailing and gnashing of teeth, it's a fairly straightforward answer.

The basic answer to your question is that yes, it's a special lower in most cases plus a few extra parts. There is an extra hole in full auto lowers for a pin to hold a sear that does not exist on the semi.

When the semi fires, the existing sear has a hook that holds the hammer back if the trigger is held down, stopping it from firing again until the trigger is released, or "reset".

This additional sear on the full autos releases the sear holding back the hammer, allowing it to fire as soon as the bolt is back in "home" position, starting the whole process over again. the trigger remains down and the bolt carrier "fires the gun" from this point on until the trigger is reset again, stopping the process.

The bolt carrier for the M16 has more metal in a certain spot than the semi's as well, this extra metal is what trips that auto sear to let it know the bolt carrier is "home" again and ready to fire.

Now, some will say there is a way to do it by just getting that semi sear to "disappear" but that really doesn't make the gun full auto, it makes the hammer follow the bolt forward basically creating an intentional slam fire. This is very dangerous in that on many guns the cartridge can fire before the bolt is locked in place, firing "out of battery". Many times when that happens the shooter loses body parts and the gun shreds itself. That assumes the intentional slam fire even works. Most of the time nothing happens, the hammer follows the bolt too closely and doesn't hit the firing pin hard enough to do anything at all. So, it's a dangerous, illegal, and mostly useless "trick". The loss of body parts should be scarier than prison with the slamfire method :)

It's not an unreasonable question, and the answer doesn't really give you any info on how to actually perform the conversion so I'm not sure what all the fuss is about.

If I ask how cars can go 200MPH would there be such panic?

rcmodel
May 31, 2008, 03:25 PM
The point of "if you can do it" is moot anyway.

It has been illegal to modify or manufacture a new civilian machinegun since 1986.

So, you can't get ATF approval no matter how hard you try, or how much you pay.

rcmodel

Chipperman
May 31, 2008, 03:28 PM
If I ask how cars can go 200MPH would there be such panic?


The Brady Bunch is not trying to prevent people from building or buying cars that can go 200MPH.

TexasRifleman
May 31, 2008, 03:30 PM
The Brady Bunch is not trying to prevent people from building or buying cars that can go 200MPH.

Don't kid yourself. EU wants to ban cars capable of exceeding 101MPH.

It will hit here next.

"They" want to protect you from more than those silly guns and knives. You need to be protected from EVERYTHING.


http://www.autocar.co.uk/News/NewsArticle/AllCars/225964/

IndianaBoy
May 31, 2008, 03:43 PM
http://www.quarterbore.com/images/JCBDIAS_01.JPG

Chipperman
May 31, 2008, 03:46 PM
Did you get that out of Shotgun News? :uhoh:

Even a drop in auto sear by itself will not make the gun full-auto.

TexasRifleman
May 31, 2008, 03:57 PM
If we're posting photos of hacks, here's another.

I have one of these, all legal like and everything!
$275 for 2 stamped pieces of sheet metal (in 1984).
Sadly, and sickeningly, these sell for $8-10k or so now.

I've heard there were close to 1000 of these things registered but I don't know if that's true or not.

Takes more than just dropping this thing in that's for damn sure.

Almost more trouble than it's worth. Takes a pre-89 SP1 Colt to work "drop in" but even then there is a lot of timing stuff to work out.

http://www.quarterbore.com/images/nfalightninglink-01.jpg

Chipperman
May 31, 2008, 04:20 PM
OK, here's mine:
http://i5.photobucket.com/albums/y164/Chipperman/M16rightside.jpg
The little pin above the selector pin is where the auto-sear lives. A semi-auto AR will not have this hole drilled.

Dr. Tad Hussein Winslow
May 31, 2008, 04:46 PM
Technically speaking, the answer is: Holding the trigger to the rear, combined with EITHER (a) an auto sear installed (which trips the hammer immediately after the bolt is closed), OR (b) in the case of accidental full-auto, a slam-fire, which is caused by the hammer following the bolt home, which is in turn caused by a missing or "misconfigured/modified" disconnector. Is that your question?

kentucky_Dave
May 31, 2008, 06:59 PM
$275 for 2 stamped pieces of sheet metal (in 1984).
Sadly, and sickeningly, these sell for $8-10k or so now.

That's a pretty good return in investment.
9 oz of gold for a +/- 2oz piece of sheet metal from the 80's :what: ...not bad


Sell it and get a pile of devalued FRN's in exchange!:neener:

Idano
June 1, 2008, 04:42 AM
Just install the hammer springs in backwards, then when you're not expecting it the pin that goes through the trigger will walk out and presto. The trigger drops and your full auto until you run out of bullets. I found this out unexpectedly one day shooting ground squirrels, fortunately I only had seven rounds in the mag. It definitely got the adrenaline pumping and by the way I did get the ground squirrel I was shooting at; I think on the first round the others were just in the general direction.

Glockman17366
June 1, 2008, 09:45 AM
The thing that concerns me about the OP's question is, sooner or later, some idiot is going to modify a legal sporting rifle (AR or AK type rifle) in to a full auto. Then, they'll do harm...either by killing folks or some lesser evil.
How to modify rifle questions have been around as long as I've been on the internet (since '93 or '94) and is readily available at various other sources.

I sure would hate to read about a mass murder then find out the perp modified his rifle from instructions from THR or other pro-rights forum. That would not help our cause at all.
That's why I suggested to do a search on the web...info is out there if the OP puts out a little effort

TexasRifleman
June 1, 2008, 10:08 AM
some idiot is going to modify a legal sporting rifle (AR or AK type rifle) in to a full auto.

It's actually pretty hard to do and have it actually work right.

Even back before Hughes people weren't just drilling their lowers and slapping in auto sears. It take some precise machine work to get it done.

Semi lowers have extra metal that has to be manipulated in several places to get it to work in addition to the extra hole.. It takes a skilled machinist to do it right even if you have all of the parts in hand. At least on the AR, no idea on the AK.

Eric F
June 1, 2008, 11:19 AM
Answering the OPs question can prospectively land one in trouble.


Since when is asking and answering any question of questionable legality?

Neo-Luddite
June 1, 2008, 11:49 AM
These kind of discussions are not encouraged here much on THR as they often stray into 'how to break the law' and that's not allowed.

That said--this *IS* America and you certainly can discuss just about anything you please without fear provided it remains academic discussion.

However, as one gets older maybe--one appreciates that it is unwise to openly teach things in a public forum that might get someone hurt or jailed.

Not saying at all that this question had any ill-intent behind it.

If you ever REALLY wanted to make a semi gun go full-auto---just contact the ATF Technology Branch; they seem to be able to do it all the time.

AR-15 Rep
June 1, 2008, 12:45 PM
There are multiple parts that make a AR-15 into a functional full auto rifle. They are restricted and there are heavy penalties if you do not have the proper paperwork and licensing for such. They have looked at it so much that designs of lower receivers on some have been modified to not allow full auto parts to be installed.
Questions about full auto parts will not get you in trouble, having them in your possesion, without the paperwork will...
Keep in mind... you can not purchase full auto parts without paperwork filed accordingly.

TexasRifleman
June 1, 2008, 03:41 PM
Keep in mind... you can not purchase full auto parts without paperwork filed accordingly.

That's not correct.

I can buy all the auto sears, 3 round burst kits, and full auto bolt carriers that I want.

It's the possession of those items and what I do with them that can become a crime.

There are many many people shooting semi AR's with full auto bolt carriers in them. In fact, Colt ships many AR's with just such a full auto carrier installed from the factory.

You can mail order the sears, hammers, etc from various sources without any problems either. The parts themselves don't DO anything.

It's when you are in possession of these items along with a receiver that you can get into trouble with the "constructive intent" and all that stuff, but buying the parts is not by itself a crime and does not require any kind of tax stamps etc.

Same with short lowers. You can buy all the 11" AR barrels you want. That in and of itself is not a crime.

If I don't own an AR, don't know anyone that does, and I have a ziploc bag full of M16 sears there is no crime. Might get me investigated a little but it's not in and of itself illegal.

Now, having an AR lower with that "extra" hole drilled in it can be a crime in and of itself. That "constructive intent" mess again, which I don't pretend to understand completely but there are people on THR that can explain it very well.

The EASY way to avoid any problems is to not have any of the auto parts at all, but there isn't an automatic crime committed by having some.

AR-15 Rep
June 1, 2008, 04:09 PM
I guess I should have said "from Me". I like to be a responsible vendor and not encourage things that could get others in trouble. Plus when ATF wants to look at records of FFL parts that went out, I like to have the paperwork so they don't have to knock on doors and investigate the possibility of someone having an illegal firearm. If I have the paperwork and it is all legit they won't have to bother someone who is a law abiding citizen.

TexasRifleman
June 1, 2008, 04:12 PM
You keep a record of parts that you sell and let ATF look at those?

Why?

AR lower parts are not regulated items and you don't need an FFL to sell them.

Other than the lower receiver itself, no AR parts are regulated, as far as sale, in any way.

There is much confusion around this point in the gun world.

If a dealer asked me to show a copy of my Form 1 or 3 before he would sell me AR lower full auto parts I would find another vendor.

I don't guess I understand the reasoning behind your thinking, I'm not trying to be rude.

That Form 1 or 3 is a TAX FORM, not a gun license and my tax forms are no one's business but my own.

jhco
June 1, 2008, 04:19 PM
after posting i thought about it an deleted my post sorry

El Tejon
June 1, 2008, 04:21 PM
peck, Fulton Armory sells a training film (on DVD) from 1950s that explains how small arms (including fully automatic weapons) function via different systems. I purchased it for my nephews and I can highly recommend it.

U.S. Army Training Film: http://www.fulton-armory.com/

From Fulton Armory webpage: "40 min/b&w - "The Fundamentals of Small Arms Weapons" filmed in the 1950ís, is an instructional video on the basic working operation of a M1 Garand rifle. The video covers many other types of small arms including the B.A.R., M3, .45 pistol, and .50 caliber machine gun. This is a fascinating instructional video on how a gun really works. Using a giant-sized replica, an Army instructor shows the inner workings."

xjchief
June 1, 2008, 04:26 PM
It's certainly interesting to see how and why the auto versions differ from the semis so thank you to those that posted.

Interesting to see how many of us are scared to death to even discuss this issue considering we supposedly live in a free society.

AR-15 Rep
June 1, 2008, 04:31 PM
AR parts no problem and ATF is not interested in those, however M-16 parts thats another story.
My reasoning is this...If there is a way to avoid problems and confusion for customers then lets do it that way. I realize that you can purchase items seperately and technically not have legal issues for having machined parts only, but most will have a grey area situation and by the time it gets sorted out, my tax dollars, your tax dollars, and that persons legal fees would not have to be spent if things were done the right way.

TexasRifleman
June 1, 2008, 04:32 PM
AR parts no problem and ATF is not interested in those, however M-16 parts thats another story.

No, they are not a different story. Only receivers are regulated in any way, sales wise.

AR-15 Rep
June 1, 2008, 04:45 PM
I did not say they are regulated, but they are of interest

AR-15 Rep
June 1, 2008, 04:50 PM
Besides what would you do with just M-16 fire control parts? I am sure no one wants to have them just as a conversation piece.

TexasRifleman
June 1, 2008, 05:06 PM
Besides what would you do with just M-16 fire control parts?

Well personally I have a legal use for them, but that doesn't mean I am willing to send a copy of my Form 3 to someone who is just selling me machine parts.

Since there is no legal problem with selling and buying them I just can't figure out why a vendor would want to track them simply because the ATF might find them "interesting".

There are enough regulatory and record keeping issues already without self-inducing more.

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