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3 round burst

39K views 31 replies 12 participants last post by  soundguy 
#1 · (Edited)
Guys, I have a kind of hypothetical question. This is for those of you who know the mechanics of an AR 15 much better than I do and I haven't even yet finished mine.

For the record, before even attempting this, I would get a BATF tax stamp for the rifle.

So, What would I have to do to modify the rifle to have a 3 round burst mode?

I did buy a full auto BCG for it (so now I just need to get an upper in pieces or ready - depends on price and what I find).

I know that some of the lower parts would have to be changed. The very obvious parts that would have to be changed is the switch selector. When I put the lower together the selector only has 2 positions - fire and safe. So, there would have to be a 3rd position for it.

So, what would have to be done technically to modify an AR 15 for a 3 round burst mode?

Military rifles have that option. How is it done?

I state again, I would NEVER make the modification without obtaining a tax stamp for the rifle. I have no desire to break laws and end up in prison with a big, fat, axe murderer behind me.

I simply would like to know technically how this works. It's just my curiosity nature.

Will

Edit to add: I don't even remember all the names of the parts I put into the lower receiver. I remember most of them and as I put it together I learned a lot of new words that pertain to gun workings that I had never even heard of. I'd like to know the difference between the parts that are in the lower now versus the parts that can provide a 3 round burst mode. I bought a full auto BCG on the advice of my FFL friend who is a manufacturer. I know he could explain it to me, but, call me dyslexic or something, I like to read to understand, then see it. I had no idea what a 'detent' was when I started assembling my lower. I didn't know how a part would be 'staked'. Now I do know these things + more.

Thanks guys
 
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#3 ·
Hypothetically.

Do you have a full auto rifle that you wish to convert to 3-round burst? That's maybe doable. I'm sure it would take a different type of sear, and the sear would be papered, so it would have had to be made and papered prior to May of 1986. And it would cost you several thousand dollars.

That's my opinion. I could be wrong.

Or do you have a semi-auto rifle you wish to convert to a 3-round burst? There is no legal way to do that. You would be "making a machine gun" after May 0f 1986.
 
#4 ·
Just for starters there would be a certain amount of additional milling that would need to be done to the lower reciever. Full auto BCG don't mean nothing, a regular ole BCG would do the job.

It's not worth it Will, black SUV's in the middle of the night and all....
 
#5 ·
Stay as far away from the government as you can, you don't want them digging into your life for any reason.
 
#6 ·
As said, no legal way as of now unless you can find a full auto lower for sale that you can afford or find a RDIAS. Both will require a Tax Stamp (Registered) to own and both expensive.

But just to clear up something said about about machining the lower.

Some AR lowers are "high shelf" some are "low shelf". Low shelf lowers would not require machining.



This is a list of companies showing who makes high shelf and who makes low shelf AR-15 lower receivers. This is in reference to RDIAS compatibility. RDIAS is Registered Drop In Auto Sear. A RDIAS, which can be found for much less than an registered M-16 or other AR-15 compatible registered select fire lower receiver. Here is a link that goes in to depth on the RDIAS- www.quarterbore.com/nfa/dias.html

Aero Precision - high shelf

Ameetec - low shelf

Anvil Arms - low shelf

Armalite - high shelf

Bushmaster - low shelf

CMMG - low shelf

CMT - high shelf

Colt - high shelf

Double Star - low shelf

DPMS - low shelf

DTI (Del-Ton) - low shelf

Essential Arms - high shelf

Fulton Armory - low shelf

LAR - low shelf

LMT - high shelf

Mega - low shelf

Olympic Arms - high shelf ?

Rock River Arms - high shelf

Spike's Tactical - Bullet Selector Markings = high shelf / Fire/Safe Selector Markings = low shelf

Stag - high shelf

Sun Devil - low shelf

Superior Arms - high shelf
 
#7 ·
Or do you have a semi-auto rifle you wish to convert to a 3-round burst? There is no legal way to do that. You would be "making a machine gun" after May 0f 1986.
If a 'pre-ban' registered auto sear is purchased it can be done. According the the BATFE the auto-sear ITSELF is considered a "machine-gun" therefore since it is registered as the machinegun (The sear itself is individually serialized) whatever rifle it is in would be irrelevant. Same situation with the Glock conversion below as an example:

"A Glock conversion switch is a part designed and intended for use in converting a semiautomatic Glock pistol into a machinegun; therefore, it (the conversion device) is a "machinegun" as defined in 26 U.S.C. 5845(b). Glock conversion devices are considered post-May 19, 1986 machineguns and may only be lawfully possessed by properly licensed Federal Firearms Licensees who have paid the appropriate Special Occupational Tax (SOT) required of those manufacturing, importing, or dealing in National Firearms Act (NFA) firearms."
 
#9 ·
You can build a new machine gun. IF you are a SOT Type 2 FFL. And you have a law-enforcement-agency client that wishes to buy it, and has made these wishes known on official department letterhead.

I don't believe that "Joe's Machinegun Shoppe", the local Type 2 SOT, could convert 50 AR15s to M16s just because they "think they can sell them to the local police force". I believe they have to have an order first.

Remember that dumb Discovery Channel show about the gun shop in Louisiana? The local sheriff brought in his personal 1927A1 Thompson carbine and wished them to convert it to full auto. The only way they could legally do that would be for him to give (or sell) the gun to the Sheriff's Department, and then the SD request the conversion, on official Baton Rouge Sheriff Department letterhead (for the shop's records). According to the show, that's not what happened. They just converted the Sheriff's gun for him. Totally illegal.
 
#11 · (Edited)
I'm fully aware of the legal implications guys and I certainly wouldn't do it without getting a tax stamp approval first anyway. I was just curious what would be involved or even if it's possible to modify a standard AR 15 to have a 3 round burst mode. Modifying an AR to have a full auto mode isn't difficult because all you really need is a full auto sear plus changing out the fire selector to have a full auto position as long as you have a full auto bolt carrier group. I don't want to make it full auto anyway even though I did buy a full auto BCG. I just want to understand the how the parts would work for a 3 round burst mode. I seriously doubt that it would be worth the investment to change it and get a tax stamp for it + I do agree with the advice of keeping out of the governments radar. I posted the question only because I am curious as to how the actual parts work for a 3 round burst mode. I know the military rifles have a 3 round burst selector, but, how does it work? What parts make it work in such a mode?

My local FFL who's website I maintain does have full auto AR's. He's also a type 7 FFL and is a manufacturer. that's his business. He has everything perfectly legal of course also. Tax stamps for all the full auto firearms. When I took my lower to him to check how I did putting it together and have him tighten down the castle nut for the butt stock we were having a conversation and he advised me to make sure I bought a full auto BCG. His reasoning for telling me to do so was that ever SHTF happened, the rifle 'could' then be modified to full auto if necessary. I'm sure he can explain how the three round burst mode actually works because he's also a gunsmith. I don't know when I'll be down to see him next is all. So, I asked you guys.
 
#12 ·
GunHugger do you know where the Mag Tactical Systems lower receivers come in at?
 
#13 ·
Interesting thread, I've learnt something new today. :D
 
#14 ·
GunHugger do you know where the Mag Tactical Systems lower receivers come in at?
No, I tried to find the answer but failed to do so.

If you own one, compare it to the picture I post above.
 
#15 ·
I do own one GunHugger and I'll check and post back. I'm still curious though as to how a three round burst mode actually works. I understand the difference between full auto and semi auto easily enough, but how does the 3 round burst mode work? What stops the full auto function after only 3 rounds?

There are certainly guns I'd be willing to pay the tax stamp for to have in my collection and the Thompson .45 is at the top of that list if I ever find one I can afford.

I'm thinking that it must be some kind of trigger interrupt for 3 round burst fire because an auto sear will keep cycling as long as the trigger is depressed until there is no more ammunition.
 
#20 ·
I do own one GunHugger and I'll check and post back. I'm still curious though as to how a three round burst mode actually works. I understand the difference between full auto and semi auto easily enough, but how does the 3 round burst mode work? What stops the full auto function after only 3 rounds?

There are certainly guns I'd be willing to pay the tax stamp for to have in my collection and the Thompson .45 is at the top of that list if I ever find one I can afford.

I'm thinking that it must be some kind of trigger interrupt for 3 round burst fire because an auto sear will keep cycling as long as the trigger is depressed until there is no more ammunition.
google 3 rd burst. everything is on the interweb.

i think you are not understanding the way it goes. the tax stamp is $200. a Thompson 45 auto will cost you close to $20 grand. you first pay the 20k, send the paperwork and in a year, if you pass an FBI background check you get to go get your weapon.
it is actually not legal for you to have an M-16 lower parts kit in your posession if you own an AR-15.

having a full auto bolt carrier makes no difference anymore. at one time they made mostly AR 15 carriers now there are more M-16 carriers made. M-16 carrier is just heavier unless you have a registered reciever or a drop in auto sear or a lightining link. all 3 things cost thousands of $.

if you own a registered reciever there is a full auto parts set and a 3 rd burst parts set AND there is a little known set that gives you both, 4 position selector.

lots to learn at the sight where i found my machine gun. Sturmgewehr.com then go to NFA market board.
 
#16 ·
#17 ·
It's not a matter of getting a $200 stamp. A private citizen cannot manufacture a machine gun. Period. No way, no how. A dealer with SOT classification can make one as a sample but that cannot be transferred to anyone except another SOT if and when the dealer decides to terminate his license.
 
#18 ·
Thanks a lot GunHugger. That is exactly what I wanted to know. Now I understand how 3 round burst mode actually works. So, I have learned something :)

Medalguy, I have no intention of building a machine gun. It would waste way too much ammo for a starter. I just wanted to know how the 3 round burst mode works. By examining the description, it would be quite difficult I think to even add that feature to a standard AR15. I suspect that the lower receiver would have to be modified to accept the cam that controls the 3 round burst. I am happy now to understand how it works though and my lack of knowledge now has been cured. :)
 
#19 ·
It's not a matter of getting a $200 stamp. A private citizen cannot manufacture a machine gun. Period. No way, no how. A dealer with SOT classification can make one as a sample but that cannot be transferred to anyone except another SOT if and when the dealer decides to terminate his license.
i believe the SOT can keep his samples at the conclusion of his SOT status. but if they are ever xfered.. they must go to another SOT.. no form 4 to average joe.. etc..
 
#21 ·
Soundguy, there are two types of "dealer samples".

First, there are three types of papered guns. Ignoring "Police guns".

TRANSFERABLE. Them's the ones that me and thee can own.

PRE-86 DEALER SAMPLES

POST-86 DEALER SAMPLES

Dealer Samples can only be sold to a dealer. If the dealer had a Dealer Sample that was registered prior to May of 1986, while he can only SELL IT to another dealer, if he decides to give up his license, he can keep that one. It will be repapered as a transferable gun, and Joe Citizen (as opposed to Joe's Machine Gun Shoppe) will own the gun.

If he has a dealer sample that was papered AFTER May of 1986, he can't keep it. Period. If he decides to give up his license, he can either sell it to another dealer, or give it to the ATF to be destroyed.
 
#29 ·
Hmm.. The ATF told me opposite of that...

I was looking at a 712 schnel one time. current dealer listed it as being xferable, when it came time to sell, he backed out as he found it was papered as a sample. it was a pre 86 sample too. the atf told us he could keep it when he let his license go, but it stayed a smaple and did not get re-papered. I actually considered getting my class III just to get that gun... but it never happened.

Mind you this was over a decade ago.. so maybee atf rulings have changed. can anyone cite a ref that shows a pre 86 dealer sample gets dropped to a form 4 type weapon for regular tax paid transfer?
 
#23 ·
I've got a "burst" question.

Will a "burst" trigger fire three rounds every time? With my MP5, I can hold it down and shoot 30 rounds, or get on and get off and shoot lesser amounts. Doing a 4-round burst is simple, a 3-round is easy, a 2-round is doable (never managed just ONE on full, but I've tried, often).

But with a "burst", will it, no matter how fast I get on and get off, shoot three? Once that trigger is pulled, it's gonna shoot three times, even if the shooter dropped the gun?
 
#28 ·
I've got a "burst" question.

Will a "burst" trigger fire three rounds every time? With my MP5, I can hold it down and shoot 30 rounds, or get on and get off and shoot lesser amounts. Doing a 4-round burst is simple, a 3-round is easy, a 2-round is doable (never managed just ONE on full, but I've tried, often).

But with a "burst", will it, no matter how fast I get on and get off, shoot three? Once that trigger is pulled, it's gonna shoot three times, even if the shooter dropped the gun?
Nearly every 3 round burst will only do whatever you pull the trigger back for. Example: If you are really quick with your finger, it will only do 1 or 2 rounds. A single trigger stroke can only produce a maximum of 3 shots before the interrupter engages the sear to stop the firing. Now, some interrupters continue on the same three count(if you only shoot 1 or 2 rounds, it will only shoot 2 or 1 round respectively until it resets on the 3rd shot and after you let up on trigger). Some reset upon letting up on the trigger, so the next trigger pull will have a max of 3 rounds.
 
#24 ·
the wife and i, i claim them, have 2 sons in the Army. one is a West Point Grad Captain that went to Iraq, and another is a Staff Sargent that was in Iraq and Afganistan. Sargent told me how 3 rd works but i dont remember exactly. i do remember he said as the burst part works it could be interupted, firing 1 or 2 rds but the next trigger pull will give you 3. so its not exact unless maybe letting off quick does interrupt the cycle.
im speaking of M-16 though.
 
#25 ·
Ever since I helped to develop this ( ) Phalanx 20mm machine in the 70s, I've wanted to duplicate it in .22 LR for rabbit hunting from a quad. Based on this discussion, I'm guessing somebody might have a problem with that.:rolleyes:
 
#27 ·
I can't afford depleted uranium, so we're good to go.

Phalanx CIWS (Close-In Weapons System) is based on software that can track two targets at once using radar - the incoming weapon (originally assumed to be a cruise missile, but since redefined), and the stream of uranium bullets being emitted by the GE 6-barreled gun. The software's job was to make the two dots on the screen occupy the same space by moving the gun barrel.

My plan was to use IR technology to track two targets, as well; one a warm bunny, the other a stream of hot lead projectiles. The accuracy would be excellent, as even in the IR range, the wavelength is much shorter than microwaves used for radar. But at (classified) rounds per minute, it will be hard to feed the thing when .22 LR isn't available. Maybe I should redesign my system to use .223, since that seems to be plentiful these days...
 
#30 ·
That may be. I was never a dealer. I thought that, after giving up the license, you could keep your pre-86 samples and they became transferable. But it's quite possible that they just are allowed for YOU to keep. You can't sell 'em, or give 'em away, or will 'em. And after you shuffle off this mortal coil, ATF gets 'em.

But I DO KNOW, that if you have pre-86 samples, and you give up you license, you can keep the pre-86 samples.
 
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