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Old May 24, 2007, 04:13 PM   #1
hybrid
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Burst fire in the M16

Let me start off by saying that Im pretty impressed with this particular forum so far. Ive lurked a bit and only dare ask this question cause I dont see the usual crap that goes on in other forums that are firearms related..........I wont mention the others.

In anycase Id like to have some myths and mysteries cleared up for me.

What exactly seperates a civilian "AR15" from the "M16"???

I hear all kinds of lightening links and drop in auto sears and crap like that for conversions but alot of people also say that they are unreliable at best and are more likely to get your face blown up with a scattering shrapnel gun reciever.

This leads me to the title of the thread.

How does the burst fire work? How can they set up a gun to bump off 2-3 rounds only and not just stick into full auto and therebye wasting tons of ammo?

Is it true that most of the M16's issued now dont even have a full auto position due to the idea I just elaborated on "spray and pray"????

I have tons of other questions but I want to see what this stuff gets me. Im an enthusiast who is just generally curious.
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Old May 24, 2007, 04:27 PM   #2
Jason_G
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Quote:
Is it true that most of the M16's issued now dont even have a full auto position due to the idea I just elaborated on "spray and pray"????
The M-16A2 has only the single shot and 3 round burst trigger group (to my knowledge, I may be wrong though). There are other variants that have full auto capability (M4 carbine, I believe, and maybe CAR-15). I'm not really an expert on this, but nobody had chimed in yet, so I thought I'd offer what I could.

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Old May 24, 2007, 06:17 PM   #3
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What I don't get is why the Carbine has the Full Auto but the full size M16 only has the Burst fire.
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Old May 24, 2007, 06:33 PM   #4
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Quote:
why the Carbine has the Full Auto but the full size M16 only has the Burst fire.
Its just a preferance. You can drop in any of the different fire control sets into any M16 receiver. They make fire control sets that are:

safe-semi-burst-auto

safe-semi-burst

safe-semi-auto
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Old May 24, 2007, 10:10 PM   #5
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It's the extra parts that makes an AR have burst capability. Actually, burst fire is for armies that fail to train its troops in trigger control. An experienced user can easily attain a two or three shot burst when the selector is set to full auto. This comes with practice - something the armies tend not to invest time in.
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Old May 25, 2007, 12:24 AM   #6
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There are many variants to the M16 rifle.

M16 - first model.
M16A1 - added birdcage flash suppressor and forward assist.
M16A2 - Longer stock, heavier barrel. Burst capable.
M16A3 - The A2 with full auto.
M16A4 - Detachable carry handle, full size rifle, can be had with full auto or burst.

The M4 Carbine usually comes in full auto flavor; it can, however be ordered in the burst mode.

The burst function is controlled by a double disconnector on the trigger, and a burst cam on the right side of the hammer assembly.

The burst equipped rifles CAN be easily changed to full auto--but I won't discuss how to do it here.
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Old May 25, 2007, 07:32 AM   #7
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The burst cam that Powderman speaks of is basically a little wheel with 6 teeth on it, and 2 of those teeth (180 degrees apart) act as "stop points" for the burst. In operation, when you pull the trigger and it's set for burst, the wheel advances one tooth every time the bolt carrier cycles, until you hit one of those stop points, then you have to release the trigger and squeeze it again to get another burst. One of the downsides to this system is that if you only fire one or two rounds out of a "three round burst", and then squeeze the trigger again (expecting a full three rounds), you'll only get the remaining one or two rounds from the previous "burst".
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Old May 25, 2007, 09:29 AM   #8
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I'm sure there are still M4s lurking around in full auto, or there were a few of them about a year and a half ago. All of the ones in my company were burst in Iraq. Only time there is a need to go into burst or full auto, IMO, is when the SAW and 240 are down and you need to suppress until they get back up. Some use burst when clearing buildings, I have done it, but I don't really see the advantage.

+1 burst is a mechanical fix to a training error.

The civilian AR from the M16??? The burst selecter, Fabrique Nationale made (very few civilians have the FN), The bolt carrier on the M16 has the metal on the bolt carrier that resets the sear as the bolt returns to battery allowing full auto or burst... I think thats most of it.

LET ME STRESS THAT THERE IS NO WAY TO LEGALLY TURN AN AR15 INTO BURST OR FULL AUTO. Drop in sears are not illegal to make. They are illegal to own if you own an AR. I've not heard much good about the bumb fire mechanisms. The only way to own true full auto is to buy a registered transferrable pre 86' class III along with the tax stamp for it. I couldn't see where a drop in sear would cause the gun to blow up, not unless you have about 4 beta mags and you run them all through at the cyclic rate. Even then it will just melt and not blow up.
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Old May 25, 2007, 10:41 AM   #9
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Quote:
Drop in sears are not illegal to make.
Absolutely wrong. It is a felony to make a drop in sear if you are not an 07/SOT.
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Old May 25, 2007, 12:09 PM   #10
hybrid
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SDC.............THANKS!

You have given me a start.

I have absolutely no idea of what youre talking about..........(im not a gun smith yet and can only field strip my weapons for cleaning so far) but I like knowing that there is in fact a machanism for controling the sear versus the bolt.

Anyone have an actual picture or diagram of how it works?

Oh and I cant see why anyone wants a full auto in the first place........what good is 30 rounds of ammunition flying when 99% of it isnt aimed at anything.

I think most smart shooters know that full auto is for keeping heads down until you can cover and take single shots at your foes.

And on the discussion of all the ILLEGAL conversions...........how do those work at all if everyone says that they are actually not any good? I hear nightmares about how guns fire out of cycle or something (sorry still a newb with the technical jargon) and go boom.
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Old May 25, 2007, 12:42 PM   #11
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Hi, Hybrid, I have almost telepathic feelings regarding your post concerning 3 shot bursts, FA fire and so on. I simpathize as I once had the same curiosity but realized that "It just flat out isn't worth it" !!!!

Violations of the Gun control Acts of 1934, 1968, and other determinations by the ATF has penalties that certainly discourage firing more than one bullet per trigger pull. Merely owning an autosear and an AR type rifle is a no-no,
Auto sears require some M16 parts in the upper and lower receivers which is also against the law. One may with the proper paper work, police checks, a $200 tax stamp be allowed to posess a machinegun but their scarcity makes
them prohibited because of the cost perhaps in the thousands of $$$s......

What we have to worry about now is HB1022 which would ban even semi automatic firearms and a host of others, this being pushed by the liberal Democrats generally. You can't vote with a machinegun but a paper ballot from enough of us can send the anti gun crazies back home and out of the
House and Senate!!!! Join the NRA today, help in our battle.

Last edited by cuate; May 25, 2007 at 12:45 PM. Reason: one word wrong
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Old May 25, 2007, 01:14 PM   #12
hybrid
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Dude...........what?

AGAIN...............I have never mentioned any intent as to my wanting any parts to conversions.

Im merely a mechanical geek and have a hobby with guns. Ive been buying lame arsed books on gun smithing so that perhaps I could start to understand the mechanics behind modern firearms...........flint locks are kindof easy to get you know?

What makes you think Im not already a member of the NRA and that I dont donate money to the cause personaly and with every purchase I make at MIDWAY?????

BTW...........1022........Ive already done what I can. Donated money to NRA and GOA and written all my state reps.

So can we now get on with some technical information instead of the donnas coming into lecture me about the evils of ILLEGAL conversions?

Just to be clear, Ill reitterate it ONE MORE TIME

I DO NOT WANT NOR INTEND TO BUILD ANYTHING ILLEGAL...............I JUST WANT TO UNDERSTAND HOW AN AUTOMATIC WEAPON ACTUALY WORKS AND HOW SPECIFICALY BURST WORKS.

Knowledge and information is NOT a crime.
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Old May 25, 2007, 01:24 PM   #13
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My apology offered !!!! Good luck in your gunsmithing quest, good luck in all of your endeavors, I stand corrected. Sorry that I misunderstood your questions......
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Old May 25, 2007, 01:33 PM   #14
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Well, you have to see it from our viewpoint--this is your third post, and you are asking for detailed information on equipment and mechanisms which (unfortunately) are restricted.

Here's a starting point...

Do some research, and find out all you can about the following Colt rifles:

M16/M16A1--select fire capability, with basic full auto equipment: uncut bolt carrier, auto sear w. compatible hammer, selector.

M16A2--Select fire capability, burst fire equipment: uncut bolt carrier, auto sear w/ compatible hammer, double disconnector, selector, burst cam.

M16A3 is the A2 w/ full auto. Spec'd by the Navy.

M16A4 has the detachable carry handle.

For specific model numbers, you can look up the M4/M4A1--one has burst, one doesn't, under Colt model number R0977.
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Old May 25, 2007, 06:15 PM   #15
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the M4 Carbines are Burst, the M4A1 Carbines are Full Auto...

evidence this photo of an M4A1:



david
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Old May 26, 2007, 01:05 PM   #16
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As far as the BATFE is concerned, if it has the auto sear pin hole (the third pin hole above the selector), it's a machine gun.

If you want to understand how an M16 works, watch this video.
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Old May 27, 2007, 08:02 AM   #17
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Full auto has it's place in combat. Suggest you read up on battlefield tactics, ambush techniques, and suppression fire. You don't always need accurate fire, so that you can survive to fight another day.
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Old May 27, 2007, 10:18 AM   #18
4V50 Gary
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Quote:
Full auto has it's place in combat. Suggest you read up on battlefield tactics, ambush techniques, and suppression fire. You don't always need accurate fire, so that you can survive to fight another day.
Absolutely! The trouble is that the Army doesn't really train its soldiers in trigger control and concern for ammunition supply (logistics) resulted in the burst feature in lieu of full auto. The Marine Corps got it right by keeping the older safe-fire-auto mode on their version of the M16.
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Old May 27, 2007, 10:05 PM   #19
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The main disadvantage to the M16 burst mechanism in my opinion is the way it causes the trigger pull in semi-auto to vary from shot to shot. I can see how the lack of a burst "reset" feature would be frowned upon, too.

Regarding full-auto in combat, here's the opinion of one combat vet:

Quote:
I got to make a few comments regarding what's good and not in combat arms. It is only my experience but 2.5 years on combat put a rather sharp point on my perspective.
...
Rate of fire is an issue that interests a lot of folks. Well hell it looks/sounds neat. Nothing quite so nifty as the sound of a mini-gun. There is only one time in combat that FULL AUTO is useful and that is during an ambush. Defensively, the noise is distracting to the attacker; Offensively, the range is usually close, and higher rates of fire assist with saturating the kill zone with lead. 650-800 rpm is just ducky. Less leaves gaps, more eats up your ammo too quickly. It is simply the nature of things.
Link: http://www.handloads.com/forum/showt...c=5&thread=306

At least one US military manual says that rapid semi-auto fire is better than full auto in every way at distances greater than 25m:

http://www.thefiringline.com/forums/...3&postcount=57

But yeah, for close-range ambushes where a rifle squad is using its combined firepower, it can be seen how controllable full-auto would be an asset. For everything else, I can't imagine why 5-6 rounds per second (easily achievable on semi-auto with a decent trigger) wouldn't be enough. Maybe I'm wrong, and I've never been in combat, but this is just MHO.

Speaking of 5-6 rounds per second, I've heard that some new Russian AKs have rate-limiters installed to reduce the cyclic rate to ~300 RPM. Has anyone else heard about that?
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Old May 28, 2007, 08:42 AM   #20
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To answer your question hybrid -

generally speaking, factory built or SOT converted full-auto capable weapons have some means of retarding the hammer from falling until after the bolt is locked.

generally speaking, illegal bubba jobs don't.*

And so generally speaking, aside from risking jail time bubba has a gun which doesn't mechanically guarantee the bolt is locked before the hammer falls. On either count, he might get lucky. Or he might not.

As to how the burst mechanism in an A2 does what it does, I know there's a little "how things work" page on it out about on the web somewhere. Little turning cam dohickey, as Powderman and SDC say.

-K

* Although lightning links and drop in auto sears are both ways of jury-rigging said delay. The latter requires other M16 parts in the gun to work, but provided it's properly fit should be safe. The former... I've never seen in action, but just looking at how it does what it does I wouldn't put in a rifle I had even if it was legal.

Last edited by Kaylee; May 28, 2007 at 09:32 AM.
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Old May 28, 2007, 10:35 AM   #21
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I've never seen in action, but just looking at how it does what it does I wouldn't put in a rifle I had even if it was legal
And there are legal Registered Lightning Links (RLL's) and Registered Drop In Auto Sears (RDIAS's) out there that were registered and numbered prior to May '86. They can be made to work properly and safely, just ask Shaggy.
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Old May 29, 2007, 04:58 PM   #22
hybrid
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Some great additional answers guys! Thanks.........Im gonna look at some links and see if I cant figure out the mechanics of it all.

Like I mentioned, full auto I get..........Semi auto I get. True burst seemed a bit confusing to me especially when it contains extra parts in the same frame.
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Old May 31, 2007, 01:27 AM   #23
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I pulled this out of a Bushmaster catalog. Maybe it will help...

Last edited by kkb; May 6, 2008 at 11:12 AM.
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Old June 5, 2007, 02:29 AM   #24
Herbert
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m-16 Burst

Burst is just automatic with the trigger having a built in mechanism called the burst cam to lock the hammer down every third round.

After a round is fired in the m-16 the bolt is pushed backwards using gas from the gas tube. As the bolt is pushed back it pushes the hammer down and slides over the sear into the buffer spring. The hammer being pushed into the down position clicks the burst cam one click while the sear latches the hammer and keeps the hammer in place. As the buffer spring pushes the bolt forward into the locked position it contacts the sear pushing the top of the sear forward allowing the bottom of the sear to release the hammer which strikes the firing pin. This triggers the sequence again until three cycles are complete. Then the burst cam locks the hammer in the down position until the trigger is released and pulled again.
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Last edited by Herbert; June 5, 2007 at 02:32 AM. Reason: Correction and Grammar
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Old August 1, 2007, 01:15 AM   #25
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Burst fire was developed as a way to improve hit probability. Basically, by firing three rounds, you'd have a better chance to cover the target.

For CQ work, I personally think the way to engage with an AR is aimed rapid fire, pulling the trigger in a controlled fashion, spotting the strike of the rounds and walking them onto the target. Point shooting with a rifle, sort of.

With the new optics, it's probably quicker, more deliberate and better aimed, with fewer shots fired.

Do any of the young guys have experience with using burst fire like this? What's the state-of-the-art?

I think full-auto is for yay-hoos, except when very close...unless you have a Ppsh....or are very disciplined doing fire and maneuver with a team.
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