Do you need to have the same modifications done to a lower reciever to obtain 3 round burst as full-auto? Does it have the same legal implications? I find a lot of info on DIAS’s but I’m not looking to go full auto and I can’t find much info on 3 round burst.
well moosepn, m4carbine.com has been such a big help to me, as a member let us see if i can help you. yes if it is auto compatible(i.e. w/hole for automatic sear pin), no block over safety and mil,standard fire control pins. yes, same legal definition as machine gun, the three round bust consist only of a few more parts. if you can get your hands on USMC TM 05538C-23&P/2 it will give you all the info to see and understand the parts and there relationship to burst fire. it seems that you would need an M16 Carrier,automatic sear and its pin,compatible M16 hammer,burst cam,cam clutch, M16 safety lever and auto M16 disconnecter’s. please don’t think that i am an expert, as i am only looking at the USMC TM.i am confidant that other members more knowledgeable than me will also step in to help answer you questions. i will also continue to follow this thread in the event that my info is not correct. good luck. Don…
I like the 3 rd burst.that is what i used at ft knox .after the first 3 rds you are shooting sky or over their head.its better to control your shots.with a burst even on the 240 bravo and saw 249 short 7 -9 sec burst. full auto is fun but if you are not using it right you are just dumping ammo.I would rather control my shots make them count.plus if you need to,a quick 10 pulls of the trigger dumps the mag.I like the tri-burst
Now if you own a NFA M-16 with full auto you can put a tri-burst in fine.with no extra paper work.But using a tri-burst is a Machine gun so all the wonderful BATF and NFA laws apply:(
A weapon capable of firing more than once with a single press of the trigger is a machine gun… As a private citizen you need to follow the procedures of the BATFE and your local government outlined for the purchase of any NFA weapon… If you are in a machine gun friendly state, this can be a relatively straightforward procedure, if not you are SOL…
Buck
The legal inplications is if you dont have a 15k priced preban 86 lower it is going to send you to the Federal Pen.
Short answer your question YES- “you need to have the same modifications done to a lower receiver to obtain 3 round burst as full-auto”
You need a sear. … whether that sear is a standard military sear (which would require the receiver being registered as a machinegun) or a LL (Lightning Link) sear or a DIAS (Drop in Auto Sear). Both the LL and DIAS are considered the registered NFA machine gun.
Given that the gun has a sear the only difference between a full auto gun and a 3 burst gun is the chosen trigger group.
That sucks, but it makes sense in a communist kind of way. I’m not sure how to word this exactly but if you put a trigger group used for 3 round burst(hammer, disconnector, etc.) into a non modified lower, would it still fire single shot and just not be able to switch over into 3 round burst? Would that even be possible with out having a hole drilled into the lower?
If you understand the M16/ AR system one will understand that the “sear” does not actually make the weapon fire full-auto or burst, it only regulates it. There is another item that is needed in addition to the hammer, trigger, and disconnector.
Without the sear…the hammer disconnects too early and rides the bottom of the BCG.
It was my understanding that the “Burst” option was introduced so that the
weapon would now control the amount going down range.
Finger taps are no longer needed.
We are too stupid to learn proper techniques…RIGHT!!!
But the rifle will still fire fully automatic. It may or may not stop with the hammer down. I’ve seen this first hand on days where guys I know fire some full auto throughout the day only to realize that they didn’t even have their RDIAS in the lower.
As stated above… the sear regulates the hammer drops.
I SNAFU’ed my post. I guess what I should have said is that if you had all the items from a full or 3rd burst gun (including the overlooked piece) and the correct BCG you could make the weapon fire more than 1 round at a time. IIRC, that is why some people were cautioning others to be careful of what parts they had installed in their guns because accident or not the BATFE may not be so forgiving or understanding.
I wouldn’t say I “understand” completely how 3 round burst works. I understand that there is a difference in the design of the lower reciever as far as where the hammer, trigger and disconnecter fit into. In addition I think the bolt carrier is shaped differently and there is an additional spring and control that fit over the hammer assembly as m700m said.
So if I understand twodollarbill correctly, if I installed the lower parts of an M16 without drilling the hole for the sear and its pin, or using a DIAS the hammer would disconnect too early and effectively do nothing? Or would it fire a single shot disconnect too early than reset. I realize that might not even make sense. I’m trying to figure this out
Without an auto-sear or DIAS the hammer will not be retained properly as the BCG moves forward. It may fire, it may not. It may fire the entire contents of the magazine or it may fail to fire on the second shot. The hammer will be chasing the bolt carrier and may or may not exert enough pressure on the firing pin to sufficiently dent the primer.
It doesn’t have to be a reliable machine gun to get you thrown in jail though, it just has to do it twice- once to get you reported, and once again in the ATF lab.
Basically the one component that is overlooked is ensuring that you also have a full-auto (select-fire) selector lever. I don’t recommend that you install these parts, but if you did you may be surprised as to what happens.
There is a notched cam on the hammer pin that counts (or follows) the hammer strikes. There is a
second disconnect that extends and rides the cam and trips at the 4th count. The counting sequence
soes not reset to zero when you stop or empty a mag. You may start with a one or two round burst, then three, three, three…
Hope the Pics help
i was under the impression that removing the disconnector from a semi AR15 lower would result in a single shot followed by the hammer jamming the bolt shut on the next round resulting in a costly lecture from your gunsmith.
so you’re saying that you can fire full auto without a registered auto sear? 
disclaimer-for educational purposes only… i have ZERO intentions of creating a machine gun or any other illegal weapon.
I also have no intention of illegally making a machine gun. It may be possible.
Most any semi-automatic firearm can be altered to fire in something approximating a fully-automatic mode, but the issue is whether or not that is operator-controlled (i.e. whether or not the rate of fire is being directly influenced and regulated by the trigger or fire control system).
The ad hoc solutions being discussed here will not create a select-fire weapon, but may well result in a “runaway” weapon wherein a single trigger manipulation will send the gun into an uncontrolled firing cycle that will continue until (a) the weapon depletes the contents of the feeding device, or (b) the weapon malfunctions. That may look/feel like full auto fire for a few seconds, but in functional terms it is really nothing of the sort.
Aside from the obvious danger and recklessness associated with deliberately inducing a malfunction of this sort, NFA restrictions also come back into play here, as a single trigger activation is resulting in an automatic (if uncontrolled) mode of fire. In other words, bad idea.
Chief
Full Auto and Burst are not worth the price of admission to the club, the registered guns are outrageously expensive to buy, require governments hoops to be jumped through and waste ammo at an accelerated rate.
I fire FA and burst on Uncle Scrooges dime, for me well placed semi fire is better.
To the OP:
and old M16A1 that is FA, may with the fire control parts for the 3 rd burst be converted to fire burst, similarly the M16A2 with standard A1 fire control parts will fire full auto. If the lower is drilled for the auto sear it will be capable of being configured either way.
The RDIAS still required the FA fire control group and selector to work.
I am a little confused. Both the M16A2 and M16A1 have sears and they are identical. The difference between them firing burst or auto has to to do with the Fire Control System. As a matter of fact I have seen a few “units” that replaced their 3 rd. burst w/ auto FCS.