PDA

View Full Version : How does the AR/M16 FTG work?


Steve O
10-03-2008, 11:59 PM
Hey folks! Been having a good time her on the board, and chatting with some really nice informative people.
Basically I'm moving to a free state this upcoming year, and soon hope to own my very own M16 MG!

I meet all the requirements of the BATF, and I figure at the increasing rate of value of MG's and the increasing cost of gasoline, I'll sell the GTO if I have to! lol.
I figure this should make the desolate state of NV a bit more fun Intel I can make some new friends!

So I have been researching all I can the past few days on MG's and NFA weapons, and all the legal requirements to have title 2 weapons.
However I still lack the basics. I don't even really know how a MG works! lol.

I've seen pics on the web. But have never used a MG or seen any internal parts. I do have a OLL legally configured here in CA, so I know the internals of that legally configured, semi-automatic rifle, but have not seen anything else with my own eyes.

Does anyone have a link to a GIF file or some sort of animated pic file of how the M16 works in semi, and auto mode?
It looks a bit complicated just looking at parts kits online, but I think with the help of a animated gif or something similar, I should have a better understanding...

CHS
10-04-2008, 12:48 AM
In absolutely simplest terms:

When in FA mode, the auto-sear intercepts the hammer before the disconnector does (bypasses the disconnector, if you will), holds the hammer and sort of acts like the disconnector until the bolt/carrier come back into battery. The bottom rear part of the carrier that sticks down then smacks into the auto-sear, which releases the hammer. The bolt/carrier are fully back into battery just before the hammer hits the firing pin, which makes the gun go "boom" again. The cycle continues until you release the trigger.

The cycle continues until you release the trigger because the trigger sear holds the hammer in place before the disconnector or the auto-sear can grab a hold of it, so when the bolt/carrier come back into battery there is nothing for them to trip and set off another round.

SP1200
10-04-2008, 12:57 AM
wow! someone should make an animated gif from a diagram. And that gif can pause and a bubble can pop up for every action. lol. ok, I'm going to see if I can find a diagram and see if I can make sense of it all. Thanks!

sb_pete
10-04-2008, 2:23 AM
well here's some diagrams:
http://www.scribd.com/doc/344690/M16-Rifle-Marksmanship
starting on section 4-3 is where you want to be looking

NeoWeird
10-04-2008, 3:09 AM
In absolutely simplest terms:

When in FA mode, the auto-sear intercepts the hammer before the disconnector does (bypasses the disconnector, if you will), holds the hammer and sort of acts like the disconnector until the bolt/carrier come back into battery. The bottom rear part of the carrier that sticks down then smacks into the auto-sear, which releases the hammer. The bolt/carrier are fully back into battery just before the hammer hits the firing pin, which makes the gun go "boom" again. The cycle continues until you release the trigger.

The cycle continues until you release the trigger because the trigger sear holds the hammer in place before the disconnector or the auto-sear can grab a hold of it, so when the bolt/carrier come back into battery there is nothing for them to trip and set off another round.


ALMOST!

The safety switch on an AR-15 has no flat which blocks the trigger and subsequently the disconnector from moving and it also has a full flat which allows enough clearance for the trigger to move. The M16 selector has three or more flats which include the same flats as an AR-15 but also an additional flat(s) that allow the trigger to move but restrict the disconnector. This is why M16 disconnectors have that longer tail - it catches the M16 selector.

In normal operation, the trigger's front acts as the sear. When the hammer is cocked there is a mating notch in the hammer that mates to the trigger's sear surface and they lock together. When the trigger is pulled this sear surface is rotated out of engagment with the hammer and spring tension causes it to fly home hitting the firing pin and causing ignition of the cartridge. Gas is syphoned off from the barrel which pushes the bolt backwards pushing the hammer down as it travels rearward. Now this happens very quickly so the trigger is still depressed at this time, so the hammer attempts to rotate back towards the carrier as it closes, but the disconnector catches the hammer. As the trigger is released the disconnector loses it's hooking on the hammer which resets back onto the trigger and it has completed the full operation in semi-auto mode. (look at your lower and manipulate the FCG with your hand slowly to see this happen and it will make sense).

Now what happens in full auto is that the seletor gets rotated and it allows the trigger to move but NOT the disconnector. So the same opperation above happens except at the point where the disconnector would normally catch it, the selector is depressing the tail of the disconnector so it's rotated out of the way. The result is the hammer continues rotating until it hits the auto-sear, which is normally out of the way because the carrier is pushing it to the rear, but since the action is currently cycling it is open. So the auto-sear now catches the hammer and restricts it's movement. Then as the carrier returns home, it hits the auto-sear's tail which rotates it out of the way, which removes the last obstruction from the hammer which then continues rotating and fires the weapon again. This continues until the trigger is released and the sear surface catches the mating notch in the hammer.

Steve O
10-07-2008, 8:23 PM
I'm confused about the sear/disconnecter. When looking at a diagram of the FCG on an M16 I do see a disconnecter that sits on the trigger, then a sear that actuates hooking the upper hammer notch.

But when someone describes the AR-15 semi-auto FCG they mention a sear and disconnecter, and I only see the disconnecter in the diagram.

Quarterbore has a decent description of the actions. but again the mention of the sear/ disconnecter confuses me.

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

IN the M16 its clear that the disconnecter and sear are a separate parts.
But on the AR-15 are the sear and disconnecter two different sections of the same part?

ar15barrels
10-07-2008, 9:52 PM
I'm confused about the sear/disconnecter. When looking at a diagram of the FCG on an M16 I do see a disconnecter that sits on the trigger, then a sear that actuates hooking the upper hammer notch.

But when someone describes the AR-15 semi-auto FCG they mention a sear and disconnecter, and I only see the disconnecter in the diagram.

Quarterbore has a decent description of the actions. but again the mention of the sear/ disconnecter confuses me.

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

IN the M16 its clear that the disconnecter and sear are a separate parts.
But on the AR-15 are the sear and disconnecter two different sections of the same part?


An M16 in semi-auto functions exactly like an ar-15.
All the disconnect, hammer and trigger functions are identical.
When you rotate the selector to auto, there is an extra notch in the selector that pulls the disconnector down/back so it never catches the hammer anymore.
THEN the auto-sear back behind the hammer handles the releasing of the hammer when the carrier comes far enough forward to trip the auto-sear.

Steve O
10-08-2008, 12:33 AM
So I was thinking that the disconnecter had a part below the disconnecter hook that extended forward and downward to lock the hammer at the sear notch but turns out that it looks like the trigger actually has a extension that goes forward and that engages the sear notch on the hammer. and that releases the hammer when you pull the trigger. does this sound right?

So what is the actual "primary sear" the forward part of the trigger that catches the lower notch on the bottom of the trigger?

or is the actual notch on the bottom of the hammer called the sear?

Here is what I've been reading so you can get an idea of the terminology.

http://www.notpurfect.com/main/fullauto.htm

badicedog
10-08-2008, 4:57 AM
look up M16 function or operation in youtube. It has an old army video that shows exactly what you are looking for. It shows a cut cross-section of the m16 internals. Hope that helps.

badicedog
10-08-2008, 5:53 AM
here's the link...
http://www.youtube.com/watch?v=5ui288P4pGU

ar15barrels
10-08-2008, 8:47 AM
turns out that it looks like the trigger actually has a extension that goes forward and that engages the sear notch on the hammer. and that releases the hammer when you pull the trigger. does this sound right?

Yes.

the actual notch on the bottom of the hammer is called the sear.
The trigger releases the sear surface which is on the hammer in semi-auto mode.
In full auto mode, the carrier releases the sear, which pivots in the reciever and retains the hammer whilst the trigger is held back by the finger, leaving the trigger out of the equation.

DDRH
10-08-2008, 10:01 AM
3 round burst would be nice...:D

TonyM
10-08-2008, 10:13 AM
Steve O,

Just to be clear, you are aware that you can't legally make one of you OLL Full Auto and that there is a date restriction on machine guns, right?

Pryde
10-08-2008, 12:01 PM
3 round burst would be nice...:D

3 round burst freaking sucks and the burst ratchet/sear mechanism makes the trigger pull of the M16 terrible.

Its a stupid feature that was only implemented because the bean counters in charge didn't want Soldiers and Marines wasting ammo and didn't want to spend the time and money training them to effectively fire controlled short bursts.

ke6guj
10-08-2008, 12:10 PM
Steve O,

Just to be clear, you are aware that you can't legally make one of you OLL Full Auto and that there is a date restriction on machine guns, right?
He is aware. We've been talking in another thread about registered receiver MG's, Registered Drop In Auto Sears, and Lightning Links for when he moves to NV.

PIRATE14
10-08-2008, 12:52 PM
It's a TRAP..............:D

ar15barrels
10-08-2008, 12:54 PM
It's a TRAP..............:D

http://i67.photobucket.com/albums/h303/usa732/its-a-trap.jpg

TonyM
10-08-2008, 3:02 PM
He is aware. We've been talking in another thread about registered receiver MG's, Registered Drop In Auto Sears, and Lightning Links for when he moves to NV.


Cool, you never know. It doesn't help that the laws are deliberately confusing.

Steve O
10-08-2008, 4:04 PM
here's the link...
http://www.youtube.com/watch?v=5ui288P4pGU

wow that is a nice vid! Thanks a lot that answers all my questions.

See the confusing part is I believe, in the video they mention that the hammer is released form the cocked position by the "nose of the trigger" in semi auto mode.

Well form what I have been hearing is the "Nose of the trigger" being referred to as the "sear"

Is this correct? Or am I wrong?

ar15barrels
10-08-2008, 4:09 PM
Well form what I have been hearing is the "Nose of the trigger" being referred to as the "sear"

In semi-auto, there really is no seperate "sear" like in some guns.
There are "sear surfaces" on the hammer and trigger though.

Steve O
10-08-2008, 4:17 PM
Steve O,

Just to be clear, you are aware that you can't legally make one of you OLL Full Auto and that there is a date restriction on machine guns, right?

Ohh yes! lol.

I've been chatting about FFL/NFA restrictions, and legal forms and such on my thread here.

http://www.calguns.net/calgunforum/showthread.php?p=1598385#post1598385


See that all started when I was looking for property in NV. The real-estate agent said the property was a nice location for toys, when I inquired about "toys" he went on to mention that he and his wife were both owners of M16 and explained to me that "if you are a square citizen, with no criminal convictions, you can buy a legal machine gun!" I was astonished!

I'm CA native, and like most people born an raised in California by hippie parents, I was thought that machine guns kill people, and that they are illegal!
But sense then I have come to realize that with the current political situation, gun rights may soon be infringed upon again. I would have never thought of my self as wanting a AW or MG, but when they went off the shelf's under Clinton, I became aware that the ban creates the demand!

And after studying the situation I realize that MG's are commodities, limited in numbers, and soon they could be worth a whole lot more!

I figure in the future, my classic cars won't run on junk gas, and machine guns will be triple what they are right now!
So I'm selling my classic cars, and trading them for legal machine guns. lol. This is after I complete my move to a free state!

Steve O
10-08-2008, 4:23 PM
Cool, you never know. It doesn't help that the laws are deliberately confusing.

Yea tell me about it!

The laws are so bad, I assumed all those on other boards talking about machine guns, lighting links, and auto sears were all a bunch of criminals.

I was afraid to ask them about any of the laws, but here on this board, I've been reading for quite some time now, and everyone here seems informative and lawful.

All around a good community, and I appreciate everyones help!

Steve O
10-08-2008, 4:28 PM
In semi-auto, there really is no seperate "sear" like in some guns.
There are "sear surfaces" on the hammer and trigger though.

yea, and i kept getting confused when someone would mention the "sear" in the semi-auto, because I related the sear as in "auto sear" in a conversion, or m16 and that spooked me!. lol.

DDRH
10-09-2008, 7:03 AM
3 round burst freaking sucks and the burst ratchet/sear mechanism makes the trigger pull of the M16 terrible.

Its a stupid feature that was only implemented because the bean counters in charge didn't want Soldiers and Marines wasting ammo and didn't want to spend the time and money training them to effectively fire controlled short bursts.

That's a bummer...well i've never tried so i can't say...i like the idea though. I've also heard the 3rnd Burst on the HK G3 is a much better design than the M16...true??

ke6guj
10-09-2008, 10:08 AM
I've also heard the 3rnd Burst on the HK G3 is a much better design than the M16...true??

I've heard that as well. Something about the M16's burst cam not resetting back to "zero" after you pull the trigger and do a partial burst. So, if you were quick on the trigger and did a 2-round burst, you next burst would only be 1-round, because 2 + 1 = 3, and you just "finished" the 3-round burst. Have to pull the trigger again for a new burst.

Other designs reset the burst mechanism so that every time you release the trigger, you will always have a full burst available, no matter how many shots happened on the last burst.

DDRH
10-09-2008, 10:30 AM
I've heard that as well. Something about the M16's burst cam not resetting back to "zero" after you pull the trigger and do a partial burst. So, if you were quick on the trigger and did a 2-round burst, you next burst would only be 1-round, because 2 + 1 = 3, and you just "finished" the 3-round burst. Have to pull the trigger again for a new burst.

Other designs reset the burst mechanism so that every time you release the trigger, you will always have a full burst available, no matter how many shots happened on the last burst.

Yes, that's what i've heard also...kinda wish M16's had that.


3 round burst freaking sucks and the burst ratchet/sear mechanism makes the trigger pull of the M16 terrible.

Its a stupid feature that was only implemented because the bean counters in charge didn't want Soldiers and Marines wasting ammo and didn't want to spend the time and money training them to effectively fire controlled short bursts.

Can you explain how the trigger is "terrible"? is the trigger pull heavier/lighter?

My AR trigger feels pretty heavy, but there's a crisp break.

I'm still very new to firearms...so not much experience with trigger feel.

how does it compare to a 2 stage trigger?

do M16's have single stage triggers? or will the military use 2stage triggers? or only 2 stage triggers used for accuracy type rifles...ie sniper rifles...or i think SPR type rifles? i think...

thanks for any info.

:confused:

6172crew
10-09-2008, 12:32 PM
When I moved to NV from CA the first thing I did was SBR a Ps90, the second one was a Mini Uzi and 2 silencers, then the M16 RR.

If you want to know how it works or if you have questions about anything just ask me...been there done that.

In NV your DL gets handed to you the same day so you are ready to buy firearms the same day you give up your CA DL.

There is no $200 stamp when a NFA item is transfered from dealer to dealer but if you buy a NFA item from a PP guy in another state you will have to do 2 transfers, One to your dealer then one to you.

If you buy C&R NFA and you have the C&R you dont go through a FFL.(if the item is in the same state). If you ae making a SBR, SBS, AOW, DD, Silencer you dont have to go through a FFL, these are done on a Form1 which you are the manufacture (my Ps90 has my name engraved on the side).

The stamp(it really is a stamp btw) doesnt have to be with you and a copy of it should be with you title 2 stuff but you dont have to show it to anyone cept the tax guys.

On a side note after I got the FA Uzi I walked up to the firing line and let loose a 32 round mag dump hoping some guy would run over and ask me if the Uzi was legal but 2k rounds plus and not even one person has blinked an eye when I go to the Carson dumps with my title 2 toys.:confused:

About the only thing I had was when I was shooting my SPR with a can on it and a guy walked over and said "man that silencer really works well doesnt it":D

The M16 is the most desired machine gun right now because of the multi cal platform, the only real factory M16s were done by Colt and the rest were converted by someone else. I have a Frankford Ar. RR because that was what I could afford.

ke6guj
10-09-2008, 1:44 PM
If you buy C&R NFA and you have the C&R you dont go through a FFL.(if the item is in the same state). Actually, even if the C&R NFA item is out of state, it doesn't have to go through an FFL if you are an C&R FFL and can be received directly to you. That is because YOU are the FFL. However, be aware that C&R NFA stuff has an extra premium because of this fact, and that some states only allow NFA ownership of C&R MGs. So, those guys are willing to pay extra to get it.

trinydex
10-09-2008, 2:16 PM
here's the link...
http://www.youtube.com/watch?v=5ui288P4pGU

wow that's really well done. surprised there isn't something like that that is updated with 3d models on youtube. there's only a very short snippet of one, but no explanations.