AR-15 M16 Triggers, Legality and Availability?

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Frost Cracked

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Hello,

I'm considering venturing into the AR world this year... and had a question regarding M16 trigger groups. A friend at the range had an older AR-15, that had a select-fire trigger group. It was NOT capable of full-auto, but did have a 3 point switch. Thinking this rather neat, I was curious about their status, as I know a few other military style firearms can have 'show' selectors available.

Are they legal? Searches on CGN have said either here or there on them....

Can I buy one? I saw a few sites that had them listed, but seem to be out of stock. Were they just sort of a thing that came in once, and then that was it? If so, where would I look?

-Thanks
 
If you are going to install the F/A fire control group parts in your AR lower, make sure you don't also have a F/A bolt carrier in your upper, or it WILL "go fast"!
 
76r said:
If you are going to install the F/A fire control group parts in your AR lower, make sure you don't also have a F/A bolt carrier in your upper, or it WILL "go fast"!
Click to expand...

He wouldn't be able to install the auto sear (assuming there is no DIAS cuz they are illegal). So anything it would do with a F/A carrier at that point, it would do with a S/A carrier as well.

It wouldn't fire F/A reliably without an auto sear, the hammer would end up riding the carrier home
 
76r said:
If you are going to install the F/A fire control group parts in your AR lower, make sure you don't also have a F/A bolt carrier in your upper, or it WILL "go fast"!
Click to expand...
No it won't.
You still need the FA sear which is not legal to install and requires the auto sear hole drilled into the receiver.
You can have all the other parts there as it still is semi auto only.
 
Not true.
The sear only releases the hammer in time with the bolt to ensure the bolt is in battery.
The selector causes the disconnector NOT to lock the hammer back in place as normally happens in semi position.
When you hold the trigger down for a second consecutive shot with in semi, the hammer is still caught by the hook of the disconnector, and is not able to follow the carrier 'home' to hit the firing pin. On F/A position the sector pushes the tail of the disconnector down which rotates the upper hook of the disconnector back out of the way so it can't grab the hook of the hammer, which is being pushed back by the carrier. The hammer is then held back by the bottom of the carrier and WILL follow the bolt carrier back as it travels foreward again.
(yes, I know I can't spell disconnector)
 
Still wrong!
The auto sear is tripped by the bcg when safely in battery which in turn releases the hammer !
 
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76r said:
Not true.
The sear only releases the hammer in time with the bolt to ensure the bolt is in battery.
The selector causes the disconnector NOT to lock the hammer back in place as normally happens in semi position.
When you hold the trigger down for a second consecutive shot with in semi, the hammer is still caught by the hook of the disconnector, and is not able to follow the carrier 'home' to hit the firing pin. On F/A position the sector pushes the tail of the disconnector down which rotates the upper hook of the disconnector back out of the way so it can't grab the hook of the hammer, which is being pushed back by the carrier. The hammer is then held back by the bottom of the carrier and WILL follow the bolt carrier back as it travels foreward again.
(yes, I know I can't spell disconnector)
Click to expand...

...and the hammer will ride the bolt home. It will most likely not have enough inertia to cause the firing pin to detonate the primer and you will be left with a rifle that is de-cocked with a round in the chamber. That's it. There is a SLIGHT possibility of detonating the primer this way, but even if it did happen, you'd have an out of battery detonation.

In a closed bolt system, you can't have F/A without an F/A sear/trip lever of some sort.
 
Armafield said:
Still wrong!
The auto sear is tripped by the bcg when safely in battery which in turn releases the disconnector!
Click to expand...

Think about it.
If there is NO sear, does your action stay open? NO. The bolt will start it's return, followed by the hammer which has NOT been held locked because the disconnector is NOT holding it back, because the selector has pushed it's 'tail' down. There is a reason for those funny little differences between semi and F/A parts.
Look at a blueprint and you can quite easily see the how everything works. It's a very simple design.
 
Walther_PPK said:
...and the hammer will ride the bolt home. It will most likely not have enough inertia to cause the firing pin to detonate the primer and you will be left with a rifle that is de-cocked with a round in the chamber. That's it. There is a SLIGHT possibility of detonating the primer this way, but even if it did happen, you'd have an out of battery detonation.

In a closed bolt system, you can't have F/A without an F/A sear/trip lever of some sort.
Click to expand...

Yes, you do risk and out of battery detonation-but not guarantee such an event. IF all goes well you will empty your clip with one squeeze of the trigger - untimed F/A! As I mentioned above.
I have seen it (obviously in the US though).
 
76r said:
Think about it.
If there is NO sear, does your action stay open? NO. The bolt will start it's return, followed by the hammer which has NOT been held locked because the disconnector is NOT holding it back, because the selector has pushed it's 'tail' down. There is a reason for those funny little differences between semi and F/A parts.
Look at a blueprint and you can quite easily see the how everything works. It's a very simple design.
Click to expand...
I don't think your seeing the blueprint correctly!
When rotated to full auto the second sear is completely removed from the equation, it is the hammer hook that is engaged by the auto sear and the little tab is tripped by the rear of the BCG causing the hammer to fall when safely in battery!
 
Armafield said:
I don't think your seeing the blueprint correctly!
When rotated to full auto the second sear is completely removed from the equation, it is the hammer hook that is engaged by the auto sear and the little tab is tripped by the rear of the BCG causing the hammer to fall when safely in battery!
Click to expand...

Don't get hung up on the sear. Work thru it without the sear and you will see the function.
I argued with someone until I was blue in the face. He then showed me with his registered F/A lower (in US remember). Then removed the sear and fired it. It emptied a 10 rd clip pretty fast!
 
Upon release of the hammer the Bolt is in battery, that's the job of the cam pin. When locked up tight that's when you would want a detonation!
Being a military firearm I don't believe they would want a grey area concerning their main rifle system!
 
76r said:
Don't get hung up on the sear. Work thru it without the sear and you will see the function.
I argued with someone until I was blue in the face. He then showed me with his registered F/A lower (in US remember). Then removed the sear and fired it. It emptied a 10 rd clip pretty fast!
Click to expand...

I'm not getting hung up on the sear! It is actually the hammer!
If the sear is removed what does the FA BCg have to do with what you stated in your original post?
BTW you friend down south had a faulty and dangerous firearm I hope he's doing alright with his clips and all!
 
76r said:
If you are going to install the F/A fire control group parts in your AR lower, make sure you don't also have a F/A bolt carrier in your upper, or it WILL "go fast"!
Click to expand...

No. It won't....
I have had everything installed. FA bolt carrier and complete FA trigger set from a batch of M16 surplus kits irunguns brought in years ago (minus the sear obviously and a lower that would even mount it). I installed the FA USGI trigger set in my restricted commercial semi auto Armalite lower. The selector would go to the auto setting and fire one round. Keep in mind I also had an old Colt FA bolt carrier on my rifle/upper.

You end up with a live round in the chamber and a dead trigger ie you have to manually #### it and eject the live cartridge in the chamber to chamber another cartridge/#### the hammer again then you pull the trigger and repeat etc
It WILL NOT go full auto unless you have a FA lower and the complete auto sear installed in it to delay the hammer. Without the sear holding the hammer to delay it/and the bolt to trip the sear later in the bolt travel sequence, the hammer will simply follow the bolt forward as it rides over the hammer in a semi auto lower. It does not strike the firing pin, it merely rides up and rests on it. It happens fast but in all the shooting I did with many different types of ammunition it never once went full auto.

Stop spreading misinformation based on lack of mechanical understanding of the firearm and creating pointless panic for nothing please.....

Also as an addition it is literally impossible to have an out of battery initiation of a cartridge in the AR15 design. You can quote the technical specifications and design of Stoner himself for that. The hammer cannot be released to strike the cartridge primer with enough inertia/force to fire it until the bolt is fully forward and engaged in the locking lugs of the barrel extension. This is also the same reason you can't fire full auto in a semi auto lower with a FA bolt and FA trigger set (minus the sear installed obviously) The hammer is released by the sear in a true full auto M16 just before it is locked in full battery, it is timed so that the back of the bolt trips the sear and the hammer is released a millisecond before the bolt locks in the barrel extension, the hammer has to travel the full distance in order to strike and actually initiate the primer. It is released as the bolt is still moving forward but it is timed so that the bolt will be fully locked and the hammer falls with full force thanks only to the sear timing this to precision. The bolt clears the hammer and is locked in battery just before the hammer travels the full unimpeded distance and does what it's supposed to do.
 
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To elaborate on what Travis said, the firing pin can not protrude from the bolt face until the bolt has rotated fully to the lock position and started to retract into carrier.

Ie, out of battery ignition wont happen
 
Armafield said:
Upon release of the hammer the Bolt is in battery, that's the job of the cam pin. When locked up tight that's when you would want a detonation!
Being a military firearm I don't believe they would want a grey area concerning their main rifle system!
Click to expand...

But ONLY because the sear times it correctly.
 
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