AR-15 trigger system behavior

divil · November 9, 2011, 10:05 PM

Hi, I have a question about an AR-15 trigger: if you take off the upper, and cock the hammer by hand, then pull the trigger, let the hammer fall, and reset the hammer by hand, and you feel it engage the sear, but, you can make it fall again upon trigger reset, by just exerting a little pressure on the hammer from behind...that's not correct, right? Could that cause the rifle to fire doubles? I am guessing that no amount of pressure from behind should allow the hammer to fall until the trigger is first released and then pulled again?

1Hobie · November 9, 2011, 11:49 PM

Maybe you're not truly simulating the behaviour of the FCG under normal operating conditions. Are you fully seating the hammer or are you just pulling it back until it clicks? That hammer gets slapped back hard when the bolt cycles. BTW, don't let the hammer hit the front of the lower, use a buffer of some sort.

Why are you concerned? Function problems? Doubles, slam fires, that sort of thing?

Regards,

Hobie

divil · November 10, 2011, 12:06 AM

Quote:

Maybe you're not truly simulating the behaviour of the FCG under normal operating conditions. Are you fully seating the hammer or are you just pulling it back until it clicks? That hammer gets slapped back hard when the bolt cycles. BTW, don't let the hammer hit the front of the lower, use a buffer of some sort.

Why are you concerned? Function problems? Doubles, slam fires, that sort of thing?

Well it might be doubles, or I might have been bump firing. It is a rare occurance. So I am checking for malfunctions. I was advised to test it by firing, then resetting the hammer manually and making sure it clicks in to place, and stays there when I release the trigger.

The thing is, that I can test it like this all day and the hammer will never double. But, I just discovered when taking a second look today, that if I press gently on the hammer from behind - just a little pressure is all it takes - then the releasing of the trigger will drop the hammer. Now, if I re-cock the hammer, then release the trigger, and then apply the pressure - nothing. But if the pressure is there as I release the trigger - the hammer drops. When I cock the hammer BTW I'm pushing it back as hard as I can with my fingers.

I've been advised that the company I bought the trigger kit from (Del-Ton) have a reputation for poor quality trigger components. Could this be the cause of what looked like doubles?

PS I am catching the hammer with my hand to prevent damage when I 'fire', thanks for the heads up.

CowTowner · November 10, 2011, 08:13 AM

If it's so easy for the hammer to move forward, then I would suggest that you have a trigger group issue and it needs to be looked at by a gunsmith.
Why? To cover yourself legally. If it is in fact a physical malfunction due to poorly produced parts, then the gun should be repaired/parts replaced.
Don't take it to a public range where you don't know who is watching.

divil · November 10, 2011, 09:33 AM

Yep I definitely wouldn't fire it like this - but I just wanted to check, since I still didn't know if this is a malfunction, or if they all work this way. Thanks.

Poodleshooter · November 10, 2011, 11:45 AM

When you test the AR fire control components, keep your trigger finger pulled all the way back while you manually reset the hammer. It isn't the "sear" catching the hammer at that point, it's the disconnector: the little claw piece mounted in the middle of the trigger. When you release the trigger, the disconnector releases the hammer to be caught on the nose of the trigger (the closest thing the AR has to a "sear").
If sear engagement in the AR is inadequate/marginal, the AR will fire again when you release the trigger, as the disconnector will release the hammer, but the trigger nose/sear will not catch it, allowing the hammer to move forward fully, firing the weapon again.
This is what often causes intermittent doubling.

divil · November 10, 2011, 12:21 PM

Poodleshooter that makes sense, thanks. I have heard of this happening, but in my case, I'm just not sure if that is exactly what's happening. When I'm applying the pressure I talked about to the hammer, at that point I suppose it's still on the disconnector. Then I release the trigger, and the hammer drops. But if I don't push the hammer forwards while releasing the trigger, it will catch where it's supposed to every time. So I can't tell if that's a problem with the trigger/sear, or the disconnector, or the hammer. Anyway I am replacing the whole thing with a drop in system so that should take care of it. I'll contact the supplier of the original parts to see if they will take them back.

Poodleshooter · November 11, 2011, 12:03 PM

If you can manually push the hammer off of the disconnector by simply pushing the hammer forward then either something is wrong with the disconnector hook angle (ground/worn down perhaps?)or the entire disconnector is canted backwards with respect to the trigger. This may be a disconnector spring problem. A freely moving disconnector with a missing spring might be able to release the hammer without the trigger going forward (bad).The disconnector should only release the hammer when the trigger is released. It should firmly hold the hammer while the trigger is fully pulled to the rear.

divil · November 11, 2011, 12:21 PM

Quote:

If you can manually push the hammer off of the disconnector by simply pushing the hammer forward then either something is wrong with the disconnector hook angle

Nope I can't do that. No amount of just pushing will release the hammer - it's the combination of pushing the hammer and releasing the trigger that causes the hammer to fall.

Quote:

(ground/worn down perhaps?)

Definitely not. The parts were bought new and the rifle has not been fired much. The only possibilities I can think of are either that the parts were defective/out of spec or I installed them incorrectly.

Quote:

The disconnector should only release the hammer when the trigger is released. It should firmly hold the hammer while the trigger is fully pulled to the rear.

Well it is doing the above perfectly. As long as I hold the trigger back, the hammer won't fall. Furthermore, if I simply release the trigger, the hammer will not fall. But, if I release the trigger while pressing gently on the hammer from behind, then the hammer will fall. Only a small amount of pressure is needed - I have found a threshold of pressure that will reliably cause this behavior. I am trying to understand if this is a malfunction or not.

divil · November 11, 2011, 08:53 PM

Just finished installing my new trigger system. I used the Timney drop in trigger. Crazy money but I had to get this sorted with the minimum hassle, so I went ahead and bought it.

The old one must have been bad because the new trigger does not exhibit the behavior I described above. Pressing the hammer from behind has no effect when I release the trigger.

Not only is the new trigger far higher quality, but the safety now engages much more positively, and is much tighter. It always felt a bit rattly before.

I can't see anything obviously wrong with the old components, but then I wouldn't really know what to look for. So I'll send them back to Del-Ton.

Thanks for the input everyone.

divil · November 24, 2011, 06:47 PM

Just tested the rifle with the new trigger. I fired about 20 rounds slow fire, and then 60 fairly rapidly - no problems whatsoever. The Timney trigger is pretty good too. I have the 4lb one which is not that light but there is no creep whatsoever.

Anyway, a few days ago Del-Ton called and said they received the bad trigger parts I sent back but they couldn't reproduce the problem. So they're going to send new parts anyway. I'll probably never fit them now that I have a much higher quality trigger in there. Thanks for the help.

November 9, 2011, 10:05 PM	#1
divil Senior Member Join Date: November 11, 2009 Posts: 506	AR-15 trigger system behavior Hi, I have a question about an AR-15 trigger: if you take off the upper, and cock the hammer by hand, then pull the trigger, let the hammer fall, and reset the hammer by hand, and you feel it engage the sear, but, you can make it fall again upon trigger reset, by just exerting a little pressure on the hammer from behind...that's not correct, right? Could that cause the rifle to fire doubles? I am guessing that no amount of pressure from behind should allow the hammer to fall until the trigger is first released and then pulled again?

November 10, 2011, 08:13 AM	#4
CowTowner Senior Member Join Date: October 17, 2007 Location: Cowtown of course! Posts: 1,747	If it's so easy for the hammer to move forward, then I would suggest that you have a trigger group issue and it needs to be looked at by a gunsmith. Why? To cover yourself legally. If it is in fact a physical malfunction due to poorly produced parts, then the gun should be repaired/parts replaced. Don't take it to a public range where you don't know who is watching. __________________ NRA Chief Range Safety Officer, Home Firearms Safety, Pistol and Rifle Instructor *“Today, we need a nation of Minutemen, citizens who are not only prepared to take arms, but citizens who regard the preservation of freedom as the basic purpose of their daily life......”* President John F. Kennedy

November 24, 2011, 06:47 PM	#11
divil Senior Member Join Date: November 11, 2009 Posts: 506	wrapping up... Just tested the rifle with the new trigger. I fired about 20 rounds slow fire, and then 60 fairly rapidly - no problems whatsoever. The Timney trigger is pretty good too. I have the 4lb one which is not that light but there is no creep whatsoever. Anyway, a few days ago Del-Ton called and said they received the bad trigger parts I sent back but they couldn't reproduce the problem. So they're going to send new parts anyway. I'll probably never fit them now that I have a much higher quality trigger in there. Thanks for the help.

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November 9, 2011, 11:49 PM	#2
1Hobie Senior Member Join Date: November 6, 2010 Location: west central Illinois Posts: 277	Maybe you're not truly simulating the behaviour of the FCG under normal operating conditions. Are you fully seating the hammer or are you just pulling it back until it clicks? That hammer gets slapped back hard when the bolt cycles. BTW, don't let the hammer hit the front of the lower, use a buffer of some sort. Why are you concerned? Function problems? Doubles, slam fires, that sort of thing? Regards, Hobie

November 10, 2011, 09:33 AM	#5
divil Senior Member Join Date: November 11, 2009 Posts: 506	Yep I definitely wouldn't fire it like this - but I just wanted to check, since I still didn't know if this is a malfunction, or if they all work this way. Thanks.

November 10, 2011, 11:45 AM	#6
Poodleshooter Senior Member Join Date: August 7, 2000 Location: Floating down the James River in VA Posts: 2,599	When you test the AR fire control components, keep your trigger finger pulled all the way back while you manually reset the hammer. It isn't the "sear" catching the hammer at that point, it's the disconnector: the little claw piece mounted in the middle of the trigger. When you release the trigger, the disconnector releases the hammer to be caught on the nose of the trigger (the closest thing the AR has to a "sear"). If sear engagement in the AR is inadequate/marginal, the AR will fire again when you release the trigger, as the disconnector will release the hammer, but the trigger nose/sear will not catch it, allowing the hammer to move forward fully, firing the weapon again. This is what often causes intermittent doubling.

November 10, 2011, 12:21 PM	#7
divil Senior Member Join Date: November 11, 2009 Posts: 506	Poodleshooter that makes sense, thanks. I have heard of this happening, but in my case, I'm just not sure if that is exactly what's happening. When I'm applying the pressure I talked about to the hammer, at that point I suppose it's still on the disconnector. Then I release the trigger, and the hammer drops. But if I don't push the hammer forwards while releasing the trigger, it will catch where it's supposed to every time. So I can't tell if that's a problem with the trigger/sear, or the disconnector, or the hammer. Anyway I am replacing the whole thing with a drop in system so that should take care of it. I'll contact the supplier of the original parts to see if they will take them back.

November 11, 2011, 12:03 PM	#8
Poodleshooter Senior Member Join Date: August 7, 2000 Location: Floating down the James River in VA Posts: 2,599	If you can manually push the hammer off of the disconnector by simply pushing the hammer forward then either something is wrong with the disconnector hook angle (ground/worn down perhaps?)or the entire disconnector is canted backwards with respect to the trigger. This may be a disconnector spring problem. A freely moving disconnector with a missing spring might be able to release the hammer without the trigger going forward (bad).The disconnector should only release the hammer when the trigger is released. It should firmly hold the hammer while the trigger is fully pulled to the rear.

November 11, 2011, 08:53 PM	#10
divil Senior Member Join Date: November 11, 2009 Posts: 506	Just finished installing my new trigger system. I used the Timney drop in trigger. Crazy money but I had to get this sorted with the minimum hassle, so I went ahead and bought it. The old one must have been bad because the new trigger does not exhibit the behavior I described above. Pressing the hammer from behind has no effect when I release the trigger. Not only is the new trigger far higher quality, but the safety now engages much more positively, and is much tighter. It always felt a bit rattly before. I can't see anything obviously wrong with the old components, but then I wouldn't really know what to look for. So I'll send them back to Del-Ton. Thanks for the input everyone.