View Full Version : Suppressor causing my AR to fire bursts and fail to reset
This is a relatively new Colt Mk18 upper on an LE6920 lower. Everything is stock except the trigger, which I replaced with a Geissele Super Dynamic. I think it probably has about a thousand rounds through it total.
I had put several hundred rounds through it without any issues and then all of the sudden now it's firing two and three round bursts and failing to reset. I tried a good thorough cleaning first of all, and that didn't help. I took out the trigger and thoroughly cleaned and inspected everything and don't see any problems there. Passes dry fire function checks with no problem.
I've also tried different buffers and ammo to no avail. This includes an H3, so I don't think the bolt is going too fast. It's having no problems picking up rounds or locking back on empties.
What I discovered today is that with a suppressor on it, seemingly any suppressor, that's what appears to be causing the issue. No suppressor, no issue.
Prior to this thing developing out of the blue though, it never gave me any issues no matter what. I had used different buffers, steel ammo, suppressed, unsuppressed, rapid fire...no issues anywhere.
Sitting here scratching my head how this could just develop out of the blue on a relatively new gun, and why the suppressor would aggravate the issue. I say aggravate and not cause because it ran for many rounds just fine with suppressors on it, so I don't think that's the root of the issue.
I think it's a spring in the FCG. Without the suppressor, carrier speed is low enough to not cause an issue. But add the suppressor the carrier speed is increased enough to overcome the action of the marginal spring. Probably the semi-auto sear spring.
I have no idea, but I would ask Geissele if they have any thoughts. I also would put another trigger in it and see if it persist. Maybe narrow down the issue if its the trigger.
PB
I think it's a spring in the FCG. Without the suppressor, carrier speed is low enough to not cause an issue. But add the suppressor the carrier speed is increased enough to overcome the action of the marginal spring. Probably the semi-auto sear spring.
That's what I was thinking, too. Sucks though since it's a brand new trigger (practically speaking). What's more, it's a coaxial type pass through silencer with almost no back pressure, and I tried slowing the bolt down with an H3 buffer to see if excessive bolt velocity is the culprit. I don't think it's too excessive since it's not ejecting too bad.
That's what I was thinking, too. Sucks though since it's a brand new trigger (practically speaking). What's more, it's a coaxial type pass through silencer with almost no back pressure, and I tried slowing the bolt down with an H3 buffer to see if excessive bolt velocity is the culprit. I don't think it's too excessive since it's not ejecting too bad.
Ignore ejection angle. It has nothing to do with your problem.
It's possible the semi-auto sear spring was damaged during installation.
Even with a coaxial suppressor, gas drive needs to be correct. I don't know what your upper is, but it could be overgassed without the suppressor.
This is not uncommon, and the first thing I was going to ask if you didn’t specify in your post would be what trigger you installed.
You are bump firing with the lighter trigger and increased recoil of the suppressor.
This is not uncommon, and the first thing I was going to ask if you didn’t specify in your post would be what trigger you installed.
You are bump firing with the lighter trigger and increased recoil of the suppressor.
The silencer actually reduces recoil by a lot. Probably half or more. I thought I was bump firing too at first, but then after deliberately holding down the trigger I realized that's not what was happening.
Also, the trigger is now failing to reset, which is new. First it was just firing bursts, and now every like fifth round maybe it's failing to reset.
And there's also the fact that I fired hundreds of rounds through it, suppressed, with zero issues, with this same trigger.
Reminds me of this earlier thread.
https://www.m4carbine.net/showthread.php?232126
There was a thread like this on reddit earlier this week. It sounded as if the dude was having hammer follow causing a burst, with the failure to reset issue being caused by a light strike due to the hammer follow catching it not quite in battery. He also had a G trigger, I think.
Bump firing would be plausible, but it sounds like you ruled that out.
I have no idea why your suppressor would be causing it.
There was a thread like this on reddit earlier this week. It sounded as if the dude was having hammer follow causing a burst, with the failure to reset issue being caused by a light strike due to the hammer follow catching it not quite in battery. He also had a G trigger, I think.
Bump firing would be plausible, but it sounds like you ruled that out.
I have no idea why your suppressor would be causing it.
Yea I've been doing some googling and it seems like lots of people with Geissele triggers are having this issue. Seems like hammer follow is the issue. Seriously thinking about just ditching the Geissele trigger and going back to the milspec one. This is just ridiculous.
One possible issue might be the 22 conversion kit I've been using. I can't really verify, but apparently people are saying that those break Geissele hammers. My hammer doesn't show any visible damage, but who knows.
Which SD trigger are you running? SD-3G, SD-E, SD-C? The 3G is touchy by design and I ended up selling mine off. I have several SD-Cs and SD-Es with no issues to include in 9mm and .22 builds.
Good Luck!
Dennis.
Sent from my SM-N975U using Tapatalk
Yea I've been doing some googling and it seems like lots of people with Geissele triggers are having this issue. Seems like hammer follow is the issue. Seriously thinking about just ditching the Geissele trigger and going back to the milspec one. This is just ridiculous.
Consider the LaRue MBT-2S. It has a rather long reset but a very nice break. I have not read of any problems with it other than one member here who found it would not fit the trigger pocket of his receiver. He did not appreciate the dismissive response he got from Mark LaRue but I don't believe he measured the trigger either.
Are you, by chance, using anti-rotation pins in your FCG?
polydeuces
11-24-21, 10:35
'Good' to see this happened to someone else as well.
Zeroing my new 13.5 .308 upper with a 10" F1 can, Geissele SSA trigger, VLTOR A5 (for ar10), everything else stock.
10 round mag loaded with 5 rounds Federal Sierra 168 bthp. Geissele SSA trigger.
Broke the shot and HOLY CRAP WTF was that???!!! Took me a few seconds to comprehend what happened - I just experienced a full auto burst.
Still haven't figured out how that happened and have not used that particular can on that upper again.
Has not repeated with my other can (F1 w different internal design.
Be happy to hear some ideas.
Are you, by chance, using anti-rotation pins in your FCG?
Nope.
Bump fire.
I considered that, but it doesn't explain why it didn't do it for the first like 500 rounds, and why it got progressively worse over time.
Oh, and the cyclic rate is way high. Much higher than I think an accidental bump fire is capable of. It also doesn't have that variable cyclic rate that bump fire does. It's just zip and it's gone.
'Good' to see this happened to someone else as well.
Zeroing my new 13.5 .308 upper with a 10" F1 can, Geissele SSA trigger, VLTOR A5 (for ar10), everything else stock.
10 round mag loaded with 5 rounds Federal Sierra 168 bthp. Geissele SSA trigger.
Broke the shot and HOLY CRAP WTF was that???!!! Took me a few seconds to comprehend what happened - I just experienced a full auto burst.
Still haven't figured out how that happened and have not used that particular can on that upper again.
Has not repeated with my other can (F1 w different internal design.
Be happy to hear some ideas.
Yea it seems to be pretty common if you do some googling. I tried multiple suppressors and they all do it.
Yea it seems to be pretty common if you do some googling. I tried multiple suppressors and they all do it.
It sounds like the disconnector spring is getting weak, and the suppressors might be increasing the carrier velocity enough to make it overrun the weak spring. Maybe.
It sounds like the disconnector spring is getting weak, and the suppressors might be increasing the carrier velocity enough to make it overrun the weak spring. Maybe.
That's what others have suggested, and sounds pretty reasonable. Problem is, the trigger only has like maybe 1500 rounds on it tops. Proly closer to 1000. Only thing I can figure is the 22 conversion I was using killed it. But I checked, and the manufacturer doesn't warn against them. Or 9mm for that matter, which is way more severe even.
You can try swapping in a spring from another FCG, and see what happens.
What happened when you swapped out the disconnector spring, or replaced the entire fire control group?
What happened when you swapped out the disconnector spring, or replaced the entire fire control group?
I don't know yet. It's on its way.
Does it use a standard spring? The thought of it being unique to the trigger never crossed my mind. I went to Geissele's site to see if they have springs for sale, but didn't see any. I did see the % off for the upcoming sale....which will probably cause me to get another.
I considered that, but it doesn't explain why it didn't do it for the first like 500 rounds, and why it got progressively worse over time.
You ruled out bump fire, so your trigger should go back to the manufacturer.
Accidentally bump firing is common enough with these very light triggers, more so suppressed, even more on a 308 like polydeuces above.
It’s the first thing that he needs to rule out.
You ruled out bump fire, so your trigger should go back to the manufacturer.
Accidentally bump firing is common enough with these very light triggers, more so suppressed, even more on a 308 like polydeuces above.
It’s the first thing that he needs to rule out.
Idk, the part I can't wrap my mind around is why it wouldn't do it at all for hundreds of rounds and then get progressively worse. If it did it straight out of the box or I had changed my shooting style or something I would assume bump fire.
The only thing I did that was a variable is I used my 22 conversion a lot lately. I'm pretty far out in the boondocks, but I still have neighbors like 300 yards away in one direction, so when I shoot at night I use the 22 conversion so as not to piss them off. I'm kind of nocturnal, so even suppressed I imagine shooting 223 in the middle of the night might still be audible in their houses.
polydeuces
11-25-21, 23:17
Bump fire.
Bump fire meaning it is a spring issue? (in that scenario)
Side note,
Suppressor design clearly is a lot of dark magic (science/art). Swapped can on that 13.5 upper and everything been running fine.
Adding a bunch of weirdness to this topic- the can causing the burst also had massive poi shift with that (13.5) barrel, yet with an 18" ran fine, tightening/shift groups by ~ .5 moa., no issues.
More 'voodoo' with shorter barrels (more back pressure)?
Bump fire meaning it is a spring issue? (in that scenario)
Side note,
Suppressor design clearly is a lot of dark magic (science/art). Swapped can on that 13.5 upper and everything been running fine.
Adding a bunch of weirdness to this topic- the can causing the burst also had massive poi shift with that (13.5) barrel, yet with an 18" ran fine, tightening/shift groups by ~ .5 moa., no issues.
More 'voodoo' with shorter barrels (more back pressure)?
If there's a weakness in the system, it's always going to show up with short barrels first. They're less forgiving.
You know, I just remembered something. I did experience failures to reset early on with the 22 conversion. I just assumed it was the dirty 22 residue gumming up the trigger, but in hindsight it wasn't THAT dirty. So it's possible, now that I think about it, that I've been having trouble since day one.
Idk, the part I can't wrap my mind around is why it wouldn't do it at all for hundreds of rounds and then get progressively worse. If it did it straight out of the box or I had changed my shooting style or something I would assume bump fire.
If you are sure it’s not bump firing then it it something wrong with the trigger, dirty to the point of obstructing disconnector movement, broken hammer pin, disconnector spring installed the wrong way, disconnector spring binding, burr or excessive wear on a sear surface...
Bump fire meaning it is a spring issue? (in that scenario)
Bump fire means the rifle is bouncing forward enough after recoil that the trigger runs into your trigger finger and fires.
To troubleshoot for this you need to pull the trigger pretty hard and consciously keep it pulled all the way to the rear through recoil.
If you are sure it’s not bump firing then it it something wrong with the trigger, dirty to the point of obstructing disconnector movement, broken hammer pin, disconnector spring installed the wrong way, disconnector spring binding, burr or excessive wear on a sear surface...
Bump fire means the rifle is bouncing forward enough after recoil that the trigger runs into your trigger finger and fires.
To troubleshoot for this you need to pull the trigger pretty hard and consciously keep it pulled all the way to the rear through recoil.
I could see it kind of sort of being that bump fire is maybe PART of the problem. My guess is that the hammer is often being caught not fully engaged with the sear surface and that a slight breeze could pull the trigger at that point.
Bump fire in my mind also doesn't really offer much explanation for the failure to reset, which is probably about every five rounds now. The issue began as occasional bursts, which became frequent, then the bursts began giving way to failures to reset, which are now the dominant problem.
In fact, with 5.56, failure to reset is now the only problem. I have not been able to get 5.56 to fire a burst like with 223.
I'm also not satisfied that bump fire could produce the rate of fire this thing is putting out, or the regular rate of fire. Bump fire, even when intentional, has that characteristic variable rate of fire. This is an extremely fast rate of fire, and has a very regular cadence.
I can get the rifle to bump fire if I hold it loosely and don't use the stock, but it has that characteristic variable rate of fire, and is slower than the random bursts I experience.
So it's really following the pattern of a worn out trigger that's extremely typical. Bursts that grow in frequency and duration, that eventually give way to only failures to reset within a few hundred rounds. Issue is, this trigger is practically brand new.
It's a mystery to me, so it's going back to the manufacturer, and it will be replaced with a milspec trigger that I've already ordered. I have one, or several lol, in my parts bins somewhere but finding it/them would be a major headache at this point, so I just ordered a new Colt trigger from Armsunlimited. Not looking forward to the grittiness, but I'm 99.9999% positive it's going to solve the issue and return my gun to its former glory.
Bump fire in my mind also doesn't really offer much explanation for the failure to reset
Hammer down but hasn’t fired? If the timing is off the hammer drops before the bolt is in battery or just follows it forward. Could be from a disconnector problem or bump fire, though it happens more from the disconnector failure in my experience.
Does it pass a function check?
Bump fire with a light+short reset match type trigger is often faster and more consistent than what you are used to with a more military style trigger.
Hammer down but hasn’t fired? If the timing is off the hammer drops before the bolt is in battery or just follows it forward. Could be from a disconnector problem or bump fire, though it happens more from the disconnector failure in my experience.
Does it pass a function check?
Bump fire with a light+short reset match type trigger is often faster and more consistent than what you are used to with a more military style trigger.
Seems like a really unlikely thing to happen like five times a mag. The timing would have to be absolutely perfect.
And my understanding of bump fire is that the inertia of the bolt going home drives the gun into the trigger finger, so it seems like by definition the bolt would have to be in battery to cause the bump fire? In which case I shouldn't be getting hammer follow?
tweakmeister
11-27-21, 10:11
I also saw this happen with a Brownells B-GRF and assume an S3G would do the same. The trigger reset fine unsuppressed and when the upper was removed (hand cycling the trigger).
Geissele said there are too many variables to warrant replacing it and that if it worked fine hand cycling then it should be okay. The engagement surfaces looked fine.
The weapon would occasionally burst while suppressed and continue going with the finger off the trigger then stop after a handful of rounds. The rate of fire was extremely high. Would love to see if there is a pattern here that would indicate how to repair it (heavier buffer?). Ultimately in this case the trigger was cheap enough that it was disposed to avoid further headaches.
https://photos.smugmug.com/photos/i-wNVRGdG/0/a6665ce6/cLHFHSxDpZjLwm3PHCVBGp98rcgwJbjRWPRcPjt5M-1638115742-O/i-wNVRGdG.jpg
You see that spring in the photo, just above the G and the E? Remove it and install a new replacement.
tweakmeister
11-27-21, 10:14
Thank you for the info. Is there an "enhanced" version of this spring sold by any manufacturer? What is the usual service life of this spring?
It looks like Geissele sells a replacement spring kit.
I could see it kind of sort of being that bump fire is maybe PART of the problem. My guess is that the hammer is often being caught not fully engaged with the sear surface and that a slight breeze could pull the trigger at that point.
Bump fire in my mind also doesn't really offer much explanation for the failure to reset, which is probably about every five rounds now. The issue began as occasional bursts, which became frequent, then the bursts began giving way to failures to reset, which are now the dominant problem.
In fact, with 5.56, failure to reset is now the only problem. I have not been able to get 5.56 to fire a burst like with 223.
I'm also not satisfied that bump fire could produce the rate of fire this thing is putting out, or the regular rate of fire. Bump fire, even when intentional, has that characteristic variable rate of fire. This is an extremely fast rate of fire, and has a very regular cadence.
I can get the rifle to bump fire if I hold it loosely and don't use the stock, but it has that characteristic variable rate of fire, and is slower than the random bursts I experience.
So it's really following the pattern of a worn out trigger that's extremely typical. Bursts that grow in frequency and duration, that eventually give way to only failures to reset within a few hundred rounds. Issue is, this trigger is practically brand new.
It's a mystery to me, so it's going back to the manufacturer, and it will be replaced with a milspec trigger that I've already ordered. I have one, or several lol, in my parts bins somewhere but finding it/them would be a major headache at this point, so I just ordered a new Colt trigger from Armsunlimited. Not looking forward to the grittiness, but I'm 99.9999% positive it's going to solve the issue and return my gun to its former glory.
Okie, I have Colt FCGs in all my Colts, sharp letoff, no creep, fast strong reset, no grit. I've got two SSAs, don't like them, don't use them, don't care.
I also saw this happen with a Brownells B-GRF and assume an S3G would do the same. The trigger reset fine unsuppressed and when the upper was removed (hand cycling the trigger).
Geissele said there are too many variables to warrant replacing it and that if it worked fine hand cycling then it should be okay. The engagement surfaces looked fine.
The weapon would occasionally burst while suppressed and continue going with the finger off the trigger then stop after a handful of rounds. The rate of fire was extremely high. Would love to see if there is a pattern here that would indicate how to repair it (heavier buffer?). Ultimately in this case the trigger was cheap enough that it was disposed to avoid further headaches.
Yep, same here. Like all the brass from a four round burst will land at approximately the same time. I'm estimating a good 900 rpm, which is the normal cyclic rate for an SBR.
I already tried using an H3 buffer and it didn't help.
And my understanding of bump fire is that the inertia of the bolt going home drives the gun into the trigger finger, so it seems like by definition the bolt would have to be in battery to cause the bump fire? In which case I shouldn't be getting hammer follow?
The rifle can bounce off your shoulder or a bipod as well. I believe it’s more likely with the recoil impulse of a suppressed rifle. Loading up the legs of a bipod while holding the rifle loosely works quite consistently.
The rifle can bounce off your shoulder or a bipod as well. I believe it’s more likely with the recoil impulse of a suppressed rifle. Loading up the legs of a bipod while holding the rifle loosely works quite consistently.
The silencer actually reduces the felt recoil by a lot. I think it's the faster bolt with the silencer that's exacerbating the issue, not the felt recoil.
This really is a strange issue. I know it's not unheard of, you're not the only one. But people, myself included, have 10s of thousands of rounds through their G triggers without issue. Wondering what happened with yours.
Which model trigger is it? I don't think you mentioned it.
The silencer actually reduces the felt recoil by a lot. I think it's the faster bolt with the silencer that's exacerbating the issue, not the felt recoil.
Something with the timing, or the reduced recoil makes the bolt closing recoil forward stronger.
Something with the timing, or the reduced recoil makes the bolt closing recoil forward stronger.
To get hammer follow though you have to have the hammer released before the bolt closes.
This really is a strange issue. I know it's not unheard of, you're not the only one. But people, myself included, have 10s of thousands of rounds through their G triggers without issue. Wondering what happened with yours.
Which model trigger is it? I don't think you mentioned it.
I think it almost has to have something to do with the 22 conversion kit. It worked perfectly before I started using it, and the issue seems to have kind of escalated with continued use. I would be curious to know if other people with this issue were using 22 conversions.
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