I am having an issue with my trigger not resetting when shooting suppressed. It is on a 10.5" AR with an M4-2000. I was having overgasing issues with an H2 buffer. The bolt was not locking back on the last round and it was jamming the next round half way into the chamber, so I went to an H3 buffer. I put about 100 rounds through it today unsuppressed, and had no issues with Wolf and XM193 with the H3. The bolt locks back on last round and no misfeeds. When suppressed every few rounds the trigger will not reset. The round is in the camber and bolt is fully closed. I built the gun using all parts from Noveske including the barrel. The gun has ~3000 rounds through it. Any ideas on what I can do to remedy this?
IMO If the bolt was not locking back and jamming the next round, it was short stroking. Try a H buffer. Maybe want to check the gas key to make sure that it didn’t get loose. But I am no expert.
So wait, it’s feeding the next round, but not resetting the trigger? If you manually cock it, does it then reset? Try doing a functions check over and over and see if you can get it to not reset.
I’ll put it this way, the bolt only needs to cycle about half as far to reset the trigger as it needs to feed a new round, so the problem isn’t it being over or under gassed. What sort of trigger mechanism are you working with? Standard semi auto?
Disconnector movement seems fine, but gritty. I took the trigger group out to inspect it. I noticed a shinny spot right above and just foreward of where the spring is. The tail of the hammer is hitting the disconnector. I am not sure if this is normal. My other AR has a Giesselle SSA-E and it is a different set up. I do have a spair CMT trigger group that I will try on my next outting. I compaired the two disconnectors, and the one in my gun was quite rough looking and was thicker. The one in the gun measured .123 and my spair was .118 and had a nicer finish.
Gas key is properly staked and tight. I had this problem with an H and an H2, that is why I went to the H3. It only happens when suppressed. No jams with the H3 though.
Yes. That is what I don’t understand. When I pull the charge handle it ejects the live round and will reset the trigger. It is a semi CMT trigger. I am leaning that it is a trigger issue too.
That’s normal wear. Which is to say it is wear. Next time it doesn’t reset pop your lower off and see if the hammer is actually locked back. I’d think it’d go full auto if the disconnect wasn’t catching the hammer anymore, but maybe not. And usually the weapon starts double-firing long before it goes full auto. It still doesn’t make sense that it’s only when its suppressed.
Doubling/Tripling/whatever may not happen if the hammer is riding the carrier forward. Running suppressed means you’re getting a lot more gas and maybe the extra speed of the BCG is causing problems. (similar to how and over-gassed gun’s BCG can outrun the mag follower or bolt catch).
The first thing I would try is a new disconnector and spring. After that, perhaps a sprinco blue or maybe even red buffer spring. Know anyone with the A5 setup?
A live round in the chamber with the hammer forward sounds alot like bolt bounce to me. If I read correctly you say it happens occasionally when suppressed and when unsuppressed it shoots fine. Since the suppressor increases back pressure this sounds like the problem.
If the tail of the hammer hits the disconnect, it can force the disconnect back onto its spring far enough to cause the disconnect not engage the hammer.
If the disconnect spring in turn is not fully up to tension/pressure rating or even a bit stiffer, and/or the disconnect is slow/gritty/binding in the trigger proper, the disconnect can remain disconnected long enough for the hammer to outrun its chance to get hooked.
Net result is the hammer rides the carrier forward and may or may not have enough ass depend on the speed it all occurs in X combination of parts to *slam fire or even just leave a small dimple on the cartridge primer.
*slam fire is really unlikely in general, or everyone would be pulling thier disconnect to get a slam fire full auto for about 30 seconds of work. It can happen of course, but its really quite rare and not something that can happen without a bunch of other magic circumstances at the same time. Or at least its never happened in the 50~60 times I’ve seen it deliberately tried or tried it myself over the years.
To get the hammer to hit the disconnect you’ve got to have some serious over gas/overpressure going on to blow the BCG back that hard to in turn shove the hammer back that stupid hard, which when taken into consideration that you said things work fine unsupressed but go to hell suppressed it sorta makes sense as putting on the suppressor will seriously ramp up gas pressures as I understand it.
I had a few (don’t remember the exact number) of BM carbines in Iraq that did the exact same thing. The gas ports were large to begin with and then over time got bigger (eroded). Once I replaced the barrels the problem stopped.
From what you have described it sounds like the exact same thing. Although I would be replacing cheap stuff first (springs, etc…) and would even see if I could find another lower (friend or other AR) that is known to work and then try it.
Could you explain how bolt bounce could cause this? You are correct that it only happens when suppressed.
I have never had a slam fire or have it double on me. I did check, and I still have 3 of the rounds that I ejected when it would not fire. All 3 had a very light dimple on the primer. My ejection pattern unsuppressed is back to about 4:00 and when suppressed it is straight out at 3:00
I am going to just try a whole new trigger group. Are the red and blue springs heaver? I do not know anyone with an A5. That was what I was going to go with, but the H3 was cheaper to try first.
If the problem is bolt bounce, I’m surprised that an H3 isn’t enough to counteract it. Where did you get the buffer? Do you know if it has the correct 3 tungsten weights?
Both my H2 and H3 buffers came from BCM. I just weighed them. The H2 is 4.60 oz and the H3 is 5.45 oz.
Thanks for all the advice everyone. I am going to try to get out next week and try my spare trigger, and maybe I’ll through in the SSA-E just to see what happens.
This thread went to hell in the proverbial hand basket after Markm’s post which was the only sound one in the thread. A good opportunity for a lesson in BASIC trouble shooting turned into SWAGfest.
A failure to disconnect can only involve the parts that live on the hammer and trigger pins. The order of inspection / replacement is disconnector spring, disconnector, hammer then trigger. Your wasting time and money investigating any other option.
As I said in my last post I will be trying a new trigger before I do anything else. I do appreciate all the input. It gives me and other people with similar issues other places to look if one does not work.