Without the suppressor it runs fine. With the suppressor I get light primer strikes…or maybe bolt not going fully into battery. The AR pistol was very dirty. I attempted to do a quick cleaning on the range that maybe helped a bit but ultimately went back to failing every few rounds. I wouldn’t say it was jamming either. It appeared like rounds were fully chambering and when trigger was pulled, “click” no discharge. I’d drop mag and eject live round. The rounds look have a very light primer strike. I can post pics of the rounds and my wife might have taken a video. I will find out later and post it up if so.
I did swap BCAs with another rifle at one point and the same BCA ran fine in a 16” AR15 rifle but the issue continued on the AR Pistol w/ suppressor. It seemed like the issue got progressively worse as the day went on.

I assume this is a gas issue? Or maybe fouling building up?

Any ideas? I’m new to suppressors and troubleshooting gas issues. Thanks dudes.

AR15 pistol in question. 5.56 NATO. Aero Lahar 30K can, 8” Ballistic Advantage bbl, M16 BCA. Shooting Winchester M193 and some green tip.
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Trigger is a Larue MBT. Yeah the SB HBPDW brace replaces the buffer tube/spring/buffer. It all works fine without the suppressor. Should I try putting a standard trigger group back in?

I appreciate any ideas info.

Sounds like a trigger/FCG issue.  Are you sure you’re getting an actual “click” when you pull the trigger?

I only ask because you’ll have a small dimple on the primer every time you chamber a round in an AR due to the free floating firing pin.  Are your primers just slightly dimpled?  Or are you getting legit light primer strikes?

My immediate thought would be you’re so overgassed when suppressed the bolt carrier is outrunning your disconnector’s ability to catch the hammer when the BCG cycles.  If you’re actually getting a full trigger reset and the hammer is actually falling on the subsequent trigger pull, that can’t be the issue though.

If it were my gun, I’d swap the FCG to isolate those parts.

ETA:  That’s a 5.56 gun?  Theres a good chance you’re extremely overgassed if there’s not an adjustable gas block on there.  You’re even worse off with that brace/recoil system choice.  Shorter than typical pistol gas 5.56 barrels typically have massively hogged out gas ports because manufacturers need them to function unsuppressed.  This can cause a lot of issues when you introduce a suppressor that isn’t designed for low backpressure (the Lahar-30 isn’t).

Maybe try installing the heavy spring that comes with the larue trigger.
That would be a good place to start.

I got light primer strikes because my gun was so filthy the firing pin was seized in place (had to pry it out) or the trigger assembly was so nasty.  I must have put 1000 plus rounds without cleaning and then let it sit for months.  It fired the first round then failed on every single other I tried.  I guess it could have been something else but it took a lot of effort to get that firing pin out.  Threw everything in an ultra sonic cleaner and it worked perfectly.

You sure it’s legit light primer strikes? Pics of rounds?

Here is a pic of the rounds.

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Those are dimples from the round chambering.

The trigger was definitely resetting. We were getting a very noticeable “click” when the trigger was pressed. Hammer would drop, we would have to recharge the pistol to try firing again. These were some of the rounds being ejected.

Yup. OP what buffer setup is in there? With an 8” 5.56 barrel (and that’s a whole nother can of worms), and presumably a pistol length gas system, you’re probably very much overgassed with the can.

Sounds like the gun wasn’t fully in battery then.  Do you have another lower you could swap on there with a standard buffer setup?  I have one of those HBPDW/Q setups and the buffer is fairly light.

This is what I am thinking also now. Just got off the phone with my friend. He said he was able to charge the pistol and hit the forward assist and it would put the carrier into battery and it would fire every time.
I do have another lower I can swap in but I won’t be able to fire it until sometime this week.

If that is the case, what are my options to remedy this?

Check the FCG and make sure there is not any debris present that could slow the hammer fall. I've seen back pressure from a suppressor drive crud, debris, and blown primers into some improbable places. Similarly, check the firing pin channel on the bolt. Again, back pressure can force crud into very creative places.

SilentMike
Dead Air
AAC 1998-2018

If you’re wanting to keep that style brace/buffer, likely an AGB.

Likely this.

Thanks guys. Any recommendations for the lowest profile adj gas block that will fit under my SLR rail? There isn’t much room under there.
I will probably cross post this question in the AR Discussions section also.

Also. Does this look like an excessive amount of gas leaking out from under the gas block? I noticed the inside of the rail is gray with gas residue also. Seems like a lot to me. Not sure if the pic will show it as well. I feel like the whole damn thing is coated/dusted.


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SLR sells adjustable gas blocks that will fit under your SLR rails.

Good call. Thank you! I’ll get one ordered.

Double check to make sure the spring wasn't installed incorrectly. I have the MBT on all my ARs (suppressed) and have never had a light strike.