Suppressors Suppresed 9mm AR issue.

[2ndamendfan]

Well lets see what you guys know.
i have a 9mm AR that runs flawless. Finally got my SilencerCo hybrid out of jail. Took it out today and with the suppressor on, it would not cycle fully. It would load a round (9mm is short) but it wouldn't reset the hammer or lock back on an empty. Did it multiple times on 2 mags. Took the suppressor off and ran 8 mags about 180 rds and it worked perfect.
this is somewhat. Backwards of what i am used to on a gas gun. Normally the supressor adds back pressure and either needs less gas or a heavier buffer or both.
the 9mm is blow back, and just from experience it acts like it needs less buffer weight. I am running 8oz buffer, a 12 is recommended for suppressed from what i read.
Anyone have any experience or insight.

 

[smokin.338]

How is the suppressor locking up to the barrel, kind(s) of ammo use, and type of buffer (brand) ?

 

[2ndamendfan]

using ASR mount with ASR flash hider with 9 mm end cap. Most the ammo was 124 gr american eagle but I did try a mag of my defense ammo which is Barnes 115gr TAC-XPD +P 9mm. It did it 3 times in 20 rounds with that mag. Buffer is a heavy buffer's 8.5oz extended length 9mm buffer (broke 4 BHO before I got that).

 

[smokin.338]

Can you list a complete parts list of the rifle:
Barrel (length) -
BCG -
Trigger -
Lower type (style) -
Buffer spring type -

 

[A5scott]

I just built a suppressed (Griffin Rev9) Colt pattern 9mm AR (8.5")with the JP BCG, and it would cycle but not reset the trigger. It would extract and load a new round into battery, but not reset the trigger. The BCG ramp wasn't big enough to push the hammer down (Geissele S3G) thus the failure. I put an actual Colt BCG in it and it was fixed. A call to JP cs confirmed that their BCG doesn't work with all triggers. Chances are it's your BCG/hammer combo, but like you said, it's not exactly making sense, that when you remove the can, it cycles. I also used 4 different buffer weights, and it ran better, but harsher with a lighter buffer, but switching to the Colt BCG and back to the standard 9mm buffer fixed it.
shouldn't be too much trouble to get it sorted out.

edit... my build had the same type of failure suppressed and unsuppressed until the Colt BCG.

Scott

 

[2ndamendfan]

A5scott I do appreciate the response. would yours lock back on an empty mag? Mine would not, leaving me to believe that it is not making a full cycle. if it would lock back but not reset the trigger then I would definitely look at the trigger. Hell I will go look at the trigger now in fact, you never know.

 

[A5scott]

yes mine would lock back on an empty mag, especially with the lighter buffers I tried. Will yours will lock back on an empty mag by pulling the charging handle? Maybe put a little grease on the hammer and run the bolt, see if it contacts the BCG ramp. What BCG and trigger are you using?

Scott

 

[2ndamendfan]

It runs flawless without the suppressor. Locks back and hammer resets. It will lock back with charging handle also. Running BCG. That came with the gun. Gun was originally a pistol that i registered as SBR on a form 1. Trigger is a Timney. Gun has about 1800 flawless rounds rhrough it until the addition of suppressor this weekend. Trigger has been in it for about 500 rounds without issue. 8.5 oz buffer has been in for about 700 rounds.

 

[A5scott]

Yeah, that is a brain teaser.

Scott

 

[FunkyTownScout]

Could it be outrunning the the gun due to being overgassed? Not sure if it's possible.

 

[Strykervet]

You COULD have done damage to the trigger group or the pins or the holes in the receiver, considering you went through a few bolt catches already. In short, the damage could be done and you should start by checking that. Do the pins still fit snug, no wobble when you test 'em out? Same with the trigger and hammer? Is there excessive wear on the hammer face, say from the BCG? You said you built it yourself, and since there is no milspec that I'm aware of, so are you sure that you have parts that all do in fact work together? Ie, are all parts compatible?

Now you've changed the weight of the system and alleviated the excessive recoil. But you've also added a suppressor, so now you have a new problem --not enough recoil.

It seems these weapons are finicky, I went with .300BLK before I got a 9mm AR. Did my research, took my time, and along came .300BLK; I bought a 16" AAC upper and never looked back, and now I have 'em in 8.2, 8.5 and 10.5" also. They all use different cans all cycle flawlessly with supers or subs, with or without the can. Amazing.

Anyway, you may have to try different weight and spring combinations and may have to settle on a particular load or family of loads, say 124+P or +P+ (if they can handle those) or 147gr. for better suppression. May be able to get away with +P's for extra power. And the longer barrel will help a lot, regardless of the round chosen. My $.02.

But always start by calling the mfg. and see what they say, that's who I call first. If I can't get ahold of them or a satisfactory answer (rare) then I come on here and ask to see how (x item) has worked out for you guys.

 

[anarchist]

5.5 oz buffer is what the 9mm AR was designed for. I'd start there. I used a JP Silent Capture Spring on my build and it ran flawlessly from the first round with or without the can on it. It's got a 5" TROS 3-lug barrel, RRA bolt with the weight removed, JP SCS, SiCo Octane 45K with 3 lug mount, Geissele SSA trigger, QC 10 Colt lower.