WTF happened here? Pew go boom?

[ma96782]

I haven't seen 9mm trigger groups. Any idea what is different on them?

AR-15 Hammer Comparison and FAQ

Aloha, Mark

 

[Hueco]

They are not designed for use in PCC. Please see the message below for geissele and you have voided the warranty.

Please note, our triggers are designed for mil-spec AR15/M4 carbine rifles. Our AR15 triggers are not compatible with the Sig MPX/MCX weapons or Pistol Caliber Carbine AR15/M4 variants. Using them in these platforms will void the warranty. Please refer to our Super MCX SSA or Super MPX SSA if you are using these platforms.

I will purchase said trigger from you for $50 so you can buy a trigger built for PCC which is a blow back gun not a gas gun like the AR15 platforms. The problem is 99.9% likely to be the S3G Trigger.

I feel blessed by your generous offer this Christmas season. But, I'd feel just so terrible if I sold a defective product to another member.

I think instead, I'll move this trigger to the 14.5" 3-gun build, move the Larue MBT currently in that to the parts bin…and well, I just can't leave a trigger group homeless for the winter. I'll just have to build another lower. Win win win.

 

[wupddu]

My 9mm AR did take some break-in and tuning. They are not the same as a gas gun. I think the recoil has to be tuned. Lot's of info out there on it.
Put a std. AR or 9mm trigger in it and work from there.

 

[titsonritz]

https://centurionarms.com/parts-accessories/triggers/new-enhanced-pcc-hammer/

 

[osprey]

I have built a couple 9mm ar's both using alg act triggers with nary an issue. One was a joe bob's matched set with lrbho and dedicated glock mag lower. The other was aero precision upper with a regular ar 15 lower using endomag conversion. I assume you are using a longer/heavier buffer made for the blowback pistol rounds?

 

[rdb241]

The 9mm bolt is not locking............

9mm bolts do not lock. They are a solid head bolt and is part of the carrier. I have 2 9mm carbines and both are the same way. No bolt head to twist and lock into anything.

 

[dmmv]

I've got a CMC 9mm trigger sitting here, you're welcome to run for a while. It's the only part I've picked up for my PCC build and I'm not going to start buying other parts any time soon

 

[Hueco]

9mm bolts do not lock. They are a solid head bolt and is part of the carrier. I have 2 9mm carbines and both are the same way. No bolt head to twist and lock into anything.

*most don't. CMMG's radial delayed bolt locks. If it weren't so damn expensive, I'd prefer that one over the direct blowback bolts.

 

[Member 34319]

*most don't. CMMG's radial delayed bolt locks. If it weren't so damn expensive, I'd prefer that one over the direct blowback bolts.

They have their own set of quirks and issues though.

 

[Defense Minister]

Could the timing be off for some reason such that the bolt begins its journey rearward before the bullet has left the case thereby exposing the case to rupture?

 

[RyanG90]

There's a guy looking to buy one of these in another thread. We should connect you two.

What trigger?

Never mind, it's in the first post. I blame the trigger. Replace that with something 9mm rated or a really basic stock trigger.

I'm running the Rise armament 3.5lb drop in trigger in my EPC9.. never had a single issue.

 

[po18guy]

All I know is I had a case head let go in my first HK91. Def the case. I can say that I've been hit by ten .308 rounds and lived. Unfired rounds that is.

 

[Member 34319]

I'm running the Rise armament 3.5lb drop in trigger in my EPC9.. never had a single issue.

It's not an exact science. I've run a good amount a of various triggers in 9mm blowbacks, occasionally one just doesn't want to be abused in a blowback 9mm and causes grief.

 

[rdb241]

All I know is I had a case head let go in my first HK91. Def the case. I can say that I've been hit by ten .308 rounds and lived. Unfired rounds that is.

View attachment 1089668

View attachment 1089669
View attachment 1089670

So what do you think was the cause of this? I have had this happen with an AR-15 and I know why. Just wondering if it is the same reason. Not only did it destroy the mage but it also distorted both the upper and lower receivers. I am very familular with HKn 90 series firearms. So I am very curious what you think caused this.

 

[po18guy]

So what do you think was the cause of this? I have had this happen with an AR-15 and I know why. Just wondering if it is the same reason. Not only did it destroy the mage but it also distorted both the upper and lower receivers. I am very familular with HKn 90 series firearms. So I am very curious what you think caused this.

Milsurp. Some with Nato headstamp and some Greek.

 

[Mike_M57]

So what do you think was the cause of this? I have had this happen with an AR-15 and I know why. Just wondering if it is the same reason. Not only did it destroy the mage but it also distorted both the upper and lower receivers. I am very familular with HKn 90 series firearms. So I am very curious what you think caused this.

My first thought was secondary detonation from an under-loaded cartridge. Wild Azz Guess, probably wrong.

 

[rdb241]

My first thought was secondary detonation from an under-loaded cartridge. Wild Azz Guess, probably wrong.

I would agree. When my brass separated, it stacked another round behind what was still in the chamber and the round went off with no where to go.

 

[Mike_M57]

I would agree. When my brass separated, it stacked another round behind what was still in the chamber and the round went off with no where to go.

I was referring to the OP's kaboom and something called Secondary Detonation, or Underload Detonation, or Secondary Explosion Event (that's a new one on me). Underloaded cartridge makes powder detonate instead of burn rapidly. They warn about it in reloading manuals. I know the OP said the ammo used was commercial, but stuff happens. I thought it might be ammo related, but apparently it was the trigger.

Like I said, I'm WildAzzGuessing.

 

[Hueco]

The saga continues ladies and gents!

Since my first post, I've experienced so much unintentional automatic fire, I think ATF man may be following me.

I've tried different triggers, springs, buffers...all to no avail. To recap, this is an Aero EPC-9 lower and upper, standard carbine buffer tube, 8" barrel.

Here's what's been run:

• Original test
  • Geissele 3-gun Trigger
  • Sprinco Red buffer spring
  • Spikes extra length (giggity) 7.7oz buffer
  • Result: Unintentional Auto / Out of battery Ka-Boom
• Test 2: The OEM Test
  • Timney AR-9/PCC Trigger
  • Aero 9mm buffer spring (I believe they use a .308 spring)
  • Aero Extended Buffer 7.7oz
  • Result: Unintentional Auto
• Test 3: Losing Weight
  • Rise Armament RA-535 (PCC rated trigger)
  • Angstadt Arms PCC Buffer Kit (Standard Carbine spring + spacer)
  • 5.4oz Buffer
  • Result: Unintentional Auto
• Test 4: Going Anorexic
  • Rise Armament RA-535 (PCC rated trigger)
  • Angstadt Arms PCC Buffer Kit (Standard Carbine spring + spacer)
  • Tested with Spikes T1, T2, and T3 spacers (3oz, 4oz, 5.5oz respectively)
  • Result: Unintentional Auto

So, as you can see, I've tested 2 different PCC rated triggers with a variety of buffer assemblies going from decently heavy (Sprinco Red + 7.7oz) to stupid lightweight (Standard Carbine + 3oz). Every time - unintentional automatic fire.

When the gun does stop shooting, the trigger is not reset. So I'll yank the bolt back and inspect the last chambered round - it will always have a light strike. So...yep...trigger not resetting.

The only thing that I have NOT tried is a different BCG. I just got a replacement for the Aero BCG from FailZero and am excited to give it a burn. Note the differences in the builds:



Aero on the left, FZ on the right. I wonder why Aero chose not to support the bottom of the case while FZ did?



Aero on top, FZ on bottom. Taking some quick measurements, the FZ channel/ridge that will be in contact with the hammer on reset is roughly .002~.003" taller in length than the same spot on the Aero. At this point, well I'm still guessing of course, but I think my Aero BCG may be out of spec, leading to it riding over the top of the hammer reset point.

But, I guess we'll see.

Thank you to everyone who has contributed to this thread so far and thank you to anyone who jumps in with other thoughts, ideas, experience.

Cheers,

 

[3MTA3]

The saga continues ladies and gents!

Since my first post, I've experienced so much unintentional automatic fire, I think ATF man may be following me.

I've tried different triggers, springs, buffers...all to no avail. To recap, this is an Aero EPC-9 lower and upper, standard carbine buffer tube, 8" barrel.

Here's what's been run:

• Original test
  • Geissele 3-gun Trigger
  • Sprinco Red buffer spring
  • Spikes extra length (giggity) 7.7oz buffer
  • Result: Unintentional Auto / Out of battery Ka-Boom
• Test 2: The OEM Test
  • Timney AR-9/PCC Trigger
  • Aero 9mm buffer spring (I believe they use a .308 spring)
  • Aero Extended Buffer 7.7oz
  • Result: Unintentional Auto
• Test 3: Losing Weight
  • Rise Armament RA-535 (PCC rated trigger)
  • Angstadt Arms PCC Buffer Kit (Standard Carbine spring + spacer)
  • 5.4oz Buffer
  • Result: Unintentional Auto
• Test 4: Going Anorexic
  • Rise Armament RA-535 (PCC rated trigger)
  • Angstadt Arms PCC Buffer Kit (Standard Carbine spring + spacer)
  • Tested with Spikes T1, T2, and T3 spacers (3oz, 4oz, 5.5oz respectively)
  • Result: Unintentional Auto

So, as you can see, I've tested 2 different PCC rated triggers with a variety of buffer assemblies going from decently heavy (Sprinco Red + 7.7oz) to stupid lightweight (Standard Carbine + 3oz). Every time - unintentional automatic fire.

When the gun does stop shooting, the trigger is not reset. So I'll yank the bolt back and inspect the last chambered round - it will always have a light strike. So...yep...trigger not resetting.

The only thing that I have NOT tried is a different BCG. I just got a replacement for the Aero BCG from FailZero and am excited to give it a burn. Not the differences in the builds:

View attachment 1128311

Aero on the left, FZ on the right. I wonder why Aero chose not to support the bottom of the case while FZ did?

View attachment 1128312

Aero on top, FZ on bottom. Taking some quick measurements, the FZ channel/ridge that will be in contact with the hammer on reset is roughly .002~.003" taller in length than the same spot on the Aero. At this point, well I'm still guessing of course, but I think my Aero BCG may be out of spec, leading to it riding over the top of the hammer reset point.

But, I guess we'll see.

Thank you to everyone who has contributed to this thread so far and thank you to anyone who jumps in with other thoughts, ideas, experience.

Cheers,

Agree, the carrier is definitely the next step. I was also just thinking that if the firing pin could somehow get stuck would it not slam fire making it go auto until it returned to normal? Perhaps that could explain the light primer strike on the last round?