9mm build fails to reset trigger

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[ARCHIVED THREAD] - 9mm build fails to reset trigger

Posted: 10/11/2018 9:47:47 AM EDT

Working on a friend’s AR9 build.

It will chamber, fire a round, extract, load the next round but will not fire due to the trigger not resetting.

Build details:
Colt PSA lower
Metalform mags
BA 11” barrel
Spinta Precision bolt
Kaw valley 7.5 oz buffer
Standard carbine buffer spring
Milspec trigger group

Solutions I’ve tried:
Reduced weight hammer spring
Reduced buffer weight (carbine, H, etc)
+p ammo

What’s going here? Is it the bolt?

ETA: jammer is bobbed and not notched
Cycling by hand with trigger held indicates it is hammer follow

Posted: 10/11/2018 9:53:05 AM EDT

[#1]

Try a new or stronger trigger spring and maybe a new disconnector.

Posted: 10/11/2018 10:01:57 AM EDT

[#2]

Quote History

Quoted:
Try a new or stronger trigger spring and maybe a new disconnector.

View Quote

@SScot

I will give that a shot.

Can you share why that might work? Trying to understand what’s going on here.

Posted: 10/11/2018 10:08:15 AM EDT

[#3]

Quote History

Quoted:

@SScot

I will give that a shot.

Can you share why that might work? Trying to understand what's going on here.

View Quote

From doing trigger jobs. I bend the trigger spring (and hammer spring and cut off the ear) to ease the pull (or use JP springs), if I go too far, it does not have enough pressure so I have to go back or install a new spring and then sometimes I have gotten bad disconnectors and have swapped those and it goes back. Most of the times when it happened to me you can manually move the trigger forward and it is stuck. Not saying this is what is happening to you but it is an issue I have ran into and figured it worth a try.

Posted: 10/11/2018 10:14:22 AM EDT

[#4]

Are you sure the hammer spring is installed correctly?

Posted: 10/11/2018 10:27:11 AM EDT

[#5]

Probably the disconnector spring.

Posted: 10/11/2018 10:29:27 AM EDT

[#6]

Have you confirmed you don't have hammer follow?

Posted: 10/11/2018 10:37:50 AM EDT

[#7]

Quote History

Quoted:
Are you sure the hammer spring is installed correctly?

View Quote

Verified but good thought

Posted: 10/11/2018 10:42:26 AM EDT

[#8]

Quote History

Quoted:
Have you confirmed you don't have hammer follow?

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I’m assuming that’s what is happening; the hammer is not captured for some reason.

Assuming components are new, what’s the fix?

Posted: 10/11/2018 11:32:49 AM EDT

[#9]

First check is (with firearm unloaded and pointed in a safe direction)

1) press and hold the trigger, hand cycle the bolt slowly, then release the trigger - does the trigger reset?

2) shotgun the upper open, press and hold the trigger. Manually cock the hammer and slowly release the trigger - does the hammer fall from the disconnector to the trigger or does it drop?

Posted: 10/11/2018 1:14:03 PM EDT

[#10]

Quote History

Quoted:
I’m assuming that’s what is happening; the hammer is not captured for some reason.

Assuming components are new, what’s the fix?

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
Have you confirmed you don't have hammer follow?

I’m assuming that’s what is happening; the hammer is not captured for some reason.

Assuming components are new, what’s the fix?

Take it apart, inspect and reassemble. Recheck. Replace if necessary.

Posted: 10/11/2018 1:48:18 PM EDT

[#11]

Prob forgot the disconnect...

Posted: 10/11/2018 3:19:08 PM EDT

[#12]

I’ve had a trigger which didn’t have the disconnector channel machined correctly/deep enough for the disconnector to rock back and forth hardly at all. Function tested fine manually pressing the hammer back but took an unusual amount of force to get it to catch while holding the trigger back. Might want to verify the slot is machined correctly. Just my 2 cents.

Posted: 10/11/2018 4:37:48 PM EDT

[#13]

Thanks guys.

Checked and the disconnector is present. Spring is correct. Going to reassemble with a fresh set of parts and see what’s up.

Posted: 10/11/2018 7:00:07 PM EDT

[#14]

Hyperfire 24C is what you seek

Posted: 10/11/2018 8:30:40 PM EDT

[#15]

Quote History

Quoted:
First check is (with firearm unloaded and pointed in a safe direction)

1) press and hold the trigger, hand cycle the bolt slowly, then release the trigger - does the trigger reset?

2) shotgun the upper open, press and hold the trigger. Manually cock the hammer and slowly release the trigger - does the hammer fall from the disconnector to the trigger or does it drop?

View Quote

@Circuits

1) the trigger does not reset

2) the trigger resets as normal

What now?

Posted: 10/11/2018 8:35:16 PM EDT

[#16]

Sounds like a plan.
Dano has posted over in AR-15 troubleshooting in the past about this. I know there are some differences mechanically between 9mm and 5.56, but I seem to remember that the hammer/disconnector tolerances being off kilter can cause this. Switching parts out may well work, but a deeper dive into the archives may help you find additional wisdom.
Please post back as to how it goes!

Posted: 10/12/2018 12:06:13 PM EDT

[#17]

Quote History

Quoted:

@Circuits

1) the trigger does not reset

2) the trigger resets as normal

What now?

View Quote

I'm guessing it's a ramped bolt (most are these days). In this case, it appears that the bolt's ramping doesn't push the hammer far enough down to catch on the disconnector, so it just rides home with the bolt as it goes back into battery.

The disconnector overlap will need to be adjusted, or the disconnector replaced so that the hammer is captured by the disconnector more reliably during the counter battery stroke.

Posted: 10/12/2018 5:39:50 PM EDT

[#18]

Problem solved.

Not sure what he did wrong but I removed the FCG and replaced it with another from my spare parts bin and...viola! It works.

Frustrating. Possible a tolerance stacking issue?

At any rate, dropped by his place, put a mag through it, he’s happy.

Thanks for the help!

Posted: 10/14/2018 1:42:40 AM EDT

[#19]

Glad it worked out. Post back if you can ever pin it down to more specific than tolerance stacking.
Best Regards,
rick

Posted: 10/14/2018 11:20:36 PM EDT

[#20]

Pretty sure your hammer and bolt didn't play well.

I assume the replacement hammer fixed things.

Posted: 10/14/2018 11:43:56 PM EDT

[#21]

Why in The F did it take this long to replace LPK group!?!?!? Toss bad shit start over .... no file this blend that!!! RR Lpk’s Are $40 bucks if you look.

I Shake My Head .... wow. I’m nobody but you All have thought it

H

Posted: 10/15/2018 2:22:49 AM EDT

[#22]

Quote History

Quoted:
no file this blend that!!! RR Lpk’s Are $40 bucks if you look.

I Shake My Head .... wow. I’m nobody but you All have thought it

View Quote

Show me ONE post in this thread where anybody said "file" or "blend" other than yourself. Stop projecting.

Posted: 10/21/2018 6:58:42 PM EDT

[#23]

I realized your problem is fixed but.....

The problem was most likely the hammer you was using. Was it notched or rounded?

I had the exact same problem and I found out that my rounded hammer was too rounded. I installed a less rounded hammer and it fixed my problem. And a notched hammer will not work at all either.

Posted: 10/21/2018 11:13:31 PM EDT

[#24]

Quote History

Quoted:

Show me ONE post in this thread where anybody said "file" or "blend" other than yourself. Stop projecting.

View Quote

Haha

Posted: 10/21/2018 11:13:44 PM EDT

[#25]

Quote History

Quoted:

Show me ONE post in this thread where anybody said "file" or "blend" other than yourself. Stop projecting.

View Quote

Haha

Posted: 10/22/2018 10:15:44 PM EDT

[#26]

[ARCHIVED THREAD] - 9mm build fails to reset trigger

AR-15 » Rimfire and Pistol Calibers

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