GMR15 Issues

[jk_nh]

I have a question that I hope the GMR15 experts out there can help me with.

 

I have a brand new GMR15 manufactured in October 2020.  It has the short stroke bolt and SCS and the competition hammer springs.

 

I’m having the same malfunction with every Glock mag and ammo type I have:  when I pull the trigger, there is just a click.  The round does not go off.  When I eject the round and check it, there is no firing pin dimple.  It is as if the firing pin did not make any contact with the primer.  For what it is worth, I am using Federal American Eagle ammo and Glock OEM magazines.  The GMR itself is clean and lubricated. 
 

For the JP experts, is this likely to be a problem with the firing pin spring being too light, or the hammer spring being too light?  The firing pin looked fine when I pulled it.  
 

This is my fifth JP Rifles PCC or AR; I’ve never seen this issue before.  
 

I’ve emailed JP already.  I’m hoping someone on the board has advice on a remedy.  
 

I’m grateful for any help.
 

 

[Sniperboy]

Did you modify the PCC in any way from the factory?

My guess is either:

 

1.  Your trigger is NOT resetting, in this case there would be no "click" of the hammer falling, but sometimes in the heat of the moment it can be hard to remember if the issue was a light strike or the trigger not resetting.  It has happened to me at matches, I had to sit down and try to recall if the trigger did reset or not.  Even if the trigger did not reset it should still have a very faint mark on the primer.  If the trigger did not reset, there will be no "click" and it will just be dead, with a live round in the chamber.

 

2.  Your firing pin may be broken, take your bolt apart and check. 

Edited July 25, 2021 by Sniperboy

[Nathanb]

The only time I’ve seen this with a silent capture system is caused by excess room in the rear of the buffer tube. It would allow everything to come into battery but not actually allow the bolt to have enough tension to allow firing pin contact.  
 

i fixed it with quarters in the buffer tube until the rearward play was eliminated and held the bolt where it should be. 

mine was a 5.56 gun but I’m sure it’s still the same concept 

[Sniperboy]

The idea of excess room is an interesting one.  I do not use an SCS so I can't speak from experience but if you changed your receiver extension/buffer tube or if your tube is a bit off maybe you need that horseshoe washer that JP provides with their SCS, or maybe it fell out when you cleaned it.  Just another option.

Here's the info.

 

 

[LowSpeedHighDrag]

How long are you loading the rounds? I had the issue with 380 ACP bullets loaded short, and the gun didn’t like it.

FWIW, I took apart my bolt once for cleaning and discovered the firing pin had broken.  Gun still worked.  Doesn’t mean it can’t break and stop the gun from firing.

 

[jk_nh]

Thank you for the ideas, guys.  To answer the follow-up questions:

- I have not modified the gun in any way except for adding optics;

- I did pull the firing pin that came original with the gun.  It looked fine; I have fewer than 300 rounds through the gun;

- I do not reload.  I have only used factory American Eagle 124gr ammo.

 

On the idea of adding quarters or the spacer in the buffer tube.  This GMR has the same pin on the buffer tube that comes with an AR to hold an non-SCS buffer in place.  Would that makes a difference in how much tension the SCS applies to the bolt?

 

I added one quarter in the buffer tube after the spacer but before the SCS.  Would I be better off using that spacer JP includes in the pack of O-rings?  Will one quarter apply the amount of tension I need?

 

Thank you again.

[AHI]

The gun worked 300 rounds. Then you did what?

Do you have a new firing pin to compare to the old one?

[AHI]

Reread your post. Can you lengthen the stroke a little. Comin issue to short and the trigger will not reset correctly.

[jk_nh]

AHI,

Do I lengthen the stroke by adding quarters or that shim from the package of O-rings?  Yes, I’ve put 300 rounds total through the gun. This problem has existed since Day 1. It is not a matter of shooting 300 then making a change. It is just the total mileage on the gun.  
 

Thank you for taking the time to answer.  I’m grateful for any input. 

[Kokeman]

When you close the top onto the lower is there pressure on the bolt from the captured spring? Can you hear or feel the spring rattle when all assembled? If you hear the spring rattle it just means the tube is a little long for your spring. Take the spring out and drop a quarter in the tube just to put a little preload on the spring. It will not affect the stroke.

 

[AHI]

Complete JP gun or build from JP parts.?

The ones I have been involved with . The scs has a bumper that was to long.

Involved grinding a little off the bumper stop to allow a little more stroke. and 

time for the trigger to set.

Edited July 26, 2021 by AHI

[Sniperboy]

The buffer retaining pin should not be an issue.  I have in the past tried the SCS with the standard non JP (small) pin and also with the pin completely removed and it works (granted it was not the short stroke SCS).

 

At this point, depending on how many PCC friends you have, you may need to try borrowing bolts and buffer systems then exchanging one by one to isolate the problem.  This solved many problems I had in the past though its quite tedioous.  WHo knows maybe your firing pin hole in your bolt got obstructed.

 

Also you need to figure out if your hammer is dropping and nothing is happening VS your trigger not resetting and having a dead trigger.  

[Tech32]

I believe that the JP bolt is designed so that the hammer won’t hit the firing pin until the bolt is all the way forward to prevent out of battery ignition. 
Is the bolt all the way closed when this happens?

[rowdyb]

On 8/2/2021 at 7:55 AM, Tech32 said:

I believe that the JP bolt is designed so that the hammer won’t hit the firing pin until the bolt is all the way forward to prevent out of battery ignition. 
Is the bolt all the way closed when this happens?

my guess is the ammo he is using is causing this.

[jk_nh]

Thank you very much for all your suggestions, guys. I emailed JP, asking if they have had any repots like mine concerning the GMR; they have not.

 

One of the tech support staff at JP called. I discussed with him the symptoms I outlined in my original post here.  He asked me to send the lower back to them. It was in the shop for a week.  I have it back already.

 

The statement of work they sent upon completion read that they reinstalled the fire control mechanism due to failure to reset and replace what they call EZ Disconnector.  
 

I am using at a local match tomorrow with factory Federal ammo, which is what I use normally.

 

I am grateful for all your input.  
 

thank you all again. 

[Th7]

So it was fire control and specifically the disconnector? 

[Ner]

it is always the same pack of problems

• disconnector little f*#ker spring (should be changed once a year) especially ECL

• firing pin + spring (should be changed once a year)

• too long/short stroke can cause a list of problems