New build 9mmAR pistol FTE issues

Hello all,

I have recently completed my very first AR build which is a 9mm pistol configuration.

The thought here is to eventually make this a SBR and put a silencer on it, but I don't want to start down that path until I know this pistol config runs 100% reliably.

Before I get into explaining my issues, here is a list of the parts I used to build this pistol.
- 5" ADCO barrel
- CMT slick side billet upper
- QC10 dedicated 9mm COLT style lower
- CMMG ramped 9mm bolt
- CMMG Lower parts kit
- ALG ACT trigger
- KNS trigger pins
- 9mm-Q buffer (8.5oz) + Wolf XP spring from heavy buffers .com
- Phase5 pistol buffer tube
- Various MetalForm magazines

Forgive me for the crappy pics from my phone's camera
Attachment 31179



I took it to the range yesterday for the first time and found I was having intermittent issues with failure to eject. Sometimes the ejected case would "stove pipe" and get caught between the closing bolt and the ejection port opening. But most times the bolt would be closed and appear to be ready to fire the next round, however the trigger was not reset. In those cases for example, I would fire the first round, stop to look at the ejection port and see the bolt appeared closed, start to release my trigger squeeze expecting it to hear it catch but find that the trigger wouldn't move forwards or backwards. I would not be able to put the selector on "safe" I assume because the trigger was not reset, but then when I would drop the mag and pull the charging handle back, I would see a case fall out the mag well. Not get ejected out mind you....but rather gently fall out the mag well or the ejection port if I had the pistol tilted towards that side.

I also have a factory 9mmAR rifle made by CMMG (which by the way has never given me any problems what so ever) so I switched out the bolt from that rifle and had the same issues. I then tried putting the buffer spring from the CMMG rifle into my pistol build and that seemed to help quite a bit. I thought I had fixed the issue but then unfortunately started having issues again...not as frequently...but still having the issue. This will sound crazy but it seems to be when the mag is freshly reloaded. I can put 20 rounds in the mag or 10 rounds and have the FTE on the first 1 or 2 rounds, and then it will fire the remainder of the rounds just fine. All of my mags do the same thing, so it isn't a particular mag. Also this happens with 115grn FMJ or 147 JHP ammo.

I may be way off here, as I am a real noobie, but my thinking is that there is an issue with the ejector in the QC10 lower.....or some sort of mismatch between the ejector and the bolt.

In the CMMG rifle the ejector is rock solid and has no movement. However in the QC10 lower the ejector moves quite a bit in any direction (up, down, left, or right). On the QC10 web page one of the selling points listed is a "self centering ejector" so I assume that is why the ejector moves around so much. I would love to put the pistol upper on my rifle lower to see if it behaves the same with the non-moving ejector in the CMMG lower, however that would be making a SBR and I don't want to go there even for testing purposes.

I did notice that on the CMMG lower that there is a pin for the ejector through the lower right below the bolt catch. However on the QC10 lower I can see right through the lower. There might be a pin there but it is not solid. Here is a pic where you can see day light right through the place where I would assume a solid pin would be. It looks like there is hollow pin perhaps...or is there no pin at all? Does anybody here have a QC10 lower that can tell me if they have a solid pin and/or if their ejector wobbles around?
Attachment 31181

Here is a pic of the ejector as I pull the bolt back.
It should be higher up shouldn't it? (if that makes sense)
Attachment 31183

I have read many threads so far about folks bending the ejector in towards the bolt to help with 9mmAR FTE issues. I can see that working on the CMMG ejector because it is solid and has no movement. But on this QC10 lower, the ejector moves around so I am not sure bending it would help if it can just move around anyway.

I am really hoping this is not a mag issue, as I live in Colorado and really want my already owned "15+ capacity" mags to work, since if I have to get new mags here they can not hold more than 15 rounds now....which means only 10 rnd mags :(

I know this is a lot to ask of you all, but if anybody can give me some pointers as to what to look for and what to try next , it would be greatly appreciated.
I don't want to submit a Form1 to make this a SBR until I have this thing running correctly.

Thanks !!

Quote:

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Originally Posted by bill4321

Hello all,
I did notice that on the CMMG lower that there is a pin for the ejector through the lower right below the bolt catch. However on the QC10 lower I can see right through the lower. There might be a pin there but it is not solid. Here is a pic where you can see day light right through the place where I would assume a solid pin would be. It looks like there is hollow pin perhaps...or is there no pin at all? Does anybody here have a QC10 lower that can tell me if they have a solid pin
I just bought a QC10 Glock lower, it is pinned, just not a solid one. It is secured (very well) with a heavy roll pin


and/or if their ejector wobbles around? Mine does as well


I have read many threads so far about folks bending the ejector in towards the bolt to help with 9mmAR FTE issues. Thats how my ejector is on my glock 26

But on this QC10 lower, the ejector moves around so I am not sure bending it would help if it can just move around anyway. Ya I think that would hurt more than help. My husband has a pistol (I can't for the life of me remember which one it is) that has a "self centering" ejector that wobbles a little side to side, and a TINY bit up and down.

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Hope this helps. I'm pretty green, but I'm learning fast!

FTE issue is solved !!

Just thought I would post here and advise that my FTE issue are resolved now.

I "googled" my issues but didn't find much help and that is why I posted here on this forum looking for input. However I was searching off of "QC10 ejector" and was not getting many returns. However once I searched for the former company DDLES, well then I found some tips and one of them turned out to be just what I needed.

Anyway.....here is what solved my FTE issues. The free-floating ejector built into the QC10 lower was rubbing on the channel in the CMMG bolt at area that is curved. I noticed there was a rub spot on both the ejector and also in the channel it rides in on the bolt. I used my Dremel to take out just a bit more metal on that curve in the channel in the bolt and now two things are better than before. First....The upper and lower go together much better now (used to be really tight and had to push hard to get the take down pin all the way in) and secondly my FTE issues are gone !

I went to the range tonight and ran 300+ rounds through this thing without one single issue. I tried 115grn FMJ, 147grn FMJ, and 147grn JHP and all ejected and fed perfectly.

I am a happy camper !
Next up....Form 1

Hope this info helps somebody else down the road.


Also I want to thank MPchinadoll for confirming that the ejector is supposed to move around....that really had me worried until I found out that it is supposed to do that :)

Quote:

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Also I want to thank MPchinadoll for confirming that the ejector is supposed to move around....that really had me worried until I found out that it is supposed to do that :)

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Glad I could help! And your resolution may help me a lot in case I have any issues once I get mine going. I wonder if the ejector will ride in the bolt the same since my bolt will have the glock mag relief cuts in the bottom?