CMMG problem (update with pic in post #5)

newshot

newshot

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Hi,

I am new to ars, haven't even shot one in .223 yet. I took my CMMG stainless conversion to the range and it fired the first mag no problem. Cycled the ammo perfectly and went through about 20 rounds. Then I load the next one and it clicks but doesn't fire. So I eject the round (ejects perfectly) no mark from the firing pin. I do it again and the same thing. Then I go to open the AR to look inside and it won't open (just the rear pin at this point) So I pop the front pin and then the second and the gun opens up. The buffer and spring have come forward and knocked the kit too far forward (maybe 3-4 millimeters so it is no longer flush with the upper) causing the hammer not to make contact maybe? Anyhow, I put it all back together (takes a bit of forced to pull the .22 kit out) and the first round fires, but then click click, same thing has occurred. The pin that sticks up in front of the stock and holds back the buffer seems fine and I have a new spikes tactical buffer in there. Any idea why the spring and buffer are coming forward? Any part in particular sound like it needs attention/replacing? I do not think it is a problem with the .22 kit, I think it is an issue with the lower.

Any input would be great thanks :)
 
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the buffer is retained in place in the tube by a plug with a point on it. You will see this in front of the buffer, bottom of the receiver. The buffer tube is threaded into place just far enough to cover a portion of this plug so it doesn't pop out, but not so far that the plug can't stop the buffer from coming out under normal operation. I would start by looking here.

The plug was the best thing they could come up with to hold the buffer in the tube, but still allow us to remove it for cleaning.

Good luck,
Jeff
 
My thought was it has to be that plug, but it looked fine. Is it possible the spring underneath it has weakened and needs replacement?
 
conversion troubles

If the tube was installed incorrectly it can be to far forward an already pushing the detent down allowing spring/buffer to "crawl" forward to far.It should be installed so that approx 2/3 of lower step on detent is covered as close as possible to maintain correct indexing for carbine style tube.To far forward may cause a short stroke with a .223,sometimes these kits also require some tuning.If tube was not deep enough(to shallow) it can cause a slight tilt in detent operation(sticky,canted in channel). In the extreme if not far enough in detent will not stay in place at all.
 
OK, so I believe the buffer is unconnected to this issue. I install the cmmg flush with the receiver and it works for one shot, sometimes two. Then click, click, click. While this is occuring the rounds are feeding perfectly, but there is no contact on them from the firing pin. Everytime I pull the charging handle a full untouched round cycles out perfectly. Then when I open the upper the kit is no longer flush with the receiver and the buffer has come out.

The buffer issue is just a result of the bigger issue which seems to be that the kit is sliding too far forward in the upper (I think it is pushing the plug down when closed, then because it inches forward the buffer slides out). I was able to duplicate the problem by simply pulling the charging handle a few times without connecting the upper to the lower and I could visually see the kit moving forward, so it is not being caused by anything to do with the lower. I also did it with the gun assembled but the buffer removed and again duplicated the problem.

Below is a pic of the kit in the "too far forward and won't fire" position.


This is how it look when it won't fire:

problem-600x450.jpg


This is how it looks when it will fire:

working-600x450.jpg


Here are some detail shots of the kit:

24-600x450.jpg


33-600x450.jpg


43-600x450.jpg


Any ideas?
 
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newshot said:
OK, so I believe the buffer is unconnected to this issue. I install the cmmg flush with the receiver and it works for one shot, sometimes two. Then click, click, click. While this is occuring the rounds are feeding perfectly, but there is no contact on them from the firing pin. Everytime I pull the charging handle a full untouched round cycles out perfectly. Then when I open the upper the kit is no longer flush with the receiver and the buffer has come out.

The buffer issue is just a result of the bigger issue which seems to be that the kit is sliding too far forward in the upper (I think it is pushing the plug down when closed, then because it inches forward the buffer slides out). I was able to duplicate the problem by simply pulling the charging handle a few times without connecting the upper to the lower and I could visually see the kit moving forward, so it is not being caused by anything to do with the lower. I also did it with the gun assembled but the buffer removed and again duplicated the problem.

Below is a pic of the kit in the "too far forward and won't fire" position.

problem-600x450.jpg


Any ideas?
Click to expand...

A better camera? :D
 
can you also take detailed pics of the .22 conversion itself? i have a similar kit and can't see how this is occurring unless there is something wrong with the chamber end.
 
Clubhopper said:
can you also take detailed pics of the .22 conversion itself? i have a similar kit and can't see how this is occurring unless there is something wrong with the chamber end.
Click to expand...

I will take pics of the kit.


The ammo I am using is fed bulk packs, the 525s. But this occurs with or without ammo if I just pull the charging handle a couple times.
 
Armourall said:
A better camera? :D
Click to expand...

har har :p

I posted some detail pics of the kit as requested and also an image of how the kit lines up when it does fire (all pics added to post #5). Another give away that it is going too far forward is that the dustcover won't close.
 
1) Did you ever take apart the conversion?

2) Have you contacted CMMG yet? Via. Email or Phone. They're guys are awesome at taking care of customers.
 
conversion looks fine to me.

what kind of upper is your AR-15?

from what i can tell the kit looks fine near the chamber end. i just took a look at mine and there is no possible way for the kit to move forward like that unless the upper was out of spec somehow.

see the rails that the .22 bolt rides on near the chamber area? the rail ends press up against the upper's chamber and limit that sort of movement you are experiencing.
 
I have a second hand CMMG kit (which I bought in the EE). I had the exact same issue with my kit. It was very frustrating I shelved the kit for review at a later date.

I have an LMT which works perrfectly w/o the conversion kit. When the kit is in, I get the first two, maybe three rounds off...then FTF without a firing pin mark on the .22 rim.

I have to see if my kit does the same thing in terms of movement.

Any assistance would be very much appreciated.
 
Again, I'd highly recommend talking to CMMG.

If it's an issue with the kit (there were a certain number with issues) I'm sure they'll replace it for you.
 
It is an armalight m15 upper.

I sent an email to CMMG. I will post if I get a fix or replacement for this. Thanks! Any other ideas in the mean time are welcome.
 
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