CMMG 22LR Upper not going to battery

Bertfish · Aug 1, 2014

Bought a CMMG .22 LR upper receiver for an AR a few months back. Read a lot of good reviews and thought that it'd be fun for me and the girlfriend.

It is having a constant issue with failing to go completely to battery. Always seems to happen on the second to last or last shot in the magazine (I have one CMMG magazine that came with the upper). The bolt will only be out of battery by about 1/16th of an inch which obviously prevents it from firing.

I did some googling and found that some folks CMMG uppers hang up on their bolt catch which would take some inertia away from the bolt and could cause this issue. I dressed the top of the bolt catch up a bit with a file but it hasn't helped.

Any suggestions on what else I could try? It's awful suspicious that it only seems to happen when the magazine is nearly empty.

Augie · Aug 1, 2014

For what it's worth I usually try other mags before messing with the firearm.

clandestine · Aug 1, 2014

Are you sure the carrier (the part that stays still) isn't bumping? There's a plug that gets stuck in front of the factory buffer that tensions the .22 carrier and keeps it from moving.

I think its called a tac plug. They do help guns that are inconsistent.

rdc · Aug 1, 2014

I had the same issue and it was the bolt hold open adapter. If you take it out does it still happen? I had to take A LOT of material off my BHO adapter to get it to work properly. I can post a pic of how I had to take off later tonight.

my69rox · Aug 1, 2014

send Justin an email at CMMG , he has help and gave me free things to fix my kit . Mine works great now. "JustinH" <justinh@cmmginc.com>

Bertfish · Aug 1, 2014

clandestine said:
Are you sure the carrier (the part that stays still) isn't bumping? There's a plug that gets stuck in front of the factory buffer that tensions the .22 carrier and keeps it from moving.

I think its called a tac plug. They do help guns that are inconsistent.

Is there a way I could tell that this is happening?

rdc said:
I had the same issue and it was the bolt hold open adapter. If you take it out does it still happen? I had to take A LOT of material off my BHO adapter to get it to work properly. I can post a pic of how I had to take off later tonight.

If I remove the magazine it doesn't seem to happen. Only seems to occur on the last or next to last round in the magazine which is why I am inclined to blame it on the mag. Pics of what you did would still be appreciated

my69rox said:
send Justin an email at CMMG , he has help and gave me free things to fix my kit . Mine works great now. "JustinH" <justinh@cmmginc.com>

I think I will do that, thanks!

Nanook · Aug 1, 2014

Silly question: you are using good lube, right?

rdc · Aug 1, 2014

I just re-read your post. Are you using the optional bolt hold open adapter? That's what gave me issues. If your not using that I'm not sure what the issue is. Which mags are yo using?

rob-cubed · Aug 1, 2014

Yeah I don't have the version with a bolt catch and have not had any problems, with any mags.

Is it easy to remove the bolt catch? I'd try shooting with it that way first.

And, CMMG has been very helpful in the past. Highly recommend calling them, they really stand by their products.

clandestine · Aug 1, 2014

Is your hammer notched?

photoracer · Aug 1, 2014

I have a CMMG conversion kit that I later made into a complete upper using a Taccom alloy sleeved barrel. I did not have any problems initially using the CMMG gray mags. Now I tend to use the steel-lipped BDM mags and have no issues. I have both a bolt hold open adapter and the adapter to use S&W 15-22 mags. I tried both and did not find them 100% reliable and as yet have not done any rework on them either (I also own 2 15-22s).

Jeip24 · Aug 1, 2014

Check out the Taccom reliability kit. It is the best thing I have bought for my dedicated .22 upper. It comes with the plug clandestine is talking about. It's well worth the money. Mine will eat just about anything.

http://www.taccom3g.com/22RF_RELIABILITY_KIT.html

Bertfish · Aug 2, 2014

rdc said:
I just re-read your post. Are you using the optional bolt hold open adapter? That's what gave me issues. If your not using that I'm not sure what the issue is. Which mags are yo using?

The bolt does hold open so I assume that the upper came with the adapter

Bertfish · Aug 2, 2014

clandestine said:
Is your hammer notched?

Not sure, it is a stock AR hammer from a PSA parts kit. I will check later

I am no expert on the AR platform so I often don't know these things off the top of my head

photoracer · Aug 2, 2014

Bertfish said:
The bolt does hold open so I assume that the upper came with the adapter

Maybe and maybe not. All the .22 conversions mags have a tall follower that stops the bolt when the mag is empty. If when you pull the mag out the bolt closes you do NOT have the bolt hold open adapter.

rdc · Aug 2, 2014

Bolt hold open adapter. Do you have this?

rdc · Aug 2, 2014

I did this a year or two ago so I don't remember exactly how much I took off but I know it was a lot. I had to take off material from pretty much every face to get full functionality with all my mags (sebpveral types).Basically when a mag was installed the tab was being pushed up into the bolt and preventing it from going fully into battery.
Give CMMG a call they were really helpful when I had a different issue. I probably should have called them about this part but I was bored and determined to get it to work.
I'm using a standard no frills PSA LPK.

Bertfish · Aug 2, 2014

rdc said:
Bolt hold open adapter. Do you have this?

No, I do not. 100% sure that is not there

rdc · Aug 2, 2014

Don't know then. Sorry. Thats what caused all my out of battery problems. FWIW I think I'm going to order the plug and other parts that were recommended above.
Mine still isn't as reliable as I'd like.

erwos · Aug 2, 2014

I had issues with a Spike's gun because my normal BHO was rubbing up against the bolt. I had to grind it down SUBSTANTIALLY to fix the problem. If you can safely remove it (ie, you have the right punches), consider popping the BHO off entirely to see if that resolves anything.

I'd contact CMMG otherwise.

CMMG 22LR Upper not going to battery

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