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CMMG conversion kit failures and auto bursts

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I've had a stainless CMMG .22 conversion kit for years now and never really had any issues with it until recently. I noticed the bolt was having a hard time going into battery on all 4 of my ARs. Even after shooting, trying to get the bolt out required me to use a hammer and punch so I knew something was up as it was getting really stuck in the upper. I emailed CMMG support and they sent me a new chamber insert/collar because they think the one I had swelled up and was the reason for it being so tight. The new collar arrived and was easily seated into battery and easy to remove in all my rifles.

Today I went to the range to test the new part and noticed on the first magazine, using (3)black dog 10rd mags w/stainless feed lips and Federal automatch .22lr ammo, that the gun would not cycle properly. I was getting failures to feed, extract, stovepipes, and 2-3rd bursts. I pulled the bolt out, broke it down, inspected it etc...all looked good. Put it back in the gun, and same issue for all 100rds I shot through the rifle. Rifle is a Bushmaster M4 E2S carbine and this same bolt, sans the new collar, has been shot many times without issue. I have also shot many rounds of .223/5.56 with no issue.

I plan to email CMMG support again to see what they say, but what could be the problem here?
 

mac1911

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I had a older cmmg kit. It never ran 100%
I had the upgrade locking lug bushing.
What I found with mine was the extractor would get beat up quickly...I actually went through 3 of them.
The grove and pin also get filled with crud quickly also. Be sure the F pin is moving freely.
Fouling finds it way into the deepest crevices of the unit.
Your doubling could just be a fire pin that's not moving freely.
 
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I had a older cmmg kit. It never ran 100%
I had the upgrade locking lug bushing.
What I found with mine was the extractor would get beat up quickly...I actually went through 3 of them.
The grove and pin also get filled with crud quickly also. Be sure the F pin is moving freely.
Fouling finds it way into the deepest crevices of the unit.
Your doubling could just be a fire pin that's not moving freely.

Firing pin seems to move just fine and is not fouled, nor is the channel it resides in. The kit was completely clean before using today.
 
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apparently there is a firing pin spring that is supposed to slide over the firing pin. I am missing this part and honestly, don't ever recall seeing it there. CMMG is sending me two in the mail. Hopefully this fixes the issue.
 
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apparently there is a firing pin spring that is supposed to slide over the firing pin. I am missing this part and honestly, don't ever recall seeing it there. CMMG is sending me two in the mail. Hopefully this fixes the issue.

Good luck, and I hope that does fix your problems.

I have had no problems with mine over the past 4-5 years that I've had it. It has run perfectly with every kind of ammo I have tried, including subsonic.
 
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Found the issue. The firing pin spring was lodged in the firing pin channel instead of sitting (and staying) around the pin itself. I had to stick a small screw driver in there to pull the spring out. Cleaned out the firing pin channel and put a new spring on the firing pin. Will test tomorrow at the range.
 

JAA

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Gentlemen: I’m new to your community and obviously a couple years late to this thread but I’m experiencing the same problem with my CMMG 22lr conversion kit ie down here in PA we call it “doubling”. Pull the trigger1 time and send 2 rnds down range. It started after 100 rnds.
Everyone is telling me it’s the trigger but have changed them out and it continues.
Went back and forth with both CMMG & ALG. CMMG provided an RMA and a new conversion kit is on its way.
Was anyone able to determine the cause of the problem?
Doesn’t look like Taccom sells the reliability kit anymore.
Thanks for your help.
 

mac1911

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Gentlemen: I’m new to your community and obviously a couple years late to this thread but I’m experiencing the same problem with my CMMG 22lr conversion kit ie down here in PA we call it “doubling”. Pull the trigger1 time and send 2 rnds down range. It started after 100 rnds.
Everyone is telling me it’s the trigger but have changed them out and it continues.
Went back and forth with both CMMG & ALG. CMMG provided an RMA and a new conversion kit is on its way.
Was anyone able to determine the cause of the problem?
Doesn’t look like Taccom sells the reliability kit anymore.
Thanks for your help.
Basically what happens is the BCG is not setting the trigger when the bolt chambers the next round the hammer follows and appears to have enough energy to set off the next round. I had a old bolt action 22 that would do similar?
My Tacticla solutions 22lr upper would not work with some early AR milspec triggers--- They had a slightly different shape. Then at some point the design changed. Oh and My Tacsol upper would not work with my first RRA NM trigger but works with all the newer ones?
 

JAA

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Thanks for taking the time to help out. So if I understand what you are saying is that since I changed out my trigger group (went from ALG’s ACT to CMMG’s AR 15 trigger group) the problem is my BCG. Correct?
Therefore by changing out the CMMG BCG for a new one, the odds are in my favor the “doubling” should go away?
Any thoughts as to why it would take ~100+ rnds for this problem to surface?
Thanks again
 

mac1911

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Thanks for taking the time to help out. So if I understand what you are saying is that since I changed out my trigger group (went from ALG’s ACT to CMMG’s AR 15 trigger group) the problem is my BCG. Correct?
Therefore by changing out the CMMG BCG for a new one, the odds are in my favor the “doubling” should go away?
Any thoughts as to why it would take ~100+ rnds for this problem to surface?
Thanks again
i cant say for sure , cmmgs design is a copy of a old design as are most of them
Troubleshooting the Atchisson Type AR15/M16 .22 Conversion Kits

Usually theres something that has to happen
 

JAA

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Mac1911
Thank you so much for the link. It was an interesting read. It confirms what other individuals have come back with.
I received my replacement Bolt Group from CMMG yesterday and hit the range today. Only had 2 incidents of doubling at the beginning of a 15 string run. After that the other 13 strings ran fine.
More range time needed to confirm the new unit will function properly.
Thanks again!
 

Eric H

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I've recently snagged one of these CMMG kits (within the past 2-3 months) and I've got about 2000 rounds through it, maybe more, and haven't had such an issue. But MAN do they get filthy. I've taken several new shooters to the range to use it and they've absolutely loved it.
 

jpk

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I've recently snagged one of these CMMG kits (within the past 2-3 months) and I've got about 2000 rounds through it, maybe more, and haven't had such an issue. But MAN do they get filthy. I've taken several new shooters to the range to use it and they've absolutely loved it.
22LR in general is dirty shit
 

JAA

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Mac1911
Thank you so much for the link. It was an interesting read. It confirms what other individuals have come back with.
I received my replacement Bolt Group from CMMG yesterday and hit the range today. Only had 2 incidents of doubling at the beginning of a 15 string run. After that the other 13 strings ran fine.
More range time needed to confirm the new unit will function properly.
Thanks again!
I am ~7 months into the "replacement" Conversion Unit and 1700+ rnds of various 22lr ammo thru it such as AM22, AE22, Champion 745, Remington 1622C and CCI Std Velocity and the "doubling" comes and goes along with FTE issues independent of ammo type and cleanliness and less to no CLP. I shoot this in Steel matches and sooner or later I'll be DQ'd due to the "doubling" and in the meantime my times can suck due to clearing FTE's. Wish there was another offering out there.
Would anyone know if the S&W 15-22 BCG would work in a std AR upper?
 

mac1911

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I am ~7 months into the "replacement" Conversion Unit and 1700+ rnds of various 22lr ammo thru it such as AM22, AE22, Champion 745, Remington 1622C and CCI Std Velocity and the "doubling" comes and goes along with FTE issues independent of ammo type and cleanliness and less to no CLP. I shoot this in Steel matches and sooner or later I'll be DQ'd due to the "doubling" and in the meantime my times can suck due to clearing FTE's. Wish there was another offering out there.
Would anyone know if the S&W 15-22 BCG would work in a std AR upper?
why not just get a SW 15-22 or a dedicated 22lr upper and pass that insert chamber thing along?
 

northny

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I have two conversion kits, one taccom and one cmmg. Both are used with dedicated .22 rim fire uppers and use better mag adapter with S&W 15-22 mags. Like an AR they like a little clp to run ( just not dry). I have between 2500 and 3000 rounds thru each. Have taken both to Appleseed shoots

I only run CCI SV in them and found both uppers to be fairly reliable. Only issue I ran into like yours was I had one lot of ammo (I tend to buy 1000 rounds of one lot at a time and dedicate that lot to one rifle) that started to have either a failure to fire or an occasional double or would run fine. Turned out I had a broken firing pin that was floating around. It could be short ( failure to fire 10%) long (double issue 1% of time or less) or just normal 89% of time . A new firing pin fixed me right up. I have spare firing pins now as not uncommon for them to break.
 
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