CMMG upper...help
 

Hello to all.....got a small problem with my CMMG complete upper , just a bunch of faliure to fire with diff. types of ammo , looks like light strikes..... ??

ammo: fed 40grns , cci hp , and rem golden
mags : black dog 10 rds (4)
lower : box stock AR15 lower , works great with a 5.56 upper in place

I could not get thru a 10 rd mag with out having at least 4-5 failure to fire

the fed 40grs bullets were real bad , I went thru a few mags and not even one round would fire ! (put them in my handgun and all went bang , not the ammo)

the rem golden bullets were the best of the bunch , with maybe 8 out of ten would fire fine

the cci velocitors were not much better then the fed ammo !

when it went bang....the groups were good at 25yrds

I got so mad at it ..I almost went to the truck to grag a pair of nippers to cut a coil or 2 off the firing pin spring....thought I better ask a few others first if they have had the same trouble before cutting on it !

total rounds 1st trip out...about 80 , and all the same trouble , break in ?

2nd trip (today) about 300+ rounds , should be broke in by now ?

help / input would be great.....thanks in advance...

Semper Fi
(can't get the darn photo thing to work...sorry)

Maybe a new stronger hammer spring, also you don't have a polymer lower do ya?

Don't mess w/the CMMG upper - its got a lifetime warranty. Contact Dave aka Shadow65 here on Calguns, he can assist you if you need to send it in or troubleshoot the system.

I owned two and them been flawless.

Lower is a SOG , with a DPMS lpk , good solid lower with stock factory parts , maybe a stronger hammer spring ? it works fine with a 5.56 upper...

may have to send it in...don't know yet , would 300-400 round count be good for a break in ?

I had the same problem with my CCMG upper over a year ago. Shot Federal, Winchester and Fiocchi .22LR ammo with similar results.
Shadow65 recommends still using a buffer and action spring even though it is not needed with a 22 upper. I also recommend using a Taccom Pressure Plug.
If the problem persists then send it back to CMMG. They might need to buzz the chamber and check the firing pin.

Thanks for the input....using a h-buffer with stock carbine spring

what is a Taccom plug ?

did yours settle down or did it need a bit of work ?

Thats a bummer man. i cant remember the last malfunction mine had, and i shoot several thousand rounds a year through it

+1 Taccom pressure plug. Get the reliability kit with firing pin.

Robert

Here's the linK to the Pressure Plug.

I sent my upper back to CMMG for them to check out. According to the repair order, the light strike misfires was due to the cartridge was not seating all the way in the chamber. They "buzzed" the chamber to smooth it out and cleaned & checked the firing pin. I ordered and installed the pressure plug as insurance against light strike misfires. The upper has been 100% reliable since.

Thanks much for the link

when I pull the CH all the way back hard... I get a bit of movement of the front collier (1/8" maybe)....the pressure plug may be the fix I need...

Hi

I had the same issue a few weeks back, I was lucky to have 2 other uppers handy.
I change uppers, mags, entire bolt assemblies, springs, firing pins.
I also rechecked my lower assembly and buffer spring.

End result was firing pin. Switching the pin solved 99% of all light strikes.
I changed the firing pin to one that was consistent and the rifle fired.
I still get one light strike every 50 to 100 so I feel additionally a stiffer buffer spring and H2 buffer are needed for adjustable stocks but for the A2 stock the defaults work fine.

Taccom reliability kit is your best bet. For one for my CMMG dedicated and all the problems went away.


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OneGtalon

Make sure to put a tiny drop of lube in the extractor pin? Mine wasn't closing completely*cuz crud got into it. So it would have light strikes

thanks to all for the help and info .

Most likely is CMMG has too much head space on the bolt.
This is nothing new.
The TACCOM Reliability Kit will solve a lot of issues with light strikes and feeding.
The TACCOM Firing pin is slightly longer, comes with shims to adjust length, and is has a smaller, angled tip for more reliable ignition. It's also hardened so much less likely to break.
The Extreme extractor has a better angle on it and gives better, more consistent extraction to make upo for the excessive head space on the bolt.
The Pressure Plug keeps pressure against the rear of the action to give 0 movement under recoil which can absorb energy from the hammer strike resulting in light strikes.
It does need to be used with a buffer and spring.
This is the best up grade I have tested for solving the Atchison type conversions issues.
I have one if you need it.
Dave N

Thank You Sir , I already ordered a complete kit , good to know the info given by others is spot on , its a nice upper and I like how it shoots (good groups at 25yds!)

looking forward to giving it a good run when the parts show up.

Thanks to all for the help/info..............range report coming soon...

i have a ccmg upper on a NFA lower i havent shot yet....should i get the plug..should i expect some problems??

Only way to know is to shoot it first. The kit IS cheap so it wouldn't hurt anyway IMO.


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OneGtalon

You need to shoot it first... Though, i will say... The kit is worth while IMHO.

Good luck getting this resolved. I have had nothing but problems with my CMMG rifle and even worse luck with their "customer service" staff.

It wasn't always that way. Sorry they are giving you problems. I would help but I'm kinda on the outside now.:rolleyes:

The TACCOM Reliability Kit will improve any Atchison type conversion or dedicated bolt.
Dave N

range report with the Taccom kit in place.

1st off...I thought the firing pin was a bit loose fitting , called the Taccom dealer and asked a few questions , he took the time to explain all to me...sounded good , so off to the range I went...

winchester 36grn....still had a few light strikes , much less then before the kit

federal lightning 40grn....still a few light strikes

cci velocitors.....100% (before the kit it was maybe 50%)

Rem golden 36grn (the 525 bulk packs)....almost 100% with only a few light strikes , out of 300+ rounds I had only 7 light strikes and all but one went bang when tried again..

I have to give the kit a big thumbs up :)

I ordered the complete kit , and belive it was woth every penny spent ....

thanks to all that refered me to the TACCOM kit , guess now I'll need to stock up on more ammo (the good ol' 525 bulk pack seem to work best)

What's wrong with using a .22LR CMMG upper with a poly lower. I purchased the complete (w/butt stock) lower for $109.00 two months ago, and just found out that CMMG has shipped my left handed Revo upper today (!). Very excited. I thought I would just mate them and be happy with fun, low-cost shooting. Is this not a good/dependable config?
And if the upper is specifically designed for .22lr, is that little insert part useful?
Thx,
B

So long as the upper mates to the poly lower, there shouldn't be a problem.

Another thing to check when having light strikes is the bolt rubbing against the bolt catch. That will slow the bolt down and could keep it from closing completely.
Make sure the bolt is going completely closed or you could have an OBD.

I also suggest buzzing the chamber on the CMMG.
Go to the CMMG YouTube and you will find a video on the procedure.
Dave N

CMMG Buzzing youtube



I stickied this thread there is alot of great information here

I had the same issue, if it's a notched hammer the cmmg will not like it. I also bought the pressure plug. Hopefully that helps

The Pressure plug goes along way to reducing issues...

All your info on CMMG products
http://www.youtube.com/user/CMMG

Got a CMMG upper and have the TACCOM kit.

The TACCOM parts say disassemble bolt as direct by mfr., but the CMMG documentation says don't disassemble past field strip so I don't have instructions for that.

I don't want to cheese my CMMG parts, anyone got a link to info on how to get it apart to replace/adjust firing pin and replace extractor?

Thanks

Its like the AR bolt assm.

Firing pin - pull the retainer pin out from the side and the firing pin comes out along with the spring.

Extractor - you need to put some pressure on the extracor inwards and drive the pin out, then slowly allow the extractor to come out with the spring.


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OneGtalon

Does anyone know where to find a Nordic upper (sorry I know this is regarding CMMG stuff) I haven't been able to find for some time. If anyone has a Nordic upper 18" I'd be very interested. thanks

@green_grunt: I had the same issue. Essentially, the collar that came with the barrel had a ramp that prevented the cartridge from seating properly...which caused the light strikes because it buffered firing pin striking the rim. I removed the adapter (with the ramp) from the barrel and used a round file to reshape the adapter until the cartridge, seated flush with the breech-face. Don't be timid, since there is quite a bit of extra material and just go slow, little at a time. In fact on some of these there is so much “extra” feed ramp that you think that “can’t be right”. Take a little off at a time and when you can remove the collar without pulling the dummy bullet out of the chamber you are done! At that point you should polish the feed ramp to remove any tool marks and give it a nice mirror shine. That solved all my light strike problems. Hope this helps...

Got pics of the problem described above on my blog at woodhousellc.com. search for "cmmg".

Like paintballdad said most of these problems are due to the cartridge not seating in the chamber, but it's due to the feed ramp being too long and not the chamber itself. I'm slowly thinking this is a very common issue. The only reason I found it was because I had the 5.56 adapter and was able to compare the two (picture: linK )

I just started using a dedicated CMMG 22 upper. It was flawless with CCI standard velocity. But was really bad with with Winchester Xpert HV (would sometimes fire first one from mag, sometimes not, and nothing after). I'll have to see if these cartridges are sized differently, I was just assuming it was some different in cartridge construction/content combined with the SSA 4.5# trigger on the lower I was using. ... I will definitely try tips above, thx!

A friend of mine, who also had the light strike issue after his .22 upper build, is running his rig with a Geiselle(sp?) trigger and Federal bulk pack ammo. I love my setup and it runs so good I trust it even for steel challenge matches. Most of the time I run all stages without a single failure using bulk ammo (GB, Fed, etc.).

Pull out your bolt and see if you can seat a round flush in the chamber, either use a dummy round or a live round with extreme prejudice, or if you have some non-malformed .22 brass sitting around. My cmmg wouldn't seat rounds all the way in due to a small piece of metal from the feed ramp, I buzzed my chamber and sanded the medal a little to follow the lines and it fixed my problem, no issues in 4000+ rounds (non ammo related)

One of the issues with CMMG is tolerances being off.
When tolerances are off, it needs to be corrected.
That was what happened with the mags also. They worked fine in the beginning. Then tolerances went off and caused followers to hang up.

Dave N

FYI (not sure if mentioned before) but I had a dedicated 22 upper that was always jamming and FTE, fail to chamber... It was the Magpul BAD lever..it never allowed the bolt catch to fully seat...(it rubbed against the cmmg upper all the time)

Got rid of the lever and now it shoots everything... (I do have the reliably kit installed BTW)