CMMG upper...help

[TriggerMeister]

@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".

[TriggerMeister]

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.

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 )

[Trgt]

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!

[TriggerMeister]

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.).

[Diskea]

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)

[shadow65]

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

[onegtalon]

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)