View Full Version : CMMG .22lr Conversion Malfunction

04-24-2012, 9:11 PM
So i had my first AR malfunction today. The CMMG kit has been great as long as i use Stingers or Minimags.

I fired off about 50 Minimags and on the 6th mag i started having some ejection problems. I then switched to the Singers and the second shot this happened. Im not sure what ended up grazing my left arm but it sure didnt feel good.

Did i just get some bad ammo? I was able to easily tap the bullet out with a brass rod and there doesnt appear to be any damage. Should i give it another go?


04-25-2012, 9:46 PM
How many rounds did you shoot before between the last cleaning and when this happened? Mine starts to have ejection problems after 300-500 rounds depending on ammo. After a clean of the bolt and carrier rails it runs smooth again. Maybe fouled up bolt, rail, and collar, which lead to the bolt slowing down and not fulling chambering a round then OOB discharge and/or weak rim. No clue what the chamber pressure difference between the stingers and normal stuff. I'd be weary to shoot again with out some eye protection, rope and a barrier to hide behind.

04-26-2012, 8:30 PM
That was on my 5th mag of the day so less than 50 rounds. The whole kit has well under 500 rounds through it. It had been freshly cleaned after a flawless performance during its previous outing.

04-27-2012, 3:57 PM
Looks like there may be some carbon build up.
I wouldn't recommend using Stingers in the conversion. The case is slightly longer and can cause feeding problems.
Combine that with carbon build up and you can have an OBD
Dave N

05-06-2012, 12:47 PM

I think i may know whats causing it. The last modification i did was adding a cmmg 2 stage trigger. The hammer spring is significantly mre stiff and may be causing the cycling problems.

Ill try swapping the cmmg spring for a standard one to see if that helps.

05-06-2012, 1:01 PM
Since it was an OBD I'd clean the bolt really well... It looks like theres a ton of carbon build up.

As for cycling problems I'd try/do these things:

Check the spring (like your doing)
Try using some other copper washed .22LR such as Federal Champion...
Try using a round hammer instead of a notched hammer
Make sure the conversion is well cleaned & lubed
Are you running a model of bolt that has/uses a Forward Assist Adapter OR a BHOA? If so I would try removing them..
Finally, I would probably contact CMMG... They will help you get it running if all else fails.

05-06-2012, 1:18 PM
Just out of curiosity does anyone know what CMMGs official position is on rounds like the Stingers? What are you using for lube? I only only use RemDriLube in all my .22 rimfires. I never put any wet lube in a .22. Have been using the stuff for many years and it provides great lubrication without all the mess of wet lubes. Hope you get it figured out.