CMMG dedicated 22lr upper?

  • I'm looking at a CMMG dedicated 22lr upper to play around with on my AR.
    Specifically the MK4T, Anybody have experience with these?


  • They look to be pretty nice. Haven't used one myself. I have a couple spikes kits... and they are temperamental.

  • I'm going to give it a try...I'll post how it works out

  • Excellent! I look forward to the report.

  • Banned

    Yes, let us know how it goes. I had a .22 AR upper for a bit and it certainly served its purpose but I haven't used it in a while. I am interested to see how you like the dedicated CMMG.

  • Well, accuracy wise the CMMG upper does good, however I had a lot of malfunctions.
    All were failure to feed. I was using CCI Mini Mags, tried a couple of different magazines and it didn't help.
    It would pick up the bullet but it wouldn't feed into the barrel causing it to get stuck sideways. Destroyed the rounds either by denting the case or bending it at the bullet.


  • @deltawiskey

    Get yourself the Redi-mag adapter and use the s&w mag's it will due wonders.

  • @jibnast said:


    Get yourself the Redi-mag adapter and use the s&w mag's it will due wonders.

    I will look into that, thank you!

  • I've always used the black dog machine mags with great success.

  • @orkan Yeah, me too...I use Black Dog in my Sig 522, they work perfect! I tried them in this CMMG conversion with no luck.

    I contacted CMMG tech support and they sent me a video instructing me to do this:
    "This should be equally effective whether it’s the dedicated upper, or the conversion kit."

    I'm quickly loosing confidence in this company! Since I have the dedicated upper and not the conversion kit my bolt doesn't look like the one in the video...I can't believe their tech support doesn't know that!???

    More to follow...

  • This is what the front of my bolt looks like

    The part that they are "buzzing out" must be what fills in the .556 chamber for the bolt type conversions.

    I'll post what they have me try next...

  • Man, that is idiotic.

    I consider myself fortunate that I was able to get 2 different 22AR's functioning near 100%. I will never significantly change them unless they break. I went through thousands of dollars in parts trying to get them right before succeeding.

  • So the latest guidance from CMMG Tech support is for me to perform the "buzzing out" procedure on the chamber of my barrel. This just doesn't sound like a good idea to me...

  • What a bunch of clowns. Well that pretty much settles that in my mind.

    If you want to shoot some video, or take some detailed pics of the issue you're having, I'll help where I can.

    I have spent a ton of time working on ciener and spikes tactical kits over the years. Depending on the issue you're having, I should be able to help if I can see closely enough what is happening.

  • @orkan Thanks! I will work on it this weekend!!

  • Ok, I used my Dremel and some polishing compound on the feed ramp and the slides for the bolt.
    The reliability was greatly improved, especially with Federal auto match ammo instead of CCI mini mags.
    I'm still seeing this in approximately 1 in 10 rounds:
    It will pick up the live round and feed it into the barrel, but still have the spent case.

  • Extractor.

    I'm betting you need to tune the extractor. The case is getting drug back out of the chamber, and then probably crashing into the ejection port and flying back into the works.

  • @orkan thanks for the diagnosis! I will do some Google searching on how to do that...more to follow!

  • Good luck with that! I bet Wayne and I know more about tuning extractors than any four other men living. ;)

    It has to do with the angle and shape of the claw, you can shape it so that the case "flips" one direction or the next. If it's riding high, you can take the other side down, to let it flip out sooner, etc. It's about 30% science and 70% art.

  • @orkan I was hoping you would give me some Tips! I don't have any experience with this stuff...

  • Slow motion camera helps a lot when tuning. So you can see what's hitting where.

    Run the bolt manually. Slow, then fast... watch how everything moves. See where it's hanging up, see what's hitting where, and when. Then consider the angles/shape of the extractor claw. You can get that brass to move where it needs to go by shaping it.

    It helps to have a few extra extractors laying around. ;) Might take a little trial and error.

  • Do you have any experience with the TACCOM Extreme extractor?

    Maybe instead of trying to tune my extractor I should just try to replace it??


  • Never used that one. Buying and trying others is a good idea, since if you have to modify one, you may need a replacement if you make a mistake. ;)

  • Update!
    As I mentioned earlier, I "buzzed" the chamber like they suggested in the video and polished the feed ramp and the bolt slides. This did improve reliability a bit, but it was still terrible.

    Following Greg's suggestion of it being an extractor issue, I decided to replace the extractor instead of trying to tune it. After some looking I decided on the "Extreme Extractor" by TACCOM. They had a sale for Black Friday going with free shipping and something like 20% off so I ordered the "Reliability Kit":

    The kit worked!! I took the rifle to the range and it performed flawlessly for 100 rounds! : )
    I didn't bring any more ammo with me as I wasn't expecting to need it, so a longer term review will be coming.


  • Good news. Glad you've got it sorted!