Light Strikes: CMMG AR-15 22lr barrel

I recently built my first dedicated .22lr AR-15.  Since I already owned a CMMG .22lr conversion kit, I decided to just order the .22lr barrel from MidwayUSAcom with the barrel adapter.  As soon as I had it all installed I noticed light strikes on the .22’s.  So I reached out to CMMG.  They had no advice, so I consulted some forums and found that others were experiencing similar issues.

Long story short, I disassembled the entire gun and found the problem when I inserted a dummy 22lr cartridge (blue).  Essentially, the collar that came with the barrel had a ramp that prevented the cartridge from seating properly.  So I removed the adapter 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 someone!

On the left is the original adapter that came with the CMMG conversion kit.  On the right is the barrel adapter attached to the barrel:


Here is a picture of the adapter (reshaped)


…and here it is removed from the barrel.


Everything is installed:

Next insert dummy round:
Bolt closed with dummy round:

Extraction of dummy round:

Other pictures after mod:

Shooting my dedicated AR in a Steel Challenge match:

Good luck,


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5 thoughts on “Light Strikes: CMMG AR-15 22lr barrel

  1. Rob,

    thanks for this post . I was having a similar problem with light strikes on the CMMG 22 LR. I performed this mod and it fixed my light strike problems. However, after modding the feed ramp, I started to have fail to eject problems..and only after the round was actually struck by the firing pin. to remedy the issue, I had to tweak (very little) the ejector grove in the barrel so that the ejector could get a good hold of the brass.

    after these 2 mods, my CMMG upper runs like a sewing machine.

    Mag dumps for everyone!

  2. I recently received this e-mail from Mike G:

    Dear Rob I want to thank you, I finally did your mod and my rifle shoots everything. I have cut the recoil spring for sub sonics the firing pin spring is lighter and I have a dowel in the buffer tube to push against bolt to give tight fit. I have an RRA 2 stage triger and I am finally happy with this rig. I cannot believe the difference the indentation is so much pronounced, I also lessened the firing pin face so its not so large. My rifle shoots every ammo and no FTF OR FTE. I am very happy:)


    PS: I was reluctant to do your mod because I looked at all the forums and nobody has done this mod why has nobody taken to this. I am sure that a majority of the problems with light strikes on the CMMG SS 22 bolt and collar is because of this feed ramp. Also I believe that it was probably during the chroming stage that increased the amount on feed ramp. I filed very slowly until I could barely remove the collar without extracting case with feed ramp. no more.

  3. Rob is correct.
    Out of the box, my dedicated CMMG 22lr would not close the bolt fully on a round by at least the thickness of the cartridge rim. First round manually fed o.k. do to full/ harder stroke of cocking handle but second round on auto would stop slightly short.
    The barrel collar was removed and positioned over the barrel. I then tried to chamber a round lightly with finger tips. On inspection, the feed ramp was too high and not ground concentric to the chamber. I had to press the round past the ramp and even then if I spun the collar, the round turned with it.
    A good few strokes of a fine half round ‘rifle file’ brought the top of the circular ramp groove to centre and reduced the height until as Rob explained, removing the collar doesn’t pull the round out of the chamber.
    p.s. I have only C.C.I Stingers left to try this with, but will report back on my findings

  4. O.K., I tried the Stingers and it was very unhappy with these.
    Some have said that the longer case and forward position of the Driving band on the slug should not affect my rifle or similar. Well, my CMMG ‘hated’ these. The Extractor claw ended up with peening marks on it’s front lead in face, which I had to file smooth.
    So my next choice was CCI Velocitors. Not bad but these would jam the odd empty up in the bolt resulting in the need pry it out or strip the bolt out to get it removed..not good!
    An then ‘Bingo’, my only remaining ammo was CCI Mini Mag and it was brilliant. This was what it needed. It had more felt ‘jolt’ to the action, sounded louder and cycled without a problem. An I had thought it was a ‘poor cousin’ to the others from CCI…wrong!

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