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CMMG .22 conversion kit quick review


Dec 17, 2019
For black friday I got myself one of the CMMG .22 drop-in conversion kits and a couple of boxes of the Federal black .22 for right around .025 cpr. My math was that, with the cost of the kit, i would break even shooting 1k rounds. It also seems useful for rough zeroing new guns/ optics, something that has always struck me as a waste of ammo. My goal is to stack only good quality 5.56, while burning the cheap .22 at classes.

The first time out i had a fair number of failures to extract that frequently lead to double feeds. I shot right around 250 rounds. Out of a 11.5 barrel POI was a couple inches lower than zero, but was able to stay on a steel silhouette at 100yds. Good enough.

I disliked how the bolt does not activate the Bho, so when you drop an empty magazine, the bolt closes, and you must charge the rifle. This changes my mag change routine. I also found that the bolt cycles WAY faster than normal. While quite fun, I had to remind myself to slow down during fire and movement drills, and not just impatiently doubletap every shot.
When cleaning, i found that the chamber adapter had split. CMMG quickly and politely replaced it.
The next time out i shot around 200rounds, this time mostly out of a 7.5" pistol, with only a couple assorted malfunctions, much less than before. Flash and report wad quite deceptive, making it a bit of a shock going back to 5.56!

I will continue to use this kit, and do feel that it will help me meet my goals of shooting more, despite its few problems.


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Never tried the adapter set, but I have a dedicated 22lr upper that I built around a CMMG bolt/barrel and it runs great. Over 1k rounds through it so far without a failure.
I bought the same conversion kit last fall for a S&W MP-15 - lots of fun shooting, especially at under 4¢ a round. Mine functioned better with the CCI Blazer 40 gr. RNL than Federal black (which seemed to be under powered and had fail-to-eject issues) - CMMG recommends using a 36 grain plated bullet, but I haven't tried them.
One thing to remember is to keep it lubricated - it likes to be run wet.
Nope - I bought this to save money and already have (6) 25-round magazines. I knew the bolt wouldn't stay open after the last shot and it's not a big deal.
They stop the jam o matic from happening. Blag dog are same if not cheaper. Return the others The cmmg are shit mags. I would compare them to promag.
I don't have any jams or failure to feed, failure to extract or failure to eject with the CCI Blazer ammo and the CMMG magazines. As I said, run it wet and there aren't any problems.
I agree about the Promags, though... I stick with Magpul anytime I can.
Did you write this on another forum??

I like mine and have run many thousands through a couple uppers. Forget about accuracy past maybe 25 yards. Good to learn fundamentals and to introduce new shooters without recoil. I have only 1 mag... I put the gun down, load a mag, put mag in, charge it w/ safety on and start my routine from there... not to break training/habits etc.