CMMG .22 LR AR-15 Conversion Kit Review

The days of blowing through a case of .223 ammo ended for a lot of us some time around the last presidential campaign. Until that point, the ammunition had been relatively affordable.

Even though prices have backed off the historic highs of the ’09 buying frenzy, .223 rounds are not as cheap as they once were. Also, double-digit inflation in ammo pricing is now a reality thanks to the increases in the metals markets.

Thank goodness for the .22LR, eh?

Several companies offer .22LR conversion kits for the AR15 platform. One of the most affordable kits is offered by CMMG.

The Kit

The CMMG kit I tested came with an entire bolt assembly replacement and one magazine. I also picked up a second magazine (also known as pure evil…more on that later.)

The kit comes with easy-to-follow directions, which you probably won’t need anyway. To install the kit, you simply remove the old bolt carrier and install the CMMG carrier. It takes all of 10 seconds to accomplish.

A few notes about the kit. First, the CMMG conversion kit is designed for 5.56 chambered guns, not .223 chambered. Most of the AR15 rifles I have ever seen are chambered for the 5.56, but make sure yours is before running off to buy one of these kits.

Second, make sure you remove the green rubber end cap from the end of the conversion kit before installing. This should be obvious, but I don’t want anyone trying to jam the thing into your upper.

Last, this kit works for direct gas impingement guns only – no piston guns.

There are a few other suggestions for accessories not to use for best performance at the CMMG page. You should check those out before buying.

Range Time

The .22LR is a light shooting cartridge. Just how light struck me when I started firing them out of my AR.
I had been shooting 55 grain Remington FMJ in a DelTon AR15 for a good part of the afternoon, when I broke out the CMMG conversion kit. When I pressed the trigger for the first time, I just started laughing.

No one can describe the recoil from a .223/5.56 as “harsh” or “punishing.” But when running .22LR from the same gun, the absolute lack of recoil is amazing. If you have someone that is very recoil sensitive, and even the .223 is a bit much for them, get them started with a .22LR conversion kit.

I ran both Winchester and Federal rimfire ammo through the rifle, and both gave average results at 50 yards. The AR15 I was shooting was sighted at 50 yards, and with .223 ammunition, produced tight groups.

Both .22LR loads shot low by several inches, which was not surprising. Groups were not tight, with rounds striking in roughly a 9”-10” circle. The Winchester loads were the most scattered, while the Federal rounds were slightly more consistent.

Neither load would have been suitable for taking a rabbit or squirrel with any degree of confidence. If I was planning to try to use the gun and conversion kit for pest control and varmint sized game, I would definitely have to try several different premium loads to find one that was much more accurate.


The CMMG conversion kit was reliable with one magazine, but completely unreliable with the second.

The magazine that shipped with the kit was very loose when seated in the gun. It would wobble in the magazine well, but seemed secure. Though I had my doubts, this magazine proved very reliable. I experienced only one malfunction with this magazine: a double feed after the first three rounds fired. After that, it was 100%.

The second magazine, however, was the exact opposite. This magazine was very tight in the magazine well, and had to be forcibly stripped during just normal mag changes.

I experienced nothing but problems with the second, tighter magazine. With this mag in place, double feeds were the rule, not the exception. Of the 26 rounds held in the magazine, I experienced at least 10 double feeds per load.

After two magazine loads of pure fail, I just stopped using that mag and enjoyed the shooting.


At about the same price as 500 rounds of US made .223/5.56 ammo, you can pick up the CMMG conversion kit and 500+ rounds of .22LR to feed it. At that point on, you’re saving about $140+ on every 500 rounds fired. So, from a pure nickels and dimes perspective, the conversion kit makes a lot of sense.

For me, the drawbacks to the kit center on reliability and accuracy. With the right magazine, the kit worked fine. However, with the wrong magazine, the kit was unusable. I suspect that I could have made the tight fitting magazine more reliable with a hand file or Dremmel tool, but I shouldn’t have to. If I buy your product, I expect it to work.

Accuracy is more of an open question for me. Some of the finest rifles in the world will give crappy groups with excellent ammunition from one manufacturer, and beautiful groups with ammo from another manufacturer. It is one of the great mysteries of life.

I suspect that the AR with conversion kit will produce tight groups if I experiment and find the right load(s). It would certainly be a fun process seeking out the best loads for the kit.

At the end of the day, I think the kit is a worthwhile investment as long as you know the potential downsides.

[ Richard Johnson is a gun writer, police trainer and really bad joke teller. Richard also writes for Guns, Holsters & Gear, Human Events and BlueSheepdog. ]

Richard Johnson

An advocate of gun proliferation zones, Richard is a long time shooter, former cop and internet entrepreneur. Among the many places he calls home is


  • arisocka

    First…i love the perocity on the left end of the weld on the fifth picture. Stick welding and a bcg don’t sound like the best of friends to me

  • Jason

    There are actually little tabs on the mags that you can file/dremel down to fine tune the fit. It’s very quick and easy. Once I did that, and once the bolt was broken in, the thing just worked like butter. I really can’t say enough positive things about the CMMG 22lr system.
    I later purchased an upper from them and was able to simply drop the bolt in and fire away with more acceptable accuracy than the kit alone allows for.
    However, I did find that the Tactical Solutions complete upper to be more accurate out at 100 yards and eventually switched to that. Still, the CMMG system as a whole is better.

  • DRod

    I have the Cienier kit (identical to cmmg) and it cycles 100% in my Colt. With one caveat. The Magpul BAD lever pushes the bolt catch up just enough to ride the bolt and cause problems. Holding it open or removing the lever proved to fix the issues and allows flawless functioning. Mines also quite accurate, relatively speaking. Two inch groups of 28 rounds at 75′ (indoor range) are not hard.

  • DRod

    To add: All plated bulk packs function 100% in my experience. Lead nose are a no no, IMO.

  • Dusty

    Very interesting. Thank you.

    I am comparing this to my Ruger 10/22 carbine. I added a bedding kit which consisted of a bunch of stick-on pads, two (a set) of shims in the trigger group and ‘oversize’ trigger module mount pins. Also a polymer bolt stop which quiets the gun a lot. A 4-power ‘big rifle’ Bushnell scope in a bubble-pak from Wal-Mart. A coat of antique walnut polyurethane oil-base varnish for the bare wood and two more coats of clear satin finish, all wood surfaces (and a month to fully cure). Total at the time, two or three years back, less than $200 or maybe $220.

    The Ruger gives 3 to 4 inch groups at 50 yards, ignoring (don’t know, can’t see the holes in the target until after, just shoot 12 and disregard) the two ‘fliers’. If I shoot “Winchester Super X 1300 FPS” (copyright, name & everything) I can easily get groups under an inch at 50 yards. (No fliers if the barrel is even a little warm.)

    I shoot a DPMS (AR-10 pattern) in 308 and a lot of other guns (target) but just for fun. The cost of an AR pattern 22 LR rifle or upper seems excessive. I think I will not do that. I can see that I would be very unhappy with the kit you reviewed. Thank you again.

  • Chris

    Nice review.

    It’s never going to be accurate though without a dedicated .22 barrel with the right diameter and twist rate.

    Good plinking gun!

  • mark

    You may want to give Aguila 22 LR 60 gr sub sonic a try. Smells a bit “different” but groups better than anything I’ve tried. Really think it has something to do with the twist rate/bullet weight relationship.

  • Arifonzie

    “First, the CMMG conversion kit is designed for 5.56 chambered guns, not .223 chambered”
    I was always under the impression that they are the exact same thing, just different names
    .223= imperial(American) 5.56mm = metric
    Am I wrong?

    • Pontiaker

      Yes and no, the external dimensions are almost exact but,
      1) The brass is usually a little thicker on military 556 stuff
      2) Guns chambered for .223 have a shorter throat
      3) Also sometimes have different/tighter head spacing
      4) 5.56 is sometimes loaded hotter from the factory, this combines with the shorter throat and head space can cause excessive pressure. So using .223 Rem ammo in a 5.56 gun should be fine.The other way around COULD, but not always casue higher pressures and problems associated with higher pressures.

  • Brice

    The big problem with drop in kits like these is barrel twist rate. Standard twist for .22 is 1 in 16. Lots of ARs these days are 1 in 7. Combined with the low quality of .22 bullets and their soft construction, this can be a recipe for horrible accuracy. Although they are more expensive, when I get a .22 kit, it will be a full upper. Point of impact is going to change anyway, I don’t see any benifits to using the same upper and all kinds of down sides.

  • Josh

    .22 LR has a diameter of .222. .223 has a diameter of .243 . So when you shoot that 22 through a .223 barrel you get the effect of the bullet bouncing around just a bit. But enough to turn accuracy to crap.

    • Pontiaker

      Your .243 number above is a misprint right, you mean .224? .243 is the bore size for .25 cartridges. The bore size will always be smaller than the bullet going down the pipe so the rifling will actually work! lol. You might want to go read up on your cartridges.

      All these bullet sizes you mention above are fine in a .223 or a 5.56 since the true bore diameter of guns chambered in both of these cartridges is actually .219, so no bullets will be bouncing around down any barrel, lol.

  • gunslinger

    awesome review. I’ve been looking to get a .22LR conversion for my AR. I already have a 10/22 with 3 of the 10 round mags (excited about the official 25 or 30 round mag) so i don’t “need” a 22 rifle.

    although it would get my wife into the platform. she’s more of a pistol girl though.

    Steve, is there any chance of having multiple reviews on conversion kits? I’d like to hear different stories about how reliable they are. personally, i’m not looking for accuracy beyond 50 yards. It would bemore of a “plinking” blow off steam w/o spending 200 bucks on ammo.

    any more reviews/comparisons would be great.


  • Geore

    Good information, but left out one important item. I’m sure that many are going to post on this exact topic, but there are TWO reasons you are having terrible accuracy:
    – you are shooting .22 bullets out of a .223 barrel. The extra size margin is going to have the bullet not ‘grip’ the rifling properly, and it will be more equivalent to a smoothbore than a rifled barrel.
    – the barrel most likely has a 1:9 twist. This is great for heavier bullets at high velocity. But for lighter .22 bullets that have much lower velocity, the 1:12 – 1:15 twist is much more common. This difference in twist can also account for the increased inaccuracy.

    Someone might be better suited to get either a dedicated AR15 in 22 (like the S&W M&P15-22) or a full upper with true .22 barrel. The CMMG will ‘work’ but it wont be fantastic. Some might get very frustrated at the accuracy. Indeed, for training purposes I would highly recommend a dedicated upper, as the user will have a single base platform (lower) that they will be familiar with. Train with the .22, and deploy with the .223.

    Thanks for the great details though!

  • A dedicated .22lr upper will give much better accuracy. My CLE gives dime sized groups at 50 yards.

    The conversions have a number of hurdles to accuracy, such as the bore diameter and the twist rate of the barrel, a long jump to rifling, etc. They are great for some purposes though, and I’m guessing might do well at 25 yards on scaled targets.

  • cy

    I have the same kit. When at the range with friends, that is the most popular gun on the line. Everyone enjoys emptying a magazine of .22lr in a few seconds. no recoil and cheap to shoot. can’t beat that.

  • Richard Allen

    I assume that point of aim is different with 22LR than with 5.56 so wouldn’t you have to rezero when the AR reverts to its primary function. Shouldn’t the cost of that ammo be figured into the calculation, not to mention the hassle. Might not a 22LR clone be a better solution for cheap practice.

  • WeaponBuilder

    Somebody should post a review like this of the next-generation CMMG 22 Evolution Conversions.

    Their new 22 Evolution kits have a functional bolt-hold open adapter (works with newer ‘black follower’ magazines), which uses your rifle’s bolt catch to lock the bolt back after the last round in the mag is fired! It also has a functional bolt forward assist. Normally not a problem, but after your conversion unit has burned through 400 rounds of 22 LR ammo it gets pretty gummy and dirty, so a quick tap of the F.A. will make sure the round is fully chambered.

    Evolution kits also come with an Anti-Jam charging handle, which completely eliminates the problem of having 22 LR cases or live rounds jamming up inside a standard AR charging handle, and wedging itself around your gas tube that protrudes into the upper receiver.

    The videos speak for themselves (22 Evolution Kits):

    New locking bolt ECL / India Conversion:

    They also have an adapter available that functions fully-automatic for those with registered NFA weapons!

    I picked one of the standard $275 Evo Kits up for my personal use, and have come to realize the new CMMG 22 Evolution system is the best 22 LR AR platform on the market right now.

    First things first – Consider your barrel twist rate!

    – If your barrel has a 1:7 or 1:8 twist rate – Get the CMMG 22 Evo dedicated upper. $365
    – If your barrel has a 1:9 or 1:12 (A1 style) twist rate – get the 22 Evo Kit. $275
    OR get the new locking ECL / India 22 Evo kit. $335

    I have two AR-15’s – one is an A1 style 1:12 twist Government barrel – it works beautifully with the 22 Conversions, as do 1:9 twist barrels. However, my 1:7 twist Sabre Defense barrel makes a large ‘pattern’ rather than grouping… As such, I’ve bought BOTH a 22 Evo conversion for training with my A1 upper, and a dedicated 22 LR Evolution upper receiver which is nearly identical to my Sabre Defense upper (except with a much cheaper red-dot optic).

    I can now attend tactical training courses, and for the close range (under 50yds) training excercises – I can use the 22 Conversion, and when the course requires extending the range out beyond 50 yards, I’ll run the full 5.56mm.

    Over 75% of tactical carbine training course drills will be shooting within 50 yards, so this is a SUBSTANTIAL cost savings when attending tactical carbine courses and helps me better afford quality training.

    One common trend I’ve been seeing lately is that more informed customers are opting for Dedicated CMMG 22 Evolution Uppers instead of the ‘full factory 22 AR’ guns like the S&W and Umarex/Colt ones…

    I’ve seen a *LOT* of people buy a polymer composite Plum Crazy complete lower ($135), top it off with a CMMG 22 Evo dedicated upper ($365), and for $500 total you have the best .22 LR AR-15 setup on the market, and the lower is compatible with full power 5.56mm Uppers and NATO / STANAG 5.56mm magazines!

    Why pay $480 for a S&W 22 M&P clone when for $20 more you can get a 22 AR15 with MORE features, with a 1:16 twist, that can also fire 5.56mm by pushing two pins and switching uppers?

    If you have a 1:12 or 1:9 twist, the conversion will do just fine! Sure, it won’t quite be as accurate of a marksmanship tool, but 99% of the time people are using these guns for two things — PLINKING and TACTICAL TRAINING. The conversion units will do just fine for this…

    If you have a 1:7 or 1:8 twist, you’re going to want to spring a little extra for the full dedicated CMMG 22 LR Evolution Upper! You couldn’t be happier with such a setup for training use.

    The standard 25 round magazines with black followers work great with the Evolution Kits, but CMMG has also realized – one of the primary shortcomings of any 22LR AR-15 platform is the magazines. They’ve just recently remedied that as well by coming out with a modular magazine kit which takes things to a new level of customizability and reliability.

    I’ve since blown through nearly 4000 rounds between my two CMMG Evolution 22’s, and not to sound like a CrackDonalds cliche – “I’m lovin’ it!”

  • jpcmt

    @Arifonze, Not the same, especially at the neck/leade. The 5.56 has a shorter and different angle on the leade and this is manifest in the 22lr kit’s chamber end.

    I’ve put off getting one of these because I just don’t want to get crud in my gas tube and foul up my pristine barrel. Of course I don’t know how much more dirty it’ll get but I suspect moreso than with the 5.56 I shoot.

  • TCD

    Josh, I’m sorry but you have it all wrong.

    A 22RF barrel is .217 nominally, a 223 barrel is .224 and .243 is a is any 6mm or 243 round. Remember barrel bore diameters in SAAMI and CIP specifications reflect the “grove” diameter NOT bullet diameter.

    Happy Shooting,

  • Arifonzie:
    .223 and 5.56 are the same dimensions, but 5.56 rifles are designed to handle the higher pressures of the 5.56 NATO round. I’m not sure why it would matter in this case, though, since the .22lr is obviously nowhere near those case pressures. A .223 chamber should be identical (dimensionally) to a 5.56 chamber, and you’d think that the dimensions (as opposed to pressures) are the only thing CMMG should care about.

  • Adam


    .223 is loaded to a lower pressure than 5.56x45mm according to SAAMI. It is safe to shoot .223 in a rifle rated for 5.56, but not safe to shoot 5.56 in a rifle chambered for .223

    That and I have heard scuttlebutt around the gun store .223 chambers tend to be a little tighter than 5.56 chambers, but the only thing I know for a fact is that it’s loaded to a higher chamber pressure.

    It gets confusing when it comes to 7.62x51mm and .308 Winchester. Its the opposite case, .308 is loaded hotter than 7.62 NATO. Also, 7.62 is desitgned to feed more reliably in automatic weapons.

  • Gabe

    .223 (in my experience) seems to produce lower pressures than 5.56mm
    I think its sort of comparable to using .38 Special in a .357
    A gunsmith buddy of mine said you cannot safely fire 5.56 in a .223 firearm

  • 6677


    .223 in metric works out as 5.66

    5.56 in imperial works as: .219

    I believe the .223 is a shorter cartridge loaded to a much lower pressure. the shorter cartridge would still fit the longer chamber of a 5.56 but the 5.56 would not fit the shorter chamber of a .223

    That is from memory though and may not be correct

  • jd


    From Wikipedia:

    While the external case dimensions are very similar, the .223 Remington and 5.56x45mm differ in both maximum pressure and chamber shape. The maximum and mean pressures for some varieties of the 5.56 mm (different cartridge designations have different standards) exceed the SAAMI maximums for the .223 Remington, and the methods for measuring pressures differ between NATO and SAAMI.[5] The 5.56 mm chamber specification has also changed over time since its adoption, as the current military loading (NATO SS-109 or US M855) uses longer, heavier bullets than the original loading did. This has resulted in a lengthening of the throat in the 5.56 mm chamber. Thus, while .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, firing 5.56 mm ammunition in a .223 Remington chamber may produce pressures in excess of even the 5.56 mm specifications due to the shorter throat.

  • bp78

    Good start at a review but you lament the accuracy and never mention the test platform. Most ARs now are 1:7 twist which is much faster than the 1:16″ twist expected for a .22lr. If you try a slower 1:9″ or even an old-school SP1 with 1:12″ twist you will find much better results.

    Double-feed / nose up jams. The Anti-Jam charging handle is worth it’s weight in gold. You can take an old CH and fill it with some silicone to get the same effect.

    I’ve owned three of these, an original Ciener, parked CMMG, and now the polished stainless CMMG. The stainless is worth the premium, smoother running, stays clean longer, easier to clean.

    The .223 vs 556 comment? Did you have a source for that..? I find that odd, I’ll case-gauge my kit when I’m home with a 223 wylde JP case guage. I’ll bet it fits.

    The piston comment is misleading too. These things are straight blow back. If it’ll fit in your upper, it’ll run. You can even plug the gas port on a DI rifle and still have it work.

  • Pop N Fresh

    I went with a spikes st-22 upper and it will ring 4″ steel plates at 100m all day with aguila 38gr high velocity hp’s. Very accurate, tried the drop in bolt originally but it just wouldn’t group well.

  • I think Brice nailed your accuracy problem, due to the twist difference. Every time I re-consider buying one of these, or even reading a review for trivia’s sake, I think it’s a Bad Idea. The cost savings you mention are negated by the sheer PITA the reliability would cause. The accuracy is icing on the cake. If you need a trainer, budget for QD optic mounts, and switch to a dedicated gun (or complete upper.) There are enough to choose from these days, it shouldn’t be a problem to get squared away. Before too long, the cost savings will catch up anyhow, and then you have a quality kit. Or just get a 10/22 and modify it at will. Either of those two options is a significant step above a conversion kit. I don’t understand why there is a market in modern times for a deadly weapon which by its nature is failure-prone?

  • Sian

    Good lord that weld looks scary.

    @arifonzie they’re different enough that you don’t want to shoot 5.56 in a gun chambered for .223. You’re fine going the other way though..

    You might try some of the ‘tactical’ .22LR and see if that gives better accuracy, but the high twist rate of a AR barrel probably destabilizes a .22 proj all to hell.

  • dave

    >Last, this kit works for direct gas impingement guns only – no piston guns

    Actually, I’ve got a piston gun (CMMG FWIW) and as long as you remove the actual piston prior to installing the .22lr converter it’ll function just fine.

  • Brandon


    Would it be possible to make a special .22LR load with .243 bullets (or at least close)? Since CCI makes a load designed specifically for AR pattern rifles could you tweak the size enough so it would be more accurate but still feed in a standard conversion kit?

  • chris

    Josh what are you thinkin-.243?

  • Pop N Fresh

    josh, think you mean 223/5.56 = .224

  • Bob

    Back in the day I had the Colt Kit. Worked very well. Why did I sell it *sigh*

  • TCD

    Look Folks,

    I am really sorry BUT you cannot say things like:

    “….223 and 5.56 are the same dimensions, but 5.56 rifles are designed to handle the higher pressures of the 5.56 NATO round….”
    “A .223 chamber should be (<<<EDIT: W T F???) identical (dimensionally) to a 5.56 chamber, and you’d think (<<<EDIT: W T F???) that the dimensions (as opposed to pressures) are the only thing CMMG should care…"
    "… .223 is loaded to a lower pressure than 5.56x45mm according to SAAMI.
    "That and I have heard scuttlebutt around the gun store .223 chambers tend to be a little tighter than 5.56 chambers, but the only thing I know for a fact (<<<EDIT: W T F???) is that it’s loaded to a higher chamber pressure…."

    It is safe to shoot .223 in a rifle rated for 5.56, but not safe to shoot 5.56 in a rifle chambered for .223…"

    Please read my post above and look and any reputable reamer maker's drawing and you will not have to guess!!

    In the precision rifle world we cut a chamber to minimize brass stretching and to hold the round absolutely square to the bore of the barrel. Error in these specifications and you will have a rifle that WILL NOT shoot in the 100's!!

    There are many Remington 223 rifles that are shooting Much Higher pressures that any 556×45 round, with 1in7 barrels that are capable of shooting in the 100's!

    A 556×45 chamber is cut VERY generous when compared to a 223 Remington Particularly in the neck diameter! Shoot a 556×45 in a 223 chamber and You Will Have Very High Peak Pressures because the brass CANNOT expand to the designed spec to Release the bullet.

    Please! Please! Please! Do Not Perpetuate the VERY DANGEROUS MYTH that 556×45 is OK in 223 chambers!!!


    PS: All of you EXPERTS please post just how many years you have gunsmithed (TCD = 25 years total, 15 years as a professional and 10 years for my competitive rifles before), 223 & 556×45 chambers you have cut (TCD = according to my reamer logs 325 plus) and how many guns you have repaired re: this post (TCD = lost count in my FFL records so let's just call it LOTS!)…


    • Abe

      TCD needs to go back to school – he knows very little about the weapon systems he thinks he’s expert in.

  • Arifonzie

    Thank you everybody for setting me straight!
    Re: .223 vs 5.56mm differences.
    I was confused because I have a colt ar-15
    That is marked .223 on the receiver and 5.56mm on the barrel, purchased brand new like that, I wonder why?

  • MeAgain

    I’m far from an expert on these conversion kits but I’ll share my experiences.
    I ran into a guy at the range last year with the CNMG conversion kit and it had FTF with almost every round when he was running it in his Colt. Just for the hell of it it I tried it in my Bushmaster and S&W. I also tried a different brand of ammo and had the same results as he did.
    I read good things in general about CNMG’s kit and customer service so I figured that I would take a chance on one. The price was right (CDNNinvestments- about $160 on sale) and I ordered the stainless version. It works very well in my Bushmaster and S&W. No issues other than the occasional failure to go bang that you always experience when shooting bulk .22lr from Walmart. Accuracy is nothing to brag about but I got this kit to play at the local indoor range when it’s really cold out or I don’t want to drive 50 minutes to my outdoor range.
    I saw a pic somewhere of a severely leaded up gas tube from someone shooting a lot of non copper jacketed bullets through their AR with this kit. It was an extreme example but I make it a point to only use copper jacketed ammo and I always run a few rounds of 5.56 or .223 afterwards. It may be unnecessary but it gives me peace of mind.
    I also like the peace of mind of knowing that should there be an increase in ammo prices or lack of availability I can still shoot and train (somewhat) with my AR’s instead of having an 8lb paperweight.

  • Jason is dead-on accurate about the magazines. I have the stainless version of the kit that I got from, and when I sanded the tabs down so that the magazine fit (but was not too loose) it worked fine.

    I’ve had 100% reliability through about 800 rounds, not even a normal rimfire dud.

    It shoots a couple of inches low with the 36-grain CPHP Winchester load, but was accurate enough enough for training, and maybe emergency small-game getting.

  • Al

    The quality of welding for a commercial product looks amatuerish.

  • jdun1911


    Yes it will get dirty. Shooting cause guns to get dirty. You do not need to worry about the gas tube because whatever fouling will get blown out. I wouldn’t worry about the barrel a pass or two with bore snake will clean it up.

    Anyway I have not clean my main AR15 carbine for over 3k 5.56 rounds and God only knows how many more rounds I put with .22lr.

    About accuracy:

    The twist rate of the AR barrel and the inconsistency of .22lr is the main cause of negative accuracy and not “bouncing off the barrel” non-sense. The 1:7 twist isn’t great but will work. 1:9 is better and 1:16 is prefer. Most AR15 barrel are 1:7 or 1:9. Try getting 40gr or heavier bullet. That will improve your accuracy.

    Unless you buy match .22lr bullet don’t expect bulk .22lr rounds from Wal-Mart to give you to of the line accuracy. More like the bottom of the line accuracy. Accuracy wise it is more than enough for doing training 50 yards or below.

    Richard Allen,

    Yes you need to rezero when you use different type of make or model ammo. For example if you used 5.56 55gr Remington and you change to 5.56 55gr Winchester (different power and different amount of powder than Remington 5.56 55gr) than you have to rezero. If you use 55gr Remington and you change to 62gr Remington you need to rezero. In simplest term anytime you used different ammo you need to rezero.

    With that said if you’re experience enough you can compensated without the need to rezero.

    The reason you get the 5.56 conversion kit is for training with an AR15. I recommend it. The CMMG 22 Evolution is better than the normal kit because it allows you to do malfunction drills.

  • howlingcoyote

    After reading the comments above, all I’ve got to say is when will some company come out with a 22 Magnum conversion upper? It is a .224 caliber, not the .222 or .223 like a 22LR, plus jacketed bullets. I would like to see something like 20 or 25 round magazines for a 22 Magnum conversion unit.

  • howlingcoyote

    I forgot to add the 22 Hornet as a possible conversion upper or maybe even the 218 Bee. Now those would be interesting as low recoil and 25 round magazines!

  • drewogatory

    Holy cow folks. 5.56 x 45, .223 Rem and .223 Wylde are three DIFFERENT chamberings, with different dimensions. Only fire ammunition in the caliber your gun is chambered for. This is gun safety 101 here people. Wylde is .223 Rem with a longer leade, so you can safely fire either 5.56 x 45 OR .223 Remington, but accuracy will suffer compared to either.

    Do a little Wiki’ing and be safer!

    223 Remington versus 5.56 mm NATO

    These 5.56x45mm NATO cartridges are identical in appearance to .223 Remington. They are, however, not completely interchangeable.
    While the 5.56mm NATO and .223 Remington cartridges and chamberings are very similar, they are not identical.

    Military cases are generally made from thicker brass than commercial cases; this reduces the powder capacity (an important consideration for handloaders[9]), and the NATO specification allows a higher chamber pressure. NATO EPVAT test barrels made for 5.56mm NATO measure chamber pressure at the case mouth, as opposed to the location used by the United States civil standards organization SAAMI. The piezoelectric sensors or transducers NATO and SAAMI use to conduct the actual pressure measurements also differ. This difference in measurement method accounts for upwards of 137.9 megapascals (20,000 psi) difference in pressure measurements. This means the NATO EPVAT maximum service pressure of 430 megapascals (62,000 psi) for 5.56mm NATO, is reduced by SAAMI to 379.21 megapascals (55,000 psi) for .223 Remington.[10] In contrast to SAAMI, the other main civil standards organization C.I.P. defines the maximum service and proof test pressures of the .223 Remington cartridge equal to the 5.56mm NATO.

    The 5.56mm NATO chambering, known as a NATO or mil-spec chamber, has a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 Remington chambering, known as SAAMI chamber, is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber (Rock River Arms)[11] or the ArmaLite chamber, which are designed to handle both 5.56mm NATO and .223 Remington equally well. The dimensions and leade of the .223 Remington minimum C.I.P. chamber also differ from the 5.56mm NATO chamber specification.

    Using commercial .223 Remington cartridges in a 5.56mm NATO chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223 Remington chambered gun due to the longer leade.[12] Using 5.56mm NATO mil-spec cartridges (such as the M855) in a .223 Remington chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice.[13][14] Some commercial rifles marked as “.223 Remington” are in fact suited for 5.56mm NATO, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56mm NATO ammunition.[15]

    • Retired Armorer

      This “OMG! Mixing 5.56mm and .223 Rem!? We’re all going to die!” nonsense is getting awful damn tiresome.

      Yes, there are differences.

      Do they matter, in the real world? NO! Certainly not in the case of an AR-type rifle that will have its chamber cut to 5.56mmx45 dimensions.

      So spare us the hysterics. Raving about .223 Rem and 5.56mm differences isn’t a sign of being a “weapons expert,” it’s a sign of being a half-booksmart Wikipedia-trolling busybody.

      • AR Smith

        Actually, it does make a difference. You CANNOT shoot 556 out of a 223 barrel. It goes against both SAAMI regulations and chamber specifications. Unless you wanna halve the life of your barrell and jam up thr chamber often…

  • Justin

    I have one of these CMMG kits and I have to say the quality and accuracy was worse than I expected. The extractor arrived chipped and wouldn’t eject the brass. I replaced it and it has been fine.

    Accuracy in my LMT 1:7 upper is poor. 5 inch groups at 25 yards, 12 inch at 50 yards, and unsafe scatter at 100 yards.

    The Black dog mags work fine for me. They are a pain to load though:

    The issues aside, it is a blast to shoot and not worry about the cost.

    • TL

      I have to agree with Justin about shooting at 100 yds. After zeroing it in at 25 yards (1-2 inch groupings), I proceeded to the 100 yd range. Let me say that the bullets were flying all over the place. Some bullets would land short while others sailed over the target with the same scope setting. Needless to say, I was not able to zero in at 100 yds. I will try at 50 yds. the next time out. DISCLOSURE: I was using this on my Noveske 1:7 twist.

  • gt

    Guys for my two cents it seems that this conversion is a waste of hard earned dollars. Cinsidering the total lack of accuracy 9-10″ groups. Heck I can throw rocks more accurately. If you must have a conversion to .22 why not buy a real .22 or get a .22 upper.Pushing lead down range without accuracy is pointless.

  • Gunner

    With the prices of these conversion kits a little less than 200$, would it just be better to buy the Mossberg Tactical 22 Rifle? It’s just over 200$ much cheaper than the full cmmg 22 upper and it will have the right bore size for 22lr. Or are the ar clones not accurate as well?

    Also is it worth the extra money for the stainless conversion kits? It seems the people who review the 22 conversion kits the stainless steal have less malfunctions.

  • Andre

    Thanks for a great review

    Have a look at this:
    Seems like there are two areas on the “bad” magazine that needs filing…

  • richard Jones

    My Stag Arms 22 conversion shoots 2 inch center to center at 30 meters. Mags work flawlessly! 100 plus rounds no hang ups!

  • Retired Armorer

    The tight magazine problem is easily fixed. There are two small tabs on the rear of the magazine that need to be filed slightly to fit the magazine well. CMMG put them there to deal with the considerable variation and slop to be found in AR lowers from different manufacturers.

    A couple of minutes with a fine file and the tight magazine should drop freely in that lower.

  • Hey guys I have the cmmg SS converter and the smith and Wesson mags will work with the converter. The Smith and Wesson mags is cheaper in price

    • blake

      I have one of these and let me tell you they are awesome! just add a suppressor and you have one bad ass gun. Here is a video of one with a suppressor

  • I should have said the smith and Wesson 15-22 mags


  • blake

    great write up here is my video I did on my cmmg 22lr rifle with a gemtech suppressor attached

  • I had tight groupings at 30 yards with Remington 22lr ammo. The only jams or failures were “user error.” I did find it next to impossible to get 10 rounds in my Cali compliant magazines, so I settled for 9 rounds at a time. When I consider the dollars I’m saving, this conversion paid for itself my first day at the range. I was shooting a Bushmaster ORC and did have to shot very slightly above the target to hit it dead-on. Lots of fun for pennies on the dollar when compared to .223.

  • retrocon

    Good writeup, this helped me decide to buy.

    so in return, a recommendation

    Aguila SSS 60 gr subsonic through a 1:7 twist 16″ upper suppressed.

    1″ at 25 yards or better. No keyholling or baffle strikes as you get from this ammo through a .22 dedicated, 1:16 upper.

    nearly as hard hitting as a 60 gr subsonic .223.

    This, IMHO is where the CMMG shines.

    Did I mention quiet and reliable 😉

  • William Butler, MSG USA ret

    Just a recommendation, please read the instructions that came with the kit. It seems that the author may have overlooked this small detail. CMMG specifies certain brands of ammo as being acceptable with the kit. Second, you are ignoring the fact that 5.56 caliber barrels are over size compared to .22 rimfire barrels. Your attempt to get tighter groups is destined to fail, so save the ammo. Purchase a dedicated .22 upper unit if accuracy and tight groups are what floats your boat. This accessory is fun, but comes with inherent shortcomings. With cost increases and availability of .22 being what it is, mine gets used less these days. Oh yeah, the magazines come with a pretty good guarantee ( it’s in the instructions … hint, hint). Contact the manufacturer for assistance.

  • Freedom Fighter

    I have this .22 long rifle conversion kit and use it quite often in one of my AR15’s!