CMMG AR-15 .22 LR Conversion Kit Review

by Derrick James

Today’s post builds off my previous AR-15 A2 survival rifle post. If own an AR-15 and you accept the notion that practice makes perfect (who wouldn’t), you’re then faced with the daunting financial task of buying enough .223 ammunition to become proficient with the rifle.

Enter the CMMG .22lr conversion kit for the AR-15. Lucky Gunner , a seller of bulk ammo, ammo cans, and more, sent me a conversion kit  to review.

cmmg .22lr ar-15 conversion kit

But before we get too far, let’s first consider the why?

Why Buy a .22 LR Conversion Kit?

Obviously – to save money! You spend money to save money. If I stroll over to Optics Planet for some ammo to do the math, this is what I see:

  • .22lr ammo – 12 cents per round for high velocity (more on that in a bit)
  • 5.56 ammo – 57 cents per round for target practice quality (when available)
  • CMMG .22 LR conversion kit – $235.00

There is a 45 cent per-bullet difference in price between the 5.56 and the .22.

$235 (the cost of the kit) divided by 45 cents = 587.5. You will recoup the cost of this conversion kit in 587.5 rounds. How many rounds do you shoot if you go to the range? The conversion kit pays for itself in no time. Then it’s all savings.

Are There Other Reasons to Buy a Conversion Kit?

Yes, there. I’m glad you asked!

  • If someone is new to shooting, the .22 is easy and fun.
  • You’ll shoot more, because every time you open the box you won’t be thinking “ugh, that’s X dollars.”
  • You’ll become a better shot, because you’ll shoot more.
  • Did I mention the .22 is easy and fun?

Here are all the items unboxed:

cmmg conversion instructions

There are instructions, a magazine, and the bolt assembly. At the bottom of the long sheet is a diagram of the style hammer an AR-15 should have to properly function with this conversion kit.

Rounded hammer = good.
Notched hammer = bad.

There were actually two of us field testing this. Conveniently, we had two different hammers:

ar-15 hammer type

The rounded hammer is supposed to have fewer jamming issues with the conversion kit.

Other important points to note in the instructions:

  • high velocity ammunition is recommended
  • expect minor jamming issues in the beginning as the bolt assembly breaks in
  • trim areas of the magazine so that it properly fits in the magazine well, right here:
filing magazine

The .22 LR magazine functions fine with the AR’s magazine catch assembly. Here is a photo comparison of the parts:

.22 conversion magazines

You simply slide one bolt assembly out and slide the other one in. The ammunition used:

.22lr ammo for AR-15

I bought new high velocity rounds (on the left) for this review. We put lubricant on the new bolt assembly and fired away. We used both my notched hammer and his rounded hammer.

I had no problems with my hammer in the first magazine of rounds. His, with the rounded hammer, jammed a few times and fired 2-3 shells with just one trigger pull. That was the first few magazines’ worth of ammo. The conversion kit went back and forth between rifles and we both had jams:

casing jam
.22lr jammed

Remember: these early jams/issues are part of the breaking in process. By the time we fired all of the .22 rounds pictured earlier, if we were using the high velocity stuff, we had no problems. No jamming and only one shot per trigger pull. High velocity rounds + initial break in period = fully functioning conversion kit. While I used my notched hammer for this review and had it work fine, the directions suggest rounded for a reason.

My only problem with the conversion kit is that the AR barrel has a twist rate for the 5.56, not for the .22. A .22 should have a 1/15 barrel twist, not 1/7 or 1/9. This impacts accuracy. How much and is it enough to matter? Because it was so cold, getting late and the snow was up to my waist – literally – we didn’t test that. I know we were both hitting the target:

conversion kit at range

The conversion kit is slick, fun and saves money. If money is no object, you might prefer a designated upper in .22 caliber for appropriate twist rate; but that’s more expensive and pushes the time it takes to make your money back through savings on ammo.

A Final Thought and Alternative

If the conversion kit costs almost $250, you’re almost half way to an entirely dedicated .22 AR-15. Making that plunge would give you an entirely completed rifle designed specifically for the .22 LR round, from barrel rifling to trigger pull.

So you have to ask yourself – is an M&P 15-22 worth buying?

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18 comments

bob sykes March 10, 2011 - 2:04 pm

Do you know which manufacturers use notched or rounded hammers?

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Spook45 March 10, 2011 - 2:14 pm

Im wierd about things like this. I would not want to send soft lead 22s down my ar barrel. I have not experianced it first hand but I have read several articles about this and a lot of folks say that over a prolonged period of time that the lead fowling caused problems down the road. IDK myself, but I were going to do this, I think I would spend just a little more and buy a dedicated 22 upper and be done with it. They dont cost that much and since it is sort of the new thing going they have gotten pretty popular and the prices on them have come down a little.
I concidered this option but instead I just went and bought a brand new ruger 10/22 to go with my ruger 22/45 and called it a day. Just my 2cents. to each thier own.

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lumberjok March 10, 2011 - 8:30 pm

I agree spook, why not pony up a few more bucks and march down to Walmart and pick up a 10/22. You will wind up with an ultra reliable light weight rifle with a barrell that has the proper twist rate for .22 long rifle. From there the sky’s the limit, there are literally thousands of add-on parts if you choose to customize.
I have tried a half dozen hi capacity mags, some flat out don’t work and some kinda sorta work. The only bomb proof mag is the standard 10 round rotary Ruger mag. You can then buy an Alangator tri-mag device which allows you to clump three mags together. With practice you can rotate a new mag into place in no time.
Ammo wise browse over to Midway USA and pick up a couple of bricks of Aguila Super Max (30 grain hollow points screechingly fast at 1740 fps) Zero at 50 yds and you’re still dead on at 100.
Devasting on coyotes.
If you want to trick it out, start with a Tapco T-6 stock and voila you have a black gun.
Beware, the 10/22 is addictive. I’m ashamed to admit how much I have sunk into mine. Custom trigger, stock, barrel, acog sight. But then again insanity does run in my family.

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Spook45 March 11, 2011 - 1:09 am

I use the eagle mags. They are cheap and they run. They dont last forever, but you get your moneys worth for the price. They are so cheap I got like 12 of them. They are only 9.99 from centerfire systems and if you catch them on sale you can get them for arou 7.00ea. I have one ramline with the steel feed lips and it is killer but its also $25 a pop. I will stick with the eagle mags.

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DaveNV/AZ March 10, 2011 - 11:19 pm

Spook45, I remember years ago when I was in the USAF that the range people didn”t like taking care of or cleaning the adapted weapons. We wold practice with or own issue weapons and then for longer range time we would use the adapted range rifles. They did this so that Our duty weapons and our war weapons were sighted in to the round we used. We then used the adapted rifles to get range time with the weapons. Back then it was a waste of time and I believe it would still use up the barrel before its time because your still putting rounds through it.

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Geoff Ross March 10, 2011 - 2:16 pm

I use a Ciener kit similar to the one shown with Black Dog 27 rd mags. Use Federal bulk 22 ammo that is PLATED! Do not use unplated lead as it will lead up the rifling and foul the bolt. Never found the need to use high velocity ammo. Do get an occasional jam mostly related to the ammo, but jams are infrequent.
The bolt needs a thorough cleaning after each shooting session.
I shoot an old Bushmaster Post Ban upper with 20″ bbl. Found that shorter barrels jam more.
YMMV. These kits are great stress busters.

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3rdMan March 10, 2011 - 4:05 pm

THe rounded hammer is an M16 hammer. The hammer used in AR15 is based on ATF regulation. The reason for the different hammer in an AR 15 i s for the following reason. It is designed to damage any M16 firing pins that is used in AR15 rifle without replacing the hammer as well.
Just some of the little design changes that ATF requires to hamper illeagal conversions.

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Hokie March 10, 2011 - 5:54 pm

To build on this, without a carrier designed to utilize the notch then it’d be safe to call the “notch” unnecessary, but not at all detrimental to the operation of the firearm.
On the other hand the rounded hammer would not allow the original M16 design feature to work if used with an unshrouded type carrier. This is stems into the political stuff 3rdMan is referring to…and it was just that – political.
Therefore, if you have an unshouded carrier and would like to utilize the original M16 design intent then a notched hammer is the way to go. Clearly and irrefutably true.
If not then personal preference is the deciding factor. Rounded hammers work more “comprehensively” in the AR platform. For the vast majority of non-NFA owners….that’s all you’ll ever need.
Either hammer will work flawlessly….but it’ll work “more betterer” with a rounded hammer.
Clear as mud! I own both, and never had a problem with either hammer amid the multiple thousands of rounds I’ve shot over the years through my AR’s. I think the notched vs rounded hammer debates are limited to the 22lr conversion.

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russell120 March 10, 2011 - 4:32 pm

I have found the CCI mini mag works well in my semi-auto .22lr.
I bought the 22lr automatic pistol as a practice pistol. If you use underpowered ammunition, it is excellent practice for dealing with incomplete cycling of rounds. And of course 22lr will always give you a little practice on misfires.
Beyond that though, even at the level of pistol practice, the lack or recoil really limits the practice practicality.
It’s fun. A relatively heavy (zero recoil).22lr revolver may be the only way to get some very nervous types out to the range. But I just don’t buy the 22lr practice blackgun concept.
Obviously a lot of people disagree with me as you see many examples of them at the gun shows.

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sanityjones March 10, 2011 - 5:51 pm

I do not see this as a practical conversion. I bought and shoot my AR15 to get good at shooting my AR15. If I wanted to practice shooting my .22 I’d shoot my .22.

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BrianT March 10, 2011 - 7:41 pm

Then there is the scary possibility that the SHTF while you have your rifle in 22 mode, and wake up to a mob of zombies banging on your door who just don’t seem to want to leave you alone from 1 or 2 22 rounds to the forehead.
Luckily in that situation the AR-15 can also serve as a club.
Shooting 22’s out of an AR-15 is a cool thing to do, and plinking targets with it may make you feel more awesome than shooting a small 22 rifle. However in my opinion, recoil, balistics, trajectory, weight all come into play when practicing a rifle. I have a S&W 357 mag, and a 22 revolver. They both look exactly the same, but firing them is worlds different.

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Prepared N.D. March 10, 2011 - 8:40 pm

I think this would prove to be more practical if you had a close quarters range set up and wanted to work on your speed. I wouldn’t want to blow through .223 firing at multiple targets within 50 feet for example.

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NoMEPreppy March 11, 2011 - 12:34 am

IMHO I think you would be scads better off to buy a separate .22 LR rifle. It’ costs about the same, if not less, and then you have 2 rifles and never have to worry about changing things out. I think that the conversion kit is just a bauble, not really worth the money. Heck, if you want a 22 that looks like an AR, they make those too.

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sanityjones March 11, 2011 - 1:13 am

There is also a golf ball launcher attachment for the AR, just in case you’re attacked by a mob of pimple faced caddies………….I’m still not sure how the AR15 fits in the golf bag, LOL.

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Spook45 March 11, 2011 - 1:15 am

Most of the AR 22 conversions cost around $200 +/-. A dedicated 22 ar only cost around four, I would rather just buy the dedicated upper. I probly never will,I like my 22 and I like my ARs the way they are. I do have a 22/45 pistol that is nearly identical to my 1911. I would like a chiappa 1911 22 but Im NOT buyin another one!

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Tdoro89 May 24, 2011 - 2:26 pm

It seems that you guys are failing to realize that the whole point of this conversion kit is to get better at handling and shooting your AR-15, not your .22 LR. You may not get to practice shooting with exactly the same conditions as a standar AR (ballistics of a .22 being different than a .223) but its better than not shooting the rifle at all. Going out and buying a 10/22 and practicing with it is not going to make you a better shot with your AR.

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Don Peck November 28, 2018 - 7:06 am

Tdoro89…you hit the nail on the head…the conversion kit has a couple of purposes…1) to save you money while practicing with your AR-15 rifle…2) gaining further familiarity with your particular rifle so when you pick it up you you are thoroughly comfortable with it. There’s “nothing better” than grabbing your AR and fealing 100 percent comfortable with it…day or night…the old adage is right on…practice makes perfect. Period.

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