One of my New Year’s resolutions is to reject, at least temporarily, internet hearsay. You know what Abraham Lincoln said about the internet, right? “Four score of lies, myths, exaggerations, and urban legends.” That’s a long way of saying lots of folks read something and then pass it on as the gospel truth.

Knowing that I can be a victim of internet “rumorroids,” I’ve decided to do something about it. When I hear something that sounds like an established claim, but with nothing to back it up, I just might test its validity myself.

One claim that’s been passed around for years is that .22 LR conversions for AR rifles aren’t worth the trouble because they aren’t accurate, rarely function, and have been known to cause massive outbreaks of shingles. So to start my 2015 resolutions, I decided to test one of those kits for myself, just to see.

I ordered a 22AR Conversion Bravo kit from CMMG, which is $230. The Bravo kit is as basic as it gets. It consists of a stainless steel bolt replacement and a single 25-round magazine. If you live in a rights-challenged state, you can get a Bravo kit with a 10-round magazine.

The basic idea of this conversion kit is simple: you only replace the bolt and magazine. The front of the conversion bolt features a “chamber” that’s a replica of a .223/5.56x45mm cartridge, so that fits in your existing chamber and barrel. The .22 LR cartridge feeds into the pseudo-chamber on the bolt replacement kit and fires the .22 LR projectile out of the conversion kit chamber and into your normal barrel. The theory is that a standard .223 barrel is close enough in diameter for things to work out. Make sense?

To find out how this worked, I brought it to the range along with two AR-type rifles: a Smith & Wesson M&P15 VTAC and a Smith & Wesson M&P Optics Ready (OR) model. The VTAC has a 1:7 twist barrel and the OR has a 1:8. We’ll talk more about that later.

I tried the 22AR Conversion in two different Smith & Wesson ARs.
I tried the 22AR Conversion in two different Smith & Wesson ARs.

Since I was in myth-testing mode, I played dumb, which wasn’t all that hard, and tore open the packaging at my shooting bench. I figured instructions were optional since there were only two parts, so I opened up my upper receiver, removed the bolt, and dropped the conversion bolt into place. After switching to the CMMG .22 LR magazine, I was ready to go. The whole operation, including not reading any instructions, took me about a minute. Most of that time involved tearing open the packaging.

Did it function reliably?

Right off the bat, I experienced quite a few jams and malfunctions. Then it occurred to me that I hadn’t provided any lubrication to the new bolt. That’s what you get for diving right in without stopping to think. As a result of all this reflection, I remembered that the new bolt felt completely dry when I removed it. I remedied the situation by squirting a few gobs of OTIS Technology CLP into the ejection port. Following proper lubrication instructions is for sissies.

Installation is easy—just drop the replacement bolt in.
Installation is easy—just drop the replacement bolt in.

Voila! Once I actually added some oil, things worked like a champ. I shot about a dozen different types of .22 LR from both rifles with the conversion installed and experienced zero malfunctions. One thing that surprised me was that standard-velocity ammo worked as well as high-velocity rounds. I wasn’t sure if the standard loads would generate enough pressure to make things work, but they did.

What about accuracy?

Before I did accuracy testing, I pondered some geometry stuff.

.22 LR cartridges actually have different bullet diameters depending on the load. Many of the target and general purpose 40-grain lead bullets are closer to .224 inches in diameter than .223, which is “normal” for .22s. This led me to believe that I might be able to get some decent accuracy out of the conversion kit, since the bullet diameter could be the same or very close to that of a standard .223 Remington projectile, which also (usually) measures .224 inches diameter.

Accuracy was surprisingly good—if you pick the right ammo.
Accuracy was surprisingly good—if you pick the right ammo.

In addition to the diameter variance of different .22 LR cartridges, I also assumed that the Smith & Wesson M&P15 OR would be more accurate due to its lower twist rate. A “normal” .22 LR rifle like a Ruger 10/22 has a twist rate of 1:16, which is quite a difference from the 1:7 and 1:8 or the two test rifles. I figured the twist rate issue would be the cause of any serious accuracy problems.

Here’s what I found.

CMMG 22AR Conversion Accuracy

As you can see, my theory was correct—the 1:8 twist rate AR shot appreciably better than the 1:7 version. I also checked for point of impact variance. Yes, it was a little off from that of .223 rounds at a 50-yard range, but only by about an inch. For inexpensive practice with your “real” rifle, that’s a pretty good tradeoff.

I have to say I was pleasantly surprised by these results. Yes, you can buy a dedicated .22 LR rifle that will shoot tighter groups, but remember, we’re talking about a bolt conversion kit here. The chamber and barrel are in separate pieces! Considering that I can drop this in, and shoot .22 LR ammo, I think it’s a heck of a deal. .22 LR is more expensive than it used to be, but it’s still $0.08 per round give or take. That’s a lot less than the $0.25 per round for .223/5.56mm ammo. Plink away!

Tom McHale is the author of the Insanely Practical Guides book series that guides new and experienced shooters alike in a fun, approachable, and practical way. His books are available in print and eBook format on Amazon.

Images by Tom McHale

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8 thoughts on “.22 LR AR Conversion Kits: Are They Worth It?

  1. Good article.

    If I may ask though…Since one of the stated purposes here was to test the myth that these conversion kits “aren’t accurate”, the article needs a baseline for your accuracy.

    I like that you dropped this into two different rifles, but the provided data only shows how grouping differs between the two converted rifles, not how a) the converted AR15s differ from a dedicated .22 AR style rifle or b) how your grouping differs on those two rifles converted vs. unconverted. (i.e. you may always have a tighter grouping with the M&M 15 OR and the difference above has nothing to do with the conversion).

    Can you throw those charts into the mix? Thanks.

    1. Sure, both of the test rifles will shoot inside of a one-inch diameter at 50 yards with half-decent .223 ammo. The test here was not intended to be a scientific analysis of the .22LR versus native cartridges, but rather an “is it good enough” measure. A good .22LR dedicated rifle will shoot into less than .5 inches at 50 yards with quality ammo, but that’s not the intent of a conversion kit like this. This type of solution is intended to provide a quick, easy, and less expensive option for your centerfire rifle, so to me, the question of “is it good enough” can be answered by your tolerance for group size considering what this solution is designed for. Since it shoots into an inch and a half, with no big change in short range point of impact, it’s plenty good for running drills etc at ⅓ the cost of using .223 5.56mm ammo.

      1. Gee the MP-15 has about a 7 to10 lb. pull triggr, had you used an (Ammodump NPC 15) you would have had a 3lb pull standard trgger making things much more accurate,

      2. True, that would have helped, although the S&W VTAC has a Geissele match trigger. So the “accuracy” is more a result of faster twist rate than a .22 expects in this case I think. In either case, it was plenty good for the purpose, and I was pleasantly surprised that it shot so well.

      3. Thank you for providing information about these conversions. A few years ago I chose to purchase a complete .22LR upper from DPMS. With its 1-16 barrel, the DPMS is capable of sub-MOA accuracy with decent ammo. Being able to practice at a reduced cost is certainly a bonus. I’d like to mention that my Marvel .22 conversion for the 1911 prints 0.314″ ten-shot groups at 50 yards using Eley Ten-X.

  2. I’ve had a Ciener .22LR conversion kit (looks exactly like the one
    pictured but is phosphate coated and the 30 rd. mag is skinny) for many
    years. It works just fine in my Colt A2.

    Some brands of ammo
    don’t eject reliably so I keep a 6″ aluminum rod in the kit to poke
    them out when it happens.

    Accuracy is reasonable in my 1:7 barrel but of course the lower velocity .22LR rounds hit way low. I’ve
    found that if you jack the AR sights up to the max the LR hits on target
    at 50 yds.

    When .22 rimfire was cheap and plentiful it was fun spraying
    the target John Wayne style.

  3. I have the .22 conversion for my AR 15 and it works great. I have a 1 in 14 M-16 barrel and the accuracy is great at 50 yards. There doesn’t seem to be any difference between standard velocity and hyper velocity, lead nose and copper nose. The only bad part is that they recommend after about 300 rounds you run a couple of mags of .223 through it to clean out the aluminum gas tube. Other than that, it is a great alternative to using expensive ammo to keep your shooting skills sharp. The only question I have is, can it safely fire 22 LR magnum rounds? That might put the .22 conversion in a whole new category Target practice at 100 yards?.

  4. I have to correct my previous post. It is a 1 in 16 twist. I should have proof read it before I posted it. It is also a standard 20 inch barrel.

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