Scot’s Product Review: CMMG .22 LR Conversion for AR-15


We can have a lot of discussions about the good and bad points of the AR-15 and the .223 cartridge it is usually chambered for. Some think they are worthless junk, while others feel they are the cat’s meow. A lot of folks, myself included, are somewhere in between those two ends of the argument. I find the ergonomics to be quite good and very adaptable for left-handed shooters, like myself. You need to add an ambidextrous safety, and I think an ambi charging handle also helps. An ambi magazine release really rounds it out, but I can live without that part without much hassle. I do hate cleaning the bolt carrier group, which gets pretty cruddy from all the gas that enters the action. Other designs keep the gas out of the action and are much easier to clean.

One thing that we all have to agree on, though, is that the bloody things are everywhere. The military and most law enforcement agencies now issue them. With them so prevalent, I think shooters, and particularly preppers, should be familiar with them, even if they feel they are a subpar solution to any ballistic problem. You may find a chance to acquire one during a crisis, and it’s best to learn how now.

AR’s are fun to shoot. There isn’t much recoil to speak of, and they are light and handy, if one is sensible in how it is set. The muzzle blast is pretty noticeable, though, particularly with the 16-inch barreled carbines. Fancy muzzle brakes usually increase the blast effect, so I avoid them. AR’s tend to be fairly accurate, especially with match-grade ammunition. Mine will shoot less than one-inch groups with Federal 69 grain match loads and hold two to three inch ones with average training ammo.

All of this AR lead up is to get to something that can make the AR much more versatile and useful. While I’m not crazy about the .223 cartridge, there is another cartridge I am crazy about– the .22 Long Rifle (LR). The .22 is the preeminent cartridge for practice and for small game hunting. It is a blast to shoot, and you can do it all day and all night, thanks to the lack of recoil, noise, and muzzle blast. Since the .223 has bore diameter in common with the .22 LR, it is easy to convert an AR into a .22 LR in less than a minute by using a kit. such as the CMMG one. This slick $240 unit replaces the bolt carrier group in an AR with a chamber insert and a bolt that cycles and feeds .22 LR ammunition from the supplied magazine, which fits normally into the rifle.

My kit is an older model made of plain old carbon steel. They have newer ones made of stainless steel, which should make them even easier to care for.

Once you fit the kit into a rifle, you have a weapon that is much less expensive to shoot than the .223. While .22 ammunition has been hard to find, it is becoming more available. Even at the highest prices I saw (and refused to pay), .22 LR was still less expensive than .223, no matter if you reloaded it with components that were as hard to find as .22 LR ammo. Just as a reminder, now that things have eased, we need to replace what we used when there were problems. It might even be smart to add some extra for next time.

Besides being more economical to shoot, an AR converted to .22 LR is much quieter and has almost no muzzle blast. That makes it great for training new shooters, plus it means you can use it in places where a .223 makes too much noise. While the recoil from a .223 is minimal, the .22’s is non-existent, which adds to the appeal for young or new shooters. My son was somewhat intimidated by the AR when he began to outgrow his starter .22, but he fell in love with the AR conversion. It made it a lot easier for him to segue into shooting .223 a few months later. He was already familiar with the firearm, so all he had to do now was deal with the muzzle blast and a little more bounce. He was actually disappointed, I think, by lack of kick from the larger round.

Self-defense practice with the .22 LR isn’t the same as with .223, but it is close enough to be worthwhile. My split times between shots are almost the same.

There are some handling differences between the .22 LR and the .223 AR’s, mostly related to the fact the bolt catch doesn’t work properly. The bolt is held back by the empty magazine’s follower, but it doesn’t actuate the catch. The pressure of the action spring holds the magazine in the rifle so it won’t drop free the way most AR magazines will. You have to pull it out, which releases the bolt to go forward. The bolt stroke is perhaps half that of the .223, so when you pull the charging handle back, it stops early. That always leaves me feeling there was a problem when I chamber a round, even though all is well. It also means that the bolt can’t be pulled back enough to lock it open, so you can’t practice a bolt back reload using the bolt release. It also raises hackles at one range I shoot at that requires the bolt to be locked back and the magazine out while shooters are forward. I make sure to have a chamber flag when I go there.

I have seen an adapter that is supposed to operate the bolt catch, but it isn’t on the CMMG web page at this time. I have not tried it, and I note some complaints in the Amazon user reviews. Not all magazines work with it.

After using this to convert a .223 AR, I decided I wanted a dedicated upper receiver for .22 LR. The conversion works well, but the 1/7 twist barrels that work well with heavy bullets on the .223, isn’t optimal for accuracy with .22 LR. A 1/15 or 1/16 twist is most often recommended for rimfires.

CMMG also makes complete .22 uppers and rifles, but I like to build things for myself, so I bought one of their barrels, which go for about $160.00 these days.

I next picked up a flat top upper receiver from Brownells (I don’t even remember which brand it was) for about $100 along with a Colt Barrel nut assembly for $35.

The trickiest part was figuring out what to use to hold the handguard on the barrel with. AR’s usually have a front sight base which holds the handguard cap in place that, in turn, secures the handguard. I didn’t plan to use it with iron sights and I wanted something inexpensive and easy to put together in my garage. The front sight base is best pinned to the barrel and properly drilling holes for the pins is beyond my skillset. I found a gas block with Picatinny rails that clamps on the barrel with set screws for about $30, also from Brownells.

The end of the barrel is threaded and to give it a finished look, I put an A2 style flash hider on it. I don’t remember which one I got, but it was the cheapest one I could find from Brownells. It was under $10.

I also needed a handguard, so I got a Magpul one for another $25 or so.

Finally, I scrounged a charging handle from my leftover parts box, dug up a cheap scope and I was in business after some trivial assembly work.

I hate to admit this, but having a complete upper led, as part of mission creep, to building a lower for it so my son could have his own AR. So much for all the money I saved on ammo.

I have found the dedicated .22 LR barrel to be more accurate as a .22, on average, than the .223 barrel, but the .223 barrel has managed to come close to what I can get with the Long Rifle barrel. What I have noticed is that more varieties of ammunition shoot well in the dedicated barrel, while the .223 barrel only likes a couple of loads.

Another point in favor of the dedicated version is that rimfire ammo, especially the inexpensive blasting stuff with lead bullets, is often very dirty. I have seen debates about .22 LR fouling, and particularly leading, getting into the gas system on the .AR. I’m not convinced it is a big deal if one cleans after shooting and uses high quality ammo, but it can’t hurt to keep it out of your .223. A friend recently had some really rotten .22 ammo that heavily leaded a pistol to the point of inaccuracy and unreliability. I hate to think of that happening in my primary AR, so I made a point of using premium copper-plated ammunition when I was running it on my .223. Now that I have a dedicated .22, I’m not as careful and I have run some rotgut bargain ammo through it. While I paid for it when I cleaned the barrel, I did get some cheap practice without any risks to a defensive weapon.

As far as accuracy, it is pretty close to my Ruger 10/22, though it is more selective about what it likes. My best groups with the Ruger run about one inch at 50 yards, while the best ones with the CMMG have been 1.5 inches. I have had the Ruger for years and have gotten to try a lot more ammo with it than the CMMG, so I suspect there may be some better groups in the future with the CMMG as I do more testing.

It is common for a .22 to have particular tastes in ammo. None of my .22’s agree on what good ammo is, much to my frustration. I have had to lay in a separate supply for each one of them– handgun as well as rifle– as if life isn’t complex enough. I don’t worry so much for practice, but I want the most accurate stuff I can get for hunting or pest control.

CMMG says they find that the Federal and CCI 36 grain loads usually do well, and that mirrors my results. The most accurate round in mine so far has been CCI Mini Mag hollow points. Annoyingly, it doesn’t like the Mini Mag round nose that my Ruger likes. I’ve also seen folks tout the CCI Subsonic loads with these setups.

I should point out that I am using the same model scopes on both rifles. I got them on sale, and there was a reason they were on close out– they were cheap; I would never have paid the original price for them. One of these days, I intend to put better scopes on both, and I suspect that will help accuracy a bit.

The triggers on the Ruger and the lower receiver I used with the CMMG upper are pretty equal. The Ruger is a bit heavier and the AR is creepier. The shooter, in both cases, is pretty lame. A better marksman would get nicer groups.

Reliability has been excellent. It has run standard and high velocity ammunition without qualms. It will not cycle the CCI Quiet ammo, but none of my semi-autos will. CB caps, of course, won’t cycle it, either. It actually has been a tiny bit more reliable than my Ruger, but you can count on either rifle to work. Cleaning has always solved any issues.

I’ve seen a number of AR look-alike .22 rifles, but most of them just have the appearance and not the innards of an AR. They are usually lighter, not as sturdy, and don’t truly replicate the feel of an AR. Some of them are decent firearms, but I just don’t think they provide the same quality training as a real AR converted to .22, either with a complete upper or just the conversion kit.

I am very happy with my CMMG conversion and have no regrets about buying it. I am also very happy with the upper receiver I built with their barrel. It is reliable and accurate enough to use for hunting. I am thrilled to have it for practice as well as starting off new shooters. It is a good piece of kit and worth the money. I have more in it that one might put into a 10-22, but a 10-22 will never come close to simulating an AR. It’s nice to have both, but if you could only have one, the conversion makes a lot of sense, if you run AR’s.

Product Update DRD Tactical AR-15

Speaking of AR’s, I recently reviewed the DRD Tactical take down iteration of the AR Besides the allure of having an easy to pack rifle, you can easily swap barrels giving you one gun that shoots more than one cartridge. The one I am testing came with .223 and .300 AAC Blackout barrels, and I finally managed to scrounge up some .300 ammo and make some time for a range trip to see how it works.

The bottom-line is that it works well. There is a bit more push to the shoulder than a .223 but nothing to fret over. The muzzle blast is easier to bear than the .223, which makes it more pleasant to be around, particularly in an indoor range where I did some of the shooting.

Due to recent increases in .22 rimfire ammo costs and ammo shortages, I only have about 100 rounds through it so far, but it has been 100% reliable. Accuracy is fine with groups running about 1.5 inches at 100 yards using a Leupold VX-III 1.5-5x scope set at 5x. I suspect careful hand-loading might get better groups, and there might be a better factory load than any of the three I have tried. I should also again remind everyone that I’m not the best shot and a better shooter will likely shave some off of these groups.

I like the rifle and find the cartridge intriguing. It hits harder than a .223, but it starts running out of steam pretty quickly. My thought is that it is at its best under 150 yards. It is by no means a .308. Bullet selection appears very important. Most bullets for .30 caliber are designed for more powerful cartridges and won’t expand at .300 AAC velocities. There are bullets that will work and they should be selected. Many hunters have reported good results using it on medium game within the limitations of the cartridge. I hope to match them if my plans to try it on hogs next month pan out. – SurvivalBlog Field Gear Editor, Scot Frank Erie

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