Author Topic: CMMG Evolution .22lr conversion kits for AR15 rifles, a buyer's guide & review.  (Read 12340 times)

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Offline PetrifiedWood

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Just wanted to make mention of these little .22 conversions for AR15 rifles. I have been researching them heavily the past few days and wanted to share the results of my findings. I had to look all over online to find this information, and I thought it would help someone else to have it all in one place.

With .223 and 5.56 ammo prices exceeding a dollar for every two rounds fired, it's not practical for most people to shoot these calibers regularly because of the expense. Gasoline prices are bad, ammo prices are atrocious! A conversion kit allowing you to shoot relatively inexpensive .22 ammo that comes in under a nickel a shot is a lot more attractive option that will allow most people to get out and enjoy shooting their rifles a lot more often for the same price.

I was initially reluctant to consider these conversion kits because the AR15 rifle is a gas operated system, and I was concerned that the dirty, non jacketed .22lr ammo would clog the gas port and foul the action. Everything I've read indicates that all a person need do is shoot a .223 round or two through the gun to blast away any fouling after shooting a bunch of .22lr. Also, several thousand rounds of .223 can put significant wear on a barrel, even the chrome lined ones. You can shoot the .22 through the gun almost indefinitely without causing significant barrel wear.

So with that said, here's a link with a little history on the .22 conversion kits.

http://combatrifle.net/22conversion_history.htm

There are a lot of these Ciener kits in circulation nowadays. I have heard good things about them, but I've also heard their customer service is non-existent at best, and downright ugly at worst. I haven't had any experience with their products or service personally so I'm just passing on what I have heard. But it was enough to deter me from buying that particular brand.

Fortunately, there is another company making conversions, CMMG, that is very highly regarded. Over the past few days I've been researching these conversion kits and finally decided on one to purchase. The CMMG kits come in several different varieties with a range of different features. The first kits called "ARC" kits, come with either a basic, parkerized bolt, or a stainless bolt, depending on model. The ARC kits have been discontinued, but there are plenty of them available at great discounts from many retailers.

The latest CMMG 22 conversions are called "Evolution", and they have some features that the previous ARC kits did not. Their base model still comes parkerized. But the newer stainless Evolution kits come in a few different configurations, each of which can be upgraded to have all the features of their top of the line "India" kit.

I have read reviews that say the basic parkerized version needs a bit of a break-in period to run well. Based on the features it has (or doesn't have), I think I'd chose one of the older discontinued stainless ARC kits over the Evolution base model in parkerized finish. The newer stainless Evolution kits have some great features. They are compatible with CMMG's new second generation magazines that have "bolt hold open" followers. These magazines, used with a bolt hold open adapter, will lock the bolt open on an empty magazine just as though you were shooting centerfire ammo in the rifle.

Another available option with the Evolution bolt kits is an adapter that allows you to use your forward assist. This is probably never going to be necessary with a .22 conversion kit, but it does make the functioning of the rifle more realistic. That can be valuable for training purposes.

I mentioned the bolt hold open adapter. This is a device that requires a bit of minor fitting that can be done by the user. It sandwiches between the upper and lower receivers, and operates the rifle's bolt catch when a compatible magazine's follower activates it.

Also available with these kits is a special charging handle. The regular charging handle will work, but in the event of a jam, ammo can become caught in the deep channel of the stock charging handle, requiring the bolt kit to be removed from the rifle to clear the jam. The anti-jam charging handle is made shallower to help prevent this from happening, so you can clear the jam without taking the rifle apart.

The CMMG Evolution kits also have improved live round extraction. These "Atchison" style conversion kits are blowback operated. Older versions rely on this blowback to extract fired cases. However .22lr is notoriously inconsistent ammunition, and the occasional misfire is inevitable. Older conversion kits do not reliably extract these rounds without the benefit of the blowback action. The CMMG Evolution kits (not their older, discontinued ARC kits) are designed to extract live rounds.

Also worth noting, the newer kits have a go-no go gauge built into the chamber adapter to allow the user to check if the hit's rails are out of adjustment. the newer kits include a mainspring guide rod that has a slot for patches and can be used as a cleaning rod.

Additionally, they make a special brass locking lug that mounts to the chamber adapter. This allow you to lock the conversion kit into the barrel's chamber extension using the existing bolt locking lugs. This can help improve accuracy vs. kits that don't have this feature. This can only be used with the stainless Evolution kits. All other kits are not compatible with this feature.

As for accuracy with any of these kits, much of it depends on the rifling twist rate. AR15 barrels are designed to stabilize heavier .223 and 5.56 bullets. The twist rates in these barrels are more aggressive than those in .22lr barrels. Most .22 lr rifles have a 1:16" twist. AR15 barrels typically come in 1:7", 1:9", and 1:12".

The 1:7" barrels are not well suited to conversion kit use with anything but the heaviest .22lr ammo. The 1:9" twist will work with the 36 grain federal bulk ammo that CMMG recommends for good functioning. Obviously a 1:12" barrel would be better for the .22 ammo but most commercial rifles will have the 1:9" "compromise" twist in them for best performance with a wide range of ammo. One of the guys that shoots in the matches I go to uses a conversion kit with bulk pack ammo and he has no trouble hitting any of the targets on the first shoot, so for practical accuracy they are sufficient. I wouldn't want to compete against a quality purpose-built .22 rifle in a bench rest match with it, but for these practical shooting patches and casual plinking they appear to be accurate enough.

Magazines are available from several sources. CMMG has two versions. The older grey plastic magazines, and their newer, modular second generation Evolution mags. the newer ones are out of stock and back-ordered everywhere. they are a big improvement over the older magazines so they will be worth the wait, but as of the date of this writing the grey magazines are readily available, and function just fine. Their are other manufacturers of magazines that will work with the kits. S&W, Black Dog Machine, Ciener, and Pro Mag will all work, but whether or not they will hold open the bolt, or operate the BHOA is anyone's guess. My recommendation based on my research is to buy the CMMG mags to get started, then get some of the upgraded Evolution mags when they are in stock.

The grey CMMG magazines typically come with a green follower. This follower will hold the bolt open, but it does not activate the rifle's bolt catch. So when the magazine is removed, the bolt will close, requiring you to use the charging handle to load the rifle after a magazine change. "What's the point?" you might ask. Well, like many older .22 bolt designs, these conversions kits must not be dry fired!  By locking the bolt open after the magazine runs dry, the kit is protected from dry fire damage.

There are some upgrade followers for the grey plastic magazines that come with stiffer springs, and are designed to work with the CMMG bolt hold open adapter device to operate the rifle's bolt catch. The newer Evolution magazines will operate the BHOA without modification.

CMMG also makes a modified dust cover that comes with a shell deflector. It comes standard on their dedicated .22 upper receiver, but they don't include them in any of the kits. Most folks who get the conversions don't run the shell deflector dust covers, so they probably don't make that big a difference. I've seen videos of people firing the kits without the deflector dust covers and the shells shoot right out the side of the rifle so no big deal. The deflector cover throws them forward.

I have a couple of these conversion kits on order, one of the discontinued ARC kits, and one of the current Evolution "India" kits with all the bells and whistles. Midway USA has the newer CMMG Evolution kits, and I ordered the ARC kit form Amazon. When they arrive I'll get them installed and put some rounds downrange and give you a firsthand account of how they work for me.

I made this decision after fiddling with the Nordic Components kit for my Ruger 10/22 rifle. It works, but I'd have to spend so much more to make it "right". By converting an existing AR15, I'll be able to practice with a real rifle, instead of a cobbled together mimic. And it literally takes seconds to convert from .22lr to .223 with these kits, though changing calibers will require zeroing the rifle again. By getting a conversion instead of a dedicated rifle, it will allow me to use the same optics, mounts, furniture and other upgrades with two different calibers... another "hidden" cost savings. The temptation is to get a second dedicated .22 rifle and then put cheaper parts on it to save money. But this has proven to be a net expense, rather than a savings, as the cheaper parts do not work nearly as well as the better quality optics, mounts and hardware I have on my centerfire rifle. Another advantage of a conversion vs the Nordic Components kit, or the Ruger SR-22 rifle is the bore axis is lower on these rifles than it is on a converted AR15, meaning the scope height above bore is greater on those rifles than the already high AR15 platform. Not bashing on the Nordic or Ruger rifles, they are very high quality and if you have the money to spend making them as identical to your centerfire rifle as possible, they can be really nice, and have the potential to be more accurate than a conversion kit. But one serious optic is expensive enough, let alone one for each rifle.

I hope this helps answer some  of the questions you might have when considering a .22lr upgrade for your AR15 rifle. I know sub caliber conversions are popular with single shot shotguns for increasing their versatility. While AR15 rifles are perhaps not as traditional looking as single shot shotguns, they are definitely fun rifles to shoot, and being able to shoot them for much, much cheaper is going to be even more fun!
« Last Edit: October 14, 2012, 06:43:25 PM by PetrifiedWood »

Offline Moe M.

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  PW,  congrats on your decision,  i have some experience with conversion units on my 1911's and was never disappointed,  I've a friend who has conversion units on his AR's and has had little in the way of problems.
  I went the other option with the S&W MP AR-15 - 22,  so far I'm really happy with my choice.
 
  The one thing you didn't mention in your post was prices,  I'm curious as to the final cost of the different kits.
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Offline PetrifiedWood

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Thanks Moe!

The prices vary from about $150 or so for the older ARC kits in parkerized finish with one 1st generation magazine, to the top of the line Evolution "India" kit that comes in stainless steel with live round extraction, go-no go gauge, brass locking lug collar, bolt hold open adapter, cleaning rod/spring guide, Magazine loader, a GenII modular magazine etc. for around $330 or so.

Offline Moe M.

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Thanks Moe!

The prices vary from about $150 or so for the older ARC kits in parkerized finish with one 1st generation magazine, to the top of the line Evolution "India" kit that comes in stainless steel with live round extraction, go-no go gauge, brass locking lug collar, bolt hold open adapter, cleaning rod/spring guide, Magazine loader, a GenII modular magazine etc. for around $330 or so.

  That's a hundred bucks less than the cost of my dedicated AR-22RF,  something to consider,  but I'm still happy with my purchase,  a lot has been said pro and con about the AR-15 platform,  some only see a black evil gun,  others see a versatile, handy, and powerful light weight rifle/carbine that suits many hunting as well as defensive uses.
  I'm of the second group,  so it just makes sense to me to have an AR that handles .22RF ammo for fun, small game, and practice which transfers directly to the center fire model.
 Mine has paid for itself just in the savings on the cost of the difference in ammo,  and in wear on my center fire AR's,  so for those who own a AR-15 center fire,  whether they choose a conversion unit or dedicated .22 RF AR rifle,  they won't be sorry. 
In youth we learn,   with age we understand.

Offline PetrifiedWood

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I'm sure looking forward to getting out to the range to give this kit a try. It showed up today and I am hoping for some time to put it in a rifle and see how it functions with action proving rounds. The mags are designed to be fitted to the receiver so that will be a project as well.

Offline PetrifiedWood

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Re: CMMG Evolution .22lr conversion kits for AR15 rifles, UPDATE!
« Reply #5 on: June 03, 2012, 03:28:41 PM »
Figured it was time for an update. I received the kit a couple of weeks ago. The one I ordered appeared to be an older, ARC kit, but to my surprise a newer "Evolution Bravo" kit arrived. It required a slight bit of fitting to make it instal easily. It came with the first generation grey magazines. These magazines also require a bit of fitting to make them seat in your magazine well and drop free.

I had one malfunction out of about 300 rounds using Federal 36 grain value pack ammo.

This is better performance than I got out of my 10/22 using the same ammo! I'm impressed. It has been very windy, and I forgot to bring my sandbags to the range so I can't say anything about the accuracy yet. But the functioning and reliability were excellent for a brand new kit with no break-in period using cheap ammo.