Warning: Excessive detail ahead. Not responsible for injury or brain death caused by boredom.
To date the only .22LR firearm I’ve owned is my Savage MKII. I don’t hunt so .22s have limited uses for me other than fun (and my budget dictates that functional guns get priority over fun guns). Lately though I’ve been craving a semi-auto .22 and, after scoring 5 Winchester 555 bulk boxes in one day, I decided I needed something to shoot them through. I’d done a bunch of research and went with the CMMG .22 drop in conversion bolt for my AR, and I thought I’d share my initial experience.
I bought the kit from American Weapon Systems in Rindge for $170 with a mag, and another $15 for a spare mag. That price seemed low based on what I’d seen online so I emailed CMMG and they confirmed that despite AWS only recently getting the kit, it is an older production model that’s a little different than the new ones. Not a big deal though, since this is for training/fun and not intended for an application where it has to be the best of the best.
What It Is:
For those who don’t know, this design of .22 conversion is a fully self-contained bolt and sub-chamber for the AR platform. All you do is slide out your 5.56 BCG, slide in the conversion bolt, slap in a .22 mag and you’re ready to go. The charging handle still works just like with the normal 5.56 setup and all your controls and parts still do what they normally do with one exception. The bolt catch is non-functional with a .22 conversion (though if you have a new-production CMMG conversion kit, they sell a bolt hold open adapter that makes it functional).
For me the appeal of this kit is training, as I can run it in my normal AR setup with full weight and all the same feels (albeit with less recoil and blast) and it costs $27 for 550 rounds as opposed to $200. That makes a serious day of drills about the same cost as 3 mags of .223, or 2 mags of 5.56. It’s a great value prospect if you can find the ammo to feed it.
Technical Stuff:
The kit is blowback operated, rather than relying on the gas system of the AR. This doesn’t mean however that gas (and crud from the dirty .22 ammo) doesn’t come back through the gas tube. In reality your receiver gets much dirtier than firing an equivalent quantity of .223/5.56. Something I read in researching the kit is to be sure to fire 10-20 rounds of full power 5.56 after a range session with .22. This will blast lead and powder build up out of the gas tube. I did this after my 400-round range session and you can tell from the extra smoke that it was doing something.
I’ll get to accuracy in a minute, but from a technical perspective anyway a .22 bullet is actually .223” in diameter while a .223/5.56 is actually .224”. That means there’s a bit more play when the round is heading down the barrel.
Reliability:
I fired a total of 400 rounds through the kit, representing 4 different loads.
The four loads tested were as follows:
American Eagle 38gr CPHP
Winchester SuperX (bulk) 36gr CPHP
CCI Mini Mag 36gr CPHP
CCI AR Tactical 40gr CPRN
You’ll notice they’re all copper plated. I have a few LRN loads but I’ve read about developing a lead plug in the gas port using lead ammo, so I’m going to avoid that and stick to copper plated ammo.
Between my experience and online videos I watched, I’ve observed that ejection pattern consistency seems to be directly related to how reliable a particular load is going to be.
American Eagle ejected fairly consistently and out of 50 rounds I had zero malfunctions.
Winchester ejected quite consistently most of the time but (typical with this ammo…) it’s the 1% of the rounds that have an issue which have a major issue. I get the same thing with accuracy with Winchester SuperX our of my Savage. It’ll shoot sub-MOA for 99 rounds without exception, then on the 100th round it’ll throw one two inches off. I fires 250 rounds of Winchester SuperX since that’s what I have a lot of. It seemed to work nicely except for priming issues on a few rounds. I had one round fail to go off, one double feed, and two instances of a rather concerning condition which I’m not 100% sure really happened…. The recoil with this setup is so light that I could have just heard an echo, but twice I think it’s possible that one pull of the trigger touched off two rounds, and not because of two falls of the hammer (as my gun is definitely semi-auto with a reliable trigger/hammer group) but because of a slam fire. If it did indeed fire two (again I’m not sure if it did or didn’t) it seems it might have been because of the firing pin just touching the rim of the round and the Winchester SuperX specifically having light primers. This condition that may or may not have happened did only seem to have possibly happened with Winchester. Bottom line here is that I think it’s more an issue with the round than anything. I’m going to pay attention to this in future and if I confirm that it has happened I’ll be sending it in to CMMG (not looking to inadvertently break any laws due to equipment malfunctions).
CCI Mini Mags didn’t eject all that consistently but they functioned flawlessly and, as you’ll see in the accuracy section, they might be the best overall round in the gun.
CCI AR Tactical ran great until it suffered a catastrophic malfunction. When I say catastrophic I don’t mean it blew up, but a condition in which clearing the malfunction was not possible without disassembly and tools. The shell was totally wedged as you see in the pictures and I was only able to pull the bolt group 1/4 inch out before it became wedged and I needed to use pliers to get it out. No damage but quite a jam!
Bottom line on reliability is that it’s just fine for what this is. My only concern is the bump fires that I don’t know for sure really happened. I’ve never heard of this reported before so if it is happening with mine, it’s likely an isolated occurrence.
Accuracy:
Okay so this might be the most interesting part. I experienced a more dramatic spread in my results than I’d seen in videos and articles in my research. This was likely because I tested more rounds and tried to be more scientific.
The procedure was as follows.
All groups were shot at 25 yards. There was a bit of a variable breeze but at only 25 yards that shouldn’t be a major factor. Shooting was done off bags and for reference I’m not a world class marksman but I’m good enough to legitimately shoot a .8” group at 100yds with my Savage, so these results should be pretty decent as compared to what is possible.
I started with 3 rounds of 55gr FMJ 5.56, which is what my gun is zeroed for. That’s the target on the bottom right and the group measures .315” center to center (1.25MOA). Those are low because I’m zeroed for 50yds.
Next I ran a bore snake through the gun. Then I followed the following process for each load tested. I switched to the CMMG bolt, then fired 25 rounds of the load being tested, before shooting a 10-round group. After shooting each 10-round group, I’d shoot 15 more rounds of that load, switch back to 5.56, fire 4 rounds of that, then run the bore snake through. This way each 10 round group was shot with a mostly-clean barrel, plus 25 rounds of that same load.
The results were interesting.
The bottom left is American Eagle. That group is centered about an inch low and to the right of zero and is 3.25” center to center. In other words it’s 13MOA, which could also be pretty much called minute of torso at 100yds. The good news is this was the worst performer and if you held center of mass at 100yds on a silhouette target, they’d all hit it.
Middle left was Winchester SuperX. This centered about 1.5” low and left of zero and is 2.33” (9.33MOA).
Top left is CCI Mini Mags. These centered about an inch to the left and slightly low of zero and measured a respectable 1.07” (4.25MOA). If I had a ton of Mini Mags on hand and didn’t mind the cost, this would be the best of what I tested overall. It was reliable and grouped only slightly larger than crappy range .223 ammo would.
The middle right target is the CCI AR ammo. It centered just half an inch low left of zero and managed a .875” group (3.5MOA). That’s on par with range .223, proving that with the right ammo it can be done.
A lot of people talk about over stabilization being an issue when putting .22LR through an AR barrel (mine is a 1:7 Daniel Defense CHF 16”). I think this is BS below 100 yards (maybe further). Yes I know overspinning can lead to a nose-up attitude on the bullet which makes it less aerodynamic when dropping steeply downrange. Inside 100 yards this isn’t going to be a major factor here and in my opinion the groups vs bullet weight prove that there’s no real correlation here. Better quality rounds did better. The end. The reason shooting .22LR from an AR barrel doesn’t lead to great accuracy is that extra 1000th of an inch diameter. It stands to reason that that would limit accuracy and I think that’s the more significant factor here.
Also regarding bullet drop… I didn’t measure it exactly but I gauged drop by shooting at a plate at 100yds and I had to hold about 18 inches above it to get consistent hits.
Overall accuracy is acceptable for training but might be sub-par if you want this setup for plinking. For example the only round here that would hit a coke can at 50yds every time is the CCI AR Tactical. Even Mini Mags would miss 2 or so in 10 and good luck with the Winchester or American Eagle.
For silhouette blasting and drills though, this is great within 50yds and acceptable to 100.
Overview:
I’m looking forward to getting another few hundred rounds through the kit to see if little things smooth out, but overall this seems like a great setup and I’m glad I bought it.
To date the only .22LR firearm I’ve owned is my Savage MKII. I don’t hunt so .22s have limited uses for me other than fun (and my budget dictates that functional guns get priority over fun guns). Lately though I’ve been craving a semi-auto .22 and, after scoring 5 Winchester 555 bulk boxes in one day, I decided I needed something to shoot them through. I’d done a bunch of research and went with the CMMG .22 drop in conversion bolt for my AR, and I thought I’d share my initial experience.
I bought the kit from American Weapon Systems in Rindge for $170 with a mag, and another $15 for a spare mag. That price seemed low based on what I’d seen online so I emailed CMMG and they confirmed that despite AWS only recently getting the kit, it is an older production model that’s a little different than the new ones. Not a big deal though, since this is for training/fun and not intended for an application where it has to be the best of the best.
What It Is:
For those who don’t know, this design of .22 conversion is a fully self-contained bolt and sub-chamber for the AR platform. All you do is slide out your 5.56 BCG, slide in the conversion bolt, slap in a .22 mag and you’re ready to go. The charging handle still works just like with the normal 5.56 setup and all your controls and parts still do what they normally do with one exception. The bolt catch is non-functional with a .22 conversion (though if you have a new-production CMMG conversion kit, they sell a bolt hold open adapter that makes it functional).
For me the appeal of this kit is training, as I can run it in my normal AR setup with full weight and all the same feels (albeit with less recoil and blast) and it costs $27 for 550 rounds as opposed to $200. That makes a serious day of drills about the same cost as 3 mags of .223, or 2 mags of 5.56. It’s a great value prospect if you can find the ammo to feed it.
Technical Stuff:
The kit is blowback operated, rather than relying on the gas system of the AR. This doesn’t mean however that gas (and crud from the dirty .22 ammo) doesn’t come back through the gas tube. In reality your receiver gets much dirtier than firing an equivalent quantity of .223/5.56. Something I read in researching the kit is to be sure to fire 10-20 rounds of full power 5.56 after a range session with .22. This will blast lead and powder build up out of the gas tube. I did this after my 400-round range session and you can tell from the extra smoke that it was doing something.
I’ll get to accuracy in a minute, but from a technical perspective anyway a .22 bullet is actually .223” in diameter while a .223/5.56 is actually .224”. That means there’s a bit more play when the round is heading down the barrel.
Reliability:
I fired a total of 400 rounds through the kit, representing 4 different loads.
The four loads tested were as follows:
American Eagle 38gr CPHP
Winchester SuperX (bulk) 36gr CPHP
CCI Mini Mag 36gr CPHP
CCI AR Tactical 40gr CPRN
You’ll notice they’re all copper plated. I have a few LRN loads but I’ve read about developing a lead plug in the gas port using lead ammo, so I’m going to avoid that and stick to copper plated ammo.
Between my experience and online videos I watched, I’ve observed that ejection pattern consistency seems to be directly related to how reliable a particular load is going to be.
American Eagle ejected fairly consistently and out of 50 rounds I had zero malfunctions.
Winchester ejected quite consistently most of the time but (typical with this ammo…) it’s the 1% of the rounds that have an issue which have a major issue. I get the same thing with accuracy with Winchester SuperX our of my Savage. It’ll shoot sub-MOA for 99 rounds without exception, then on the 100th round it’ll throw one two inches off. I fires 250 rounds of Winchester SuperX since that’s what I have a lot of. It seemed to work nicely except for priming issues on a few rounds. I had one round fail to go off, one double feed, and two instances of a rather concerning condition which I’m not 100% sure really happened…. The recoil with this setup is so light that I could have just heard an echo, but twice I think it’s possible that one pull of the trigger touched off two rounds, and not because of two falls of the hammer (as my gun is definitely semi-auto with a reliable trigger/hammer group) but because of a slam fire. If it did indeed fire two (again I’m not sure if it did or didn’t) it seems it might have been because of the firing pin just touching the rim of the round and the Winchester SuperX specifically having light primers. This condition that may or may not have happened did only seem to have possibly happened with Winchester. Bottom line here is that I think it’s more an issue with the round than anything. I’m going to pay attention to this in future and if I confirm that it has happened I’ll be sending it in to CMMG (not looking to inadvertently break any laws due to equipment malfunctions).
CCI Mini Mags didn’t eject all that consistently but they functioned flawlessly and, as you’ll see in the accuracy section, they might be the best overall round in the gun.
CCI AR Tactical ran great until it suffered a catastrophic malfunction. When I say catastrophic I don’t mean it blew up, but a condition in which clearing the malfunction was not possible without disassembly and tools. The shell was totally wedged as you see in the pictures and I was only able to pull the bolt group 1/4 inch out before it became wedged and I needed to use pliers to get it out. No damage but quite a jam!
Bottom line on reliability is that it’s just fine for what this is. My only concern is the bump fires that I don’t know for sure really happened. I’ve never heard of this reported before so if it is happening with mine, it’s likely an isolated occurrence.
Accuracy:
Okay so this might be the most interesting part. I experienced a more dramatic spread in my results than I’d seen in videos and articles in my research. This was likely because I tested more rounds and tried to be more scientific.
The procedure was as follows.
All groups were shot at 25 yards. There was a bit of a variable breeze but at only 25 yards that shouldn’t be a major factor. Shooting was done off bags and for reference I’m not a world class marksman but I’m good enough to legitimately shoot a .8” group at 100yds with my Savage, so these results should be pretty decent as compared to what is possible.
I started with 3 rounds of 55gr FMJ 5.56, which is what my gun is zeroed for. That’s the target on the bottom right and the group measures .315” center to center (1.25MOA). Those are low because I’m zeroed for 50yds.
Next I ran a bore snake through the gun. Then I followed the following process for each load tested. I switched to the CMMG bolt, then fired 25 rounds of the load being tested, before shooting a 10-round group. After shooting each 10-round group, I’d shoot 15 more rounds of that load, switch back to 5.56, fire 4 rounds of that, then run the bore snake through. This way each 10 round group was shot with a mostly-clean barrel, plus 25 rounds of that same load.
The results were interesting.
The bottom left is American Eagle. That group is centered about an inch low and to the right of zero and is 3.25” center to center. In other words it’s 13MOA, which could also be pretty much called minute of torso at 100yds. The good news is this was the worst performer and if you held center of mass at 100yds on a silhouette target, they’d all hit it.
Middle left was Winchester SuperX. This centered about 1.5” low and left of zero and is 2.33” (9.33MOA).
Top left is CCI Mini Mags. These centered about an inch to the left and slightly low of zero and measured a respectable 1.07” (4.25MOA). If I had a ton of Mini Mags on hand and didn’t mind the cost, this would be the best of what I tested overall. It was reliable and grouped only slightly larger than crappy range .223 ammo would.
The middle right target is the CCI AR ammo. It centered just half an inch low left of zero and managed a .875” group (3.5MOA). That’s on par with range .223, proving that with the right ammo it can be done.
A lot of people talk about over stabilization being an issue when putting .22LR through an AR barrel (mine is a 1:7 Daniel Defense CHF 16”). I think this is BS below 100 yards (maybe further). Yes I know overspinning can lead to a nose-up attitude on the bullet which makes it less aerodynamic when dropping steeply downrange. Inside 100 yards this isn’t going to be a major factor here and in my opinion the groups vs bullet weight prove that there’s no real correlation here. Better quality rounds did better. The end. The reason shooting .22LR from an AR barrel doesn’t lead to great accuracy is that extra 1000th of an inch diameter. It stands to reason that that would limit accuracy and I think that’s the more significant factor here.
Also regarding bullet drop… I didn’t measure it exactly but I gauged drop by shooting at a plate at 100yds and I had to hold about 18 inches above it to get consistent hits.
Overall accuracy is acceptable for training but might be sub-par if you want this setup for plinking. For example the only round here that would hit a coke can at 50yds every time is the CCI AR Tactical. Even Mini Mags would miss 2 or so in 10 and good luck with the Winchester or American Eagle.
For silhouette blasting and drills though, this is great within 50yds and acceptable to 100.
Overview:
I’m looking forward to getting another few hundred rounds through the kit to see if little things smooth out, but overall this seems like a great setup and I’m glad I bought it.
