AR Build with CMMG 22LR conversion - Question

thperez1972 · Sep 2, 2017

My 11 year old step daughter and I will be building an AR rifle with a CMMG 22LR Bravo Conversion Kit. The plan is, once she is comfortable with the rifle we can switch out the BCG. That way, the only major change is the recoil but she will be comfortable with the rifle. While talking to someone familiar with firearms, they suggested using a dedicated 22LR barrel from CMMG. Their reasoning is that would keep the dirty gasses out of the upper receiver.

After I left and thought about it a while, I thought to myself, wouldn't leaving off the gas tube or even the gas block do that as well? Sure, but some gas would still escape through the hole. But if I installed the gas block backwards, it would simply act as a plug for the hole. The rifle will have a free float handguard. I can't really think of a reason to not just put the gas block on backwards. Can anyone think of any legitimate reason this would not work or would be a bad idea?

rcm192 · Sep 2, 2017

The main reason for a dedicated 22 lr upper is the twist rate to stabilize lighter 22lr projectile weights. The bore diameters are similar so thats what makes the conversion convenient. Although 22 lr is dirty ammo; a magazine or 2 of 223/556 will help out on cleaning up the gas system as the pressures are much higher. Sure plugging up the gas port wouldnt allow build up to accumulate in the tube but its probably not necessary. Your call on that. I would leave your rifle rigged up as is and just shoot 22 and 556 out of it intermittently.

A pistol build with a shorter barrel length and a pistol brace may be more beneficial for the little one because it wont be as front heavy.

beauxdog · Sep 3, 2017

A dedicated upper is the way to go. They are more accurate and function better. Don't think you will be happy using a conversion bolt.

Beauxdog

Candyman · Sep 3, 2017

I have the HK 416D and the Sig 522. They are both great guns and cost about the same as a dedicated 22lr upper.
The CMMG 22 conversation would be more versatile. If your daughter ever wants to try out one of your other ARs, you can just swap out the BCG.
I would not worry about the carbon build up from the 22lr ammo. Just get a standard BCG for her rifle and shoot a few rounds of 556 before leaving the range.
My 13yo just finished his 2nd build, a Red & Black AR. We used the GunTec lightweight rail and a lightweight barrel. It has great balance and is not front heavy.

thperez1972 · Sep 3, 2017

rcm192 said:
The main reason for a dedicated 22 lr upper is the twist rate to stabilize lighter 22lr projectile weights. The bore diameters are similar so thats what makes the conversion convenient. Although 22 lr is dirty ammo; a magazine or 2 of 223/556 will help out on cleaning up the gas system as the pressures are much higher. Sure plugging up the gas port wouldnt allow build up to accumulate in the tube but its probably not necessary. Your call on that. I would leave your rifle rigged up as is and just shoot 22 and 556 out of it intermittently.

A pistol build with a shorter barrel length and a pistol brace may be more beneficial for the little one because it wont be as front heavy.

Thanks for the on-topic reply. The rifle hasn't been built so I have the option to rig it up however I want. With the end result being the same, I'll likely just mis-install the gas block. That seems easier and about $20 per cleaning cheaper.

- - - Updated - - -

beauxdog said:
A dedicated upper is the way to go. They are more accurate and function better. Don't think you will be happy using a conversion bolt.

Beauxdog

Thank you for your reply. It is off-topic so I will not address the particulars mentioned in the post.

thperez1972 · Sep 3, 2017

Candyman said:
I have the HK 416D and the Sig 522. They are both great guns and cost about the same as a dedicated 22lr upper.
The CMMG 22 conversation would be more versatile. If your daughter ever wants to try out one of your other ARs, you can just swap out the BCG.
I would not worry about the carbon build up from the 22lr ammo. Just get a standard BCG for her rifle and shoot a few rounds of 556 before leaving the range.
My 13yo just finished his 2nd build, a Red & Black AR. We used the GunTec lightweight rail and a lightweight barrel. It has great balance and is not front heavy.
View attachment 73028

I have a lightweight rail for her build. And a bipod. She doesn't like shooting from the standing position, even my AR 10.5" pistol. I have a bipod for her to use to help her in the prone position. Once she's comfortable, we can work on prone unsupported. But she wants to paint hers with a pink cheetah print.

thperez1972 · Sep 3, 2017

beauxdog said:
A dedicated upper is the way to go. They are more accurate and function better. Don't think you will be happy using a conversion bolt.

Beauxdog

Thank you for your reply. Your reply is off-topic and the particulars in your post will not be addressed at this time.

shrxfn · Sep 5, 2017

Nobody has mentioned this and not sure if it is on topic but have you thought about putting an adjustable gas block on the upper? You can turn the gas off for 22lr and then back on for reduced recoil on 5.56. Just remember to count the clicks to get the minimum amount of gas to cycle the 5.56.

kingfhb · Sep 5, 2017

This is an 11 year old... no indication the child will be competing in 3 gun competitions... The CMMG .22LR conversion is a great tool and kit... the Mags function well, the bolt is easy to adapt... don't spend or waste any outrageous amount on a full upper. I'm not sure how much "ACCURACY" anyone is really expecting from .22LR in the first place.

Plink and enjoy... it's not going to ruin your upper... you can mitigate junk by shooting quality ammo (which is still dirty, don't get me wrong).

thperez1972 · Sep 5, 2017

shrxfn said:
but have you thought about putting an adjustable gas block on the upper?

Nope...not until you suggested it. It is something I may consider.

thperez1972 · Sep 5, 2017

kingfhb said:
This is an 11 year old... no indication the child will be competing in 3 gun competitions... The CMMG .22LR conversion is a great tool and kit... the Mags function well, the bolt is easy to adapt... don't spend or waste any outrageous amount on a full upper. I'm not sure how much "ACCURACY" anyone is really expecting from .22LR in the first place.

Plink and enjoy... it's not going to ruin your upper... you can mitigate junk by shooting quality ammo (which is still dirty, don't get me wrong).

Even with the suggestions, I was not going with a dedicated upper. The .22LR kit was to get her comfortable. If she wants to work on any sort of accurate 22 shooting, she can use the 10/22. It's been upgraded so it should be a little more accurate than the AR would be.

I'm glad someone sees the goal of this build is not accuracy but familiarization. If I buy her a dedicated upper, then she's shooting with daddy's rifle. The goal is for her to build a rifle that she can upgrade over time. Switching out an upper is more than upgrading a rifle. It's replacing half the rifle.

I didn't think the gasses would hurt the upper. I would just rather keep it as clean as possible. I couldn't think of any reason why plugging the hole would be bad so I decided to post the question so people who know more than I do could weigh in if I missed something. Sometimes I forget the option to post is open to everyone, not just those who know more than I do.

topgunz1 · Sep 5, 2017

I had a conversion kit before I got a dedicated upper, it worked great and was plenty accurate enough for plinking in a 1 in 9 twist upper. I'd always shoot a mag of .223 through it to blow out the gas system at the end of the day. The only issue I ever had was after a bunch of .22 it was very dirty and didn't function right. I lubed the crap out of the upper and it ran fine after that.

Black Dog Machine were the mags to have back in the day, I'm not sure what the go-to is nowadays with the newer kits.

thperez1972 · Sep 6, 2017

topgunz1 said:
I'd always shoot a mag of .223 through it to blow out the gas system at the end of the day.

And that made me post my question. Since the rifle is not yet built, I could remove the need for blowing out the gas system by simply installing the gas block backwards. I can't find any reason that would cause an issue. When it comes time to move to .223, a little minor gunsmithing and she's good to go.

jdindadell · Sep 29, 2017

My buddy used a conversion on his S&W ar and had issues when he went back to 223. I took the gun apart and eventually removed the gas block. The gas port was leaded up, completely. There was even some lead in the gas block. He had shot a fair amount of 22lr through the gun, maybe 1500 rounds.

That is enough for me to recommend a dedicated upper, or complete rifle.

22lr plinking ammo is dirty. I would never run it through a nice gun. And once you go to match ammo the prices rise and just shooting 223 looks like a better idea to me.

thperez1972 · Sep 29, 2017

jdindadell said:
My buddy used a conversion on his S&W ar and had issues when he went back to 223. I took the gun apart and eventually removed the gas block. The gas port was leaded up, completely. There was even some lead in the gas block. He had shot a fair amount of 22lr through the gun, maybe 1500 rounds.

That is enough for me to recommend a dedicated upper, or complete rifle.

22lr plinking ammo is dirty. I would never run it through a nice gun. And once you go to match ammo the prices rise and just shooting 223 looks like a better idea to me.

That's exactly why I was thinking of installing the gas port backwards. The gas hole would be blocked and no gas would get into the gas block itself. I'm pretty sure the 11 year old doesn't need a tack driver so we're going with a much less expensive, "good enough" build. It's not a "nice gun." It's a "let the 11 get comfortable" gun. When she's ready to step up to 223, we'll just replace the barrel if needed.

noob · Sep 29, 2017

I had a CMMG kit (stainless) a long time ago, but sold it b/c my 10/22's were less ammo sensitive and more reliable. Plus I know blowing a few rounds of 5.56 would "blow out" the gas tube, but many times I was shooting 22's in the indoor ranges which do not allow rifle cartridges. I ended up with 3 10/22's (one made to look like an AK, AR, and a G36). And a dedicated 22LR "pistol"

GIJeaux · Sep 30, 2017

As already mentioned, barrel twist is a consideration.
I use an M261 adapter in my A1 with a 1-12" barrel and get great accuracy. When I put it in one of my faster twist barrels like 1-7" the groups open up quickly. In a 1-10" barrel I have, it seems to be the happy medium and gives acceptable results with everything from .22LR to 62gr M855. Things to ponder.

Al

thperez1972 · Sep 30, 2017

GIJeaux said:
As already mentioned, barrel twist is a consideration.
I use an M261 adapter in my A1 with a 1-12" barrel and get great accuracy. When I put it in one of my faster twist barrels like 1-7" the groups open up quickly. In a 1-10" barrel I have, it seems to be the happy medium and gives acceptable results with everything from .22LR to 62gr M855. Things to ponder.

Al

I apologize if this reply sounds short. Although I appreciate all of the suggestions, I've attempted to keep this thread on topic but that has been a challenge. Barrel twist is not a consideration with respect to the topic of the thread. Accurately is not a consideration to the topic of the thread. The topic is any possible issues that might come from installing the gas block backwards to cover the gas port in the barrel. I'm not building a rifle for accuracy in 22lr. The 22lr is for familiarization. Once she's comfortable, I want to convert the rifle to 556 with minimal changes. In this case, switching the bcg and installing the gas tube. That way it will stay the rifle she built and has gotten comfortable with.

rcm192 · Sep 30, 2017

thperez1972 said:
I apologize if this reply sounds short. Although I appreciate all of the suggestions, I've attempted to keep this thread on topic but that has been a challenge. Barrel twist is not a consideration with respect to the topic of the thread. Accurately is not a consideration to the topic of the thread. The topic is any possible issues that might come from installing the gas block backwards to cover the gas port in the barrel. I'm not building a rifle for accuracy in 22lr. The 22lr is for familiarization. Once she's comfortable, I want to convert the rifle to 556 with minimal changes. In this case, switching the bcg and installing the gas tube. That way it will stay the rifle she built and has gotten comfortable with.

JoeLiberty · Oct 2, 2017

As JD suggested you could fill the gas port itself with lead, and yes, that can happen even if the gas block is backward. Maybe that could be pushed out when you remove the gas block? or it might ruin your barrel, who knows? All we can do is guess, since it's quite likely no one has done that before.
I don't know what you are looking to hear. Multiple well informed people have given you pretty good suggestions, based on their own experience. A couple said just run it as-is, it's fine, and the rest said they didn't enjoy their experience with that product at all. One gent even suggested a barrel that gives you great function with both 22lr and 5.56. I mean c'mon if you want minimal changes to convert the rifle, that's it! But you don't want to hear it... It sounds like all you want to hear is "yes, taht's the best idea evar. You are very clever man to figure out". You're obviously gonna do what you're gonna do. So just do it. Let us know how it goes.
Also, if what you want is proper function, be advised that the CMMG kit alone does not do this. The bolt won't lock/release like normal. Certain CMMG mags have an extension to jam the bolt open on the follower, but the bolt closes when you take out the mag.
I highly recommend the boonie packer 'Better-Mag' adapter. It uses M&P 15-22 mags, and restores the bolt lock function. The bolt locks back on empty mag, so you can change mag and drop the bolt with the bolt release. Function is flawless (though I use a dedicated barrel). You can teach her how to clear malfunctions (a good idea). The mags are also easier to load.

AR Build with CMMG 22LR conversion - Question

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