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Old July 14, 2023, 10:25 PM   #1
Join Date: January 8, 2022
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AR-15 22LR conversion and the gas

I'm considering the CMMG 22LR conversion for AR-15, but I have a question: what happens to the gas that enters the gas tube? As much as I can tell, the conversion does not plug the tube. That may actually be a good thing, because doing so would make it plug with carbon, deposited where the gas cools down and/or expands. So, we have the gas just venting into the receiver, right? How much of a problem that is?
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Old July 15, 2023, 03:54 PM   #2
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It is a non-issue.
The wax and lead deposits in the gas block and tube, however, are claimed to be an issue by some people.

(I went to a dedicated .22 LR barrel before shooting enough to see any issues in my .223/5.56 barrels.)
Don't even try it. It's even worse than the internet would lead you to believe.
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Old July 21, 2023, 02:16 PM   #3
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I have never used one of he coversions, but my understanding is that it’s a good idea to periodically fire 5.56mm to blow the build-up from .22LR from the gas port and gas tube.

I do own a dedicated CMMG .22LR upper (have owned it for a decade now), and it is pretty great.
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Old July 21, 2023, 06:43 PM   #4
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Originally Posted by zaitcev View Post
I'm considering the CMMG 22LR conversion for AR-15, but I have a question: what happens to the gas that enters the gas tube?
The gas, carbon and lube (on lead bullets) are a non-issue if you clean it, and or shoot a few .223 rounds through it periodically. There is less gas and carbon, even if the lube burns, than from .223 ammo.

But, if you have a bullet that happens to lead the bore, or you have an old barrel with a worn gas port, yep, you can (not will) create some severe issues.

I've seen some gas tubes with large bulges in them, blown primers and very erratic accuracy from some conversion guns where the barrel was let to be very fouled, and or the gas port was pretty eroded. Usually, it is just some poor accuracy for 10 to 15 rounds while the lead gets blown out.

Copper washed bullets can (not will) mitigate the issue.

Personally, with a .22LR BCG AND barrel being about the same price as a .22 Conversion kit, to me, just build the upper and avoid the potential issues.
Good Shooting, MarkCO
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