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Discussion Starter #1
So I bought a CMMG Ar-15 today, and the guy I bought it from says it is chambered in 5.56/.223. I've looked all over this thing for a stamping, all over the barrel, and the upper in general. The lower is stamped 5.56/.223 but that doesn't matter. What's the easiest way to tell short of having to buy something? If that's what has to happen I'll just shoot .223 out of it.
 

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Pull the hand guards and see if it has any barrel stampings. The actual upper doesn't care. it is the barrel and extension that should be marked
 

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Is there a twist rate ie 1/7 or 1/9 also look for a NATO stamp on the barrel
 

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If its 1:7 then it should be fine with 5.56 don't quote me on it though. Also run a rod with a brush down the barrel with marks so you can measure when it makes 1 full turn then measure how far it traveled in that one full turn
 

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Discussion Starter #8
After reading there, and a couple other sites, looks like I just have an unmarked one. Possibly a blem or something..
No big deal, but it would be nice to know if I could run surplus ammo through it..

If its 1:7 then it should be fine with 5.56 don't quote me on it though. Also run a rod with a brush down the barrel with marks so you can measure when it makes 1 full turn then measure how far it traveled in that one full turn
Good call, I'll do that in the am.
 

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Go here and decide what profile barrel you have.

http://www.cmmginc.com/Articles.asp?ID=266

Then look around and find a CMMG rifle chambered in only .223.

Rifles

Then go to their barrels and find one in .223.

Barrels

If all else fails, call them with the serial # and ask them.

One way or another, the barrel is stamped.
 

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If its 1:7 then it should be fine with 5.56 don't quote me on it though. Also run a rod with a brush down the barrel with marks so you can measure when it makes 1 full turn then measure how far it traveled in that one full turn




Barrel twist is in no way connected to the chambering.



It *should* be marked on the barrel. Usually top or side, just in front of the front sight. Sometimes it'll be marked and covered by the handguards, all as mentioned above.


If all else fails, take a mic to the bore at the muzzle and measure it. That'll give you at least caliber.


Easiest way would be to take to a gunsmith and have them check. Shouldn't cost much (if anything) for the 10 seconds of work they need to check it...
 

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Discussion Starter #11
Go here and decide what profile barrel you have.

http://www.cmmginc.com/Articles.asp?ID=266

Then look around and find a CMMG rifle chambered in only .223.

Rifles

Then go to their barrels and find one in .223.

Barrels

If all else fails, call them with the serial # and ask them.

One way or another, the barrel is stamped.
Hell after looking around there, it doesn't even look like they sell one in .223.

Barrel twist is in no way connected to the chambering.



It *should* be marked on the barrel. Usually top or side, just in front of the front sight. Sometimes it'll be marked and covered by the handguards, all as mentioned above.


If all else fails, take a mic to the bore at the muzzle and measure it. That'll give you at least caliber.


Easiest way would be to take to a gunsmith and have them check. Shouldn't cost much (if anything) for the 10 seconds of work they need to check it...
It's not marked at all on the barrel. Not under the handguards, not anywhere. Only a G under the handguards, on the bottom of the barrel.
I guess I'll just call them and ask. Just figured there was an easy way to look and see.
 

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Discussion Starter #13
Yeah, seems to be relatively common. Oh well. I'll just call them Monday and see what they have to say. I'd say it's 5.56 considering they don't list a .223 chamber on their site, but I'd rather ask to make sure.
 

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So to add onto this, what if its a 5.56 and you shoot 223 and the other way round?
 

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So to add onto this, what if its a 5.56 and you shoot 223 and the other way round?
5.56 will shoot 223 but 5.56 has a higher pressure then 223 so you can figure out what could happen
 

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So to add onto this, what if its a 5.56 and you shoot 223 and the other way round?




One way will cause your rifle to explode in an apocalyptic firey inferno destroying the entire universe. The other will get you laffed at by your local "tacticool" crowd because you're not shooting mil-spec, and thus, not qualified to be on the range.
 

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I doubt you will find a non-match barrel AR built in the last 20 years that won't shoot 5.56 anywhere...
 
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