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  1. #1
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    Default CMMG 6.8 bbl ???

    What are the pros and cons? I am having a lil trouble finding reviews for this bbl. I am looking at either a 16" or 18" with mid gas. It will be used mostly for hunting and maybe even some local carbine matches.

    Thanks

  2. #2
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    CMMG's newer spec'd barrels with the SPC II, 1:11 twist, 4-groove, chrome lined features came out late in the Spring and early Summer. They quietly moved to the preferred specs a little ahead of some of the other big AR companies like Bushmaster, DPMS, and Armalite. They do use 4150 barrel steel and MPI test their barrels. A few on the forum have purchased them recently, and we've seen one of their new barrels with CMMG's piston system upgrade.

    Here's a post from not too long ago:

    http://68forums.com/forums/showthrea...highlight=cmmg

    Their previous barrels were SPC II chamber and 1:10 twist. The specs on the newer ones are much better. 16-18 inch barrel with midlength gas would be good combos with their new specs.

    There have been some discussion threads on AR15.com in CMMG's Industry Forum about these barrels. Plus, CMMG staff participate in their AR15.com forum if you wanted to ask them questions direct through AR15.com.
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  3. #3
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    CMMG usually makes nice stuff, most of the time overlooked by the brand snobs but all I have ever seen from them was quality products.

    I would skip the chrome lining if I could since all it does is increase pressure and degrades accuracy IMO, I dont see why so many people that's rifles will never see harsh environments or not get cleaned after every range trip think chrome lining is necessary.

    Most non-chrome line CMV barrels are more accurate than their chrome lined counter parts, just as a SS barrel it's more accurate since it has no lining to affect accuracy. I have seen several reviews and one good one one here were two rifles were excluded from testing because a pin gauge wouldn't pass through the barrel because the chrome lining was thicker in some spots, this not only degrades accuracy but increases pressure and decreases MV which in my book is not a good thing.

    My next barrel will be SS or CMV with no chrome lining, although there are some good linings being used like the Nitride coatings which are smooth and dont affect accuracy(some even help) or pressure like most CL barrels do.

    Not saying all chrome lined barrels are bad or created equal, but from what I have seen a non lined barrel is mostly always more accurate and no worries about rusting or corrosion which is what chrome lining was designed for, that and a little longer barrel life which I would trade for more accuracy any day.

  4. #4
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    Quote Originally Posted by EWP View Post
    CMMG usually makes nice stuff, most of the time overlooked by the brand snobs but all I have ever seen from them was quality products.

    I would skip the chrome lining if I could since all it does is increase pressure and degrades accuracy IMO, I dont see why so many people that's rifles will never see harsh environments or not get cleaned after every range trip think chrome lining is necessary.

    Most non-chrome line CMV barrels are more accurate than their chrome lined counter parts, just as a SS barrel it's more accurate since it has no lining to affect accuracy. I have seen several reviews and one good one one here were two rifles were excluded from testing because a pin gauge wouldn't pass through the barrel because the chrome lining was thicker in some spots, this not only degrades accuracy but increases pressure and decreases MV which in my book is not a good thing.

    My next barrel will be SS or CMV with no chrome lining, although there are some good linings being used like the Nitride coatings which are smooth and dont affect accuracy(some even help) or pressure like most CL barrels do.

    Not saying all chrome lined barrels are bad or created equal, but from what I have seen a non lined barrel is mostly always more accurate and no worries about rusting or corrosion which is what chrome lining was designed for, that and a little longer barrel life which I would trade for more accuracy any day.
    ArtFWTx

    CMMG's newer spec'd barrels with the SPC II, 1:11 twist, 4-groove, chrome lined features came out late in the Spring and early Summer. They quietly moved to the preferred specs a little ahead of some of the other big AR companies like Bushmaster, DPMS, and Armalite. They do use 4150 barrel steel and MPI test their barrels. A few on the forum have purchased them recently, and we've seen one of their new barrels with CMMG's piston system upgrade
    EWP, I ordered a few small things from CMMG the other day and out of curiosity I asked about their 6.8 barrels and what ART quoted is what they have i.e. 4150 CL. They don't have the 6.8 in the 4140 CM, only the M4LE series from what I understand from my conversation with them. I would be interested is what kind of accuracy people are getting in CL vs CM in the 6.8. I have ARs in 5.56 , some are CL , some aren't and I honestly haven't noticed any signifigant difference in accuracy. Of course YMMV. I am also interested in how the piston uppers are performing.

  5. #5

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    I've never used one of their barrels in 6.8, but I've had a couple in 5.56 and they were extremely accurate (CL). On the down side, several threads concerning their thread concentricity being off have cropped up over the years. Not a big deal unless you are planning on running a suppressor.

    Both of my CMMG uppers suffered from baffle strikes and destroyed the AAC cans, but I don't believe thread concentricity had anything to do with either of them since the round count was at least 1100-1200 each time. Still, when I had the 2nd can rebuilt, AAC told me that they would not be responsible for what happened if I ever put one of their products on a CMMG barrel again, so I changed to an LMT and have been pretty happy.

    The first CMMG upper (10.3" SG with an M42k can) was the most accurate short AR that I've ever had though. In 2006 it smacked steel torsos at 400m using crappy Remington UMC ammo at a school in Nacadotches, TX. with monotonous regularity. I was amazed!

    A little off topic, sorry, but in my experience CMMG barrels are accurate and GTG! Just know that you might get a little flack from suppressor manufacturers if you use them on a CMMG barrel.


    Saleen

  6. #6
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    You can still have an accurate chrome lined barrel. It depends on the quality control in place by the manufacturer and the specs they demand from their finished CL'd barrels. If QC isn't there, then you can have issues with chrome lining as we've seen before.

    If you're after all the accuracy you can get and want a true tightly spec'd match barrel, you will not be buying one with chrome lining. However a good chrome lined barrel can shoot MOA or better if the quality is there.
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  7. #7
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    Quote Originally Posted by Saleen View Post
    I've never used one of their barrels in 6.8, but I've had a couple in 5.56 and they were extremely accurate (CL). On the down side, several threads concerning their thread concentricity being off have cropped up over the years. Not a big deal unless you are planning on running a suppressor.

    Both of my CMMG uppers suffered from baffle strikes and destroyed the AAC cans, but I don't believe thread concentricity had anything to do with either of them since the round count was at least 1100-1200 each time. Still, when I had the 2nd can rebuilt, AAC told me that they would not be responsible for what happened if I ever put one of their products on a CMMG barrel again, so I changed to an LMT and have been pretty happy.

    The first CMMG upper (10.3" SG with an M42k can) was the most accurate short AR that I've ever had though. In 2006 it smacked steel torsos at 400m using crappy Remington UMC ammo at a school in Nacadotches, TX. with monotonous regularity. I was amazed!

    A little off topic, sorry, but in my experience CMMG barrels are accurate and GTG! Just know that you might get a little flack from suppressor manufacturers if you use them on a CMMG barrel.


    Saleen
    Yeah, CMMG had to deal with that issue. I do not have a can and CMMG barrel so I can't comment on whether that issue is resolved, but CMMG said it was resolved. Saleen's comments are worth consideration if you have a can. It'd be worth a conversation with CMMG before combining the two of your own.

    My brothers 14.5 in CMMG upper is very nice and he'd buy another.
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  8. #8
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    Quote Originally Posted by Lucky View Post
    ArtFWTx



    EWP, I ordered a few small things from CMMG the other day and out of curiosity I asked about their 6.8 barrels and what ART quoted is what they have i.e. 4150 CL. They don't have the 6.8 in the 4140 CM, only the M4LE series from what I understand from my conversation with them. I would be interested is what kind of accuracy people are getting in CL vs CM in the 6.8. I have ARs in 5.56 , some are CL , some aren't and I honestly haven't noticed any signifigant difference in accuracy. Of course YMMV. I am also interested in how the piston uppers are performing.
    Most CL barrels are pretty accurate and most here with them will agree that all barrels aren't created equal, but I have no first hand experience with a bad one my DD & Colt barrels are CL and they both shoot great but if I were looking for best accuracy I would buy a none CL(doesn't have to be 4140), SS, or a Nitride coated barrel as they tend to be a little more accurate than their CL counterparts. I'm sure the CMMG barrels are GTG and very accurate as well, I dont hear many people complaining about CMMG's products.

  9. #9
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    Quote Originally Posted by EWP View Post
    Most CL barrels are pretty accurate and most here with them will agree that all barrels aren't created equal, but I have no first hand experience with a bad one my DD & Colt barrels are CL and they both shoot great but if I were looking for best accuracy I would buy a none CL(doesn't have to be 4140), SS, or a Nitride coated barrel as they tend to be a little more accurate than their CL counterparts. I'm sure the CMMG barrels are GTG and very accurate as well, I dont hear many people complaining about CMMG's products.
    My only 68 is stainless Bison, but I have a Stag CL, A CMMG with the WASP and a Del-Ton CM in 5.56 , also my DPMS 308 is CM. I have to agree with you that I've always been under the assumption that non- CL barrels tend to be more accurate and probably are in the hands of a good shooter, but I'm not good enough to know the difference. Also I don't hear many complaints about CMMG either. Don't the competition shooters use SS barrels now days or it that just internet BS ?

  10. #10
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    Well you shot my plans out the window. Over the last few days i have been leaning more towards either the 14.5" or 16" because i plan to "Can It" I guess i could always call them and ask if they would be willing to warrenty the can as well as thier bbl if there is a problem.


 

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