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DPMS CMMG PROBLEMS


the bigness

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Thats probably what happened.  My lower is old.  I can't find any mags to use with it.  Its pretty much a useless lower.  Ya think they will exchange it for one with the same serial number?  I bought it brand new.  Not sure the dealer is still in business.

I only have Pmags and DPMS mags.  They only partially work.  Doesn't do me any good.  I hope they stand by their products.

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Thats probably what happened.  My lower is old.  I can't find any mags to use with it.  Its pretty much a useless lower.  Ya think they will exchange it for one with the same serial number?  I bought it brand new.  Not sure the dealer is still in business.

I only have Pmags and DPMS mags.  They only partially work.  Doesn't do me any good.  I hope they stand by their products.

If you can't find or get a Cproducts mag., let me know & I will send you one to try out .

Hell, even the DPMS mags I have work in my CMMG lower . Your DPMS Mags can be tweaked to work ,in most cases.

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Hello people long time no talk. I ended up putting a AR-10 mag release in and CMMG lower and using dummy rounds through all my P-MAGS not one problem. The DPMS VS AR-10 differs  in that the bolt is longer and the shelf that locks the mag in is slightly thicker. Unfortunately I just bought a super moto now it's my new barbie. I can tell you that the mags locked in with a much more solid purchase so that being said, I need get off my bike and go shoot that $3000.00 rifle to be sure my fix is correct. i will let you know if my fix works. My finger has been itching a bit!!!  <thumbsup>

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That's good to hear , Bigness.

I put the AR 10 mag release in mine also & it did tighten it up , but this CMMG lower will not work with Pmags & I am going to live with it that way , as long as the steels work .

usadaytrader

Does the bolt stay back on the last round fired ?

One thing else I would try is , load the mag full & don't use it for a week & see how it works , I had some luck with some of the Pmags that way , but upon leaving them unloaded the same FTF occurred .

Makes you wounder if the mag springs on the PMags are too stiff in some cases. They have a very long spring in them . I will not be altering any of mine ,because they work fine in my DPMS build .

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  • 2 weeks later...

bigness, which one did you pick up?

Yes, all mags lock open on empty mags.

I sent the lower back to CMMG and all they did was remove more material from the magcatch area.  But it still has the same feeding problems.  No mags works.  The lower is worthless.  Minus well of bought a bolt action rifle.  I am requesting a new lower replacement because I am spending too much time and money and ammo for this POS.  A guns worthless if theres no available mags for it.

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FWIW it's worth DPMS made a batch of bad mags a few years ago. The ones you have were they bought at the same time? Lastly not sure if it was discussed in this thread previously but the CMMG was designed before the PMAGs were available and thats why we suspect they dont function in these weapons.

What magazines does CMMG offer?

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FWIW it's worth DPMS made a batch of bad mags a few years ago. The ones you have were they bought at the same time? Lastly not sure if it was discussed in this thread previously but the CMMG was designed before the PMAGs were available and thats why we suspect they dont function in these weapons.

What magazines does CMMG offer?

I don't know. 

Did they change the design of the MK-3?  I know Pmags work fine in Mk-3s.  Anyways, other than the feeding problem, the buffer area on my lower is being gouged by the bolt carrier. 

I respect your feedback, but I feel that using only one type of mag is kind of a half ass fix. 

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  • 2 weeks later...

Can you show a photo of the wear makes on the receiver extension ? Might have some thing to do with function problems.

A lot of these problems can be related to machining tolerances between two different manufactures( upper /lower ).

Yes CMMG changed there lowers that are assembled on there new line of 308 rifles.

Also look on page three , # 36 post on this thread  & you will see the difference in cartridge height & the Pmag ,mag catch position & it is why I am having bolt over on my CMMG . The DPMS & CProducts mags sit higher in my older CMMG lower & that's why they feed correctly .

The Pmag is low enough to let the bolt pass over or have the carrier grab the round & mangle it .

Its probably tolerance stacking as was discussed in this thread .  They probably moved the mag catch up a hair to accommodate the Pmag. on the new lowers, just a guess .

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  • 1 month later...

Talked to CMMG yesterday after (finally) saving enough to buy the upper I wanted to finish my lower and imagine my surprise to find out that my lower is completely out of spec.

To respond to the Magpul PMag issue and tolerance stacking, this is a true fact, and also there seems to be an issue with the bolt catch. The Issue does not stem from the bullet button at all.  Busted out the micrometer today and detailed exact specifications of just about the entire lower now to see what exactly is changed when the milling comes back but am seriously not happy with this experience with what I used to consider a respectable company.

To be fair and honest I sent CMMG quite a bit of business because of my experience with them and 556 rifles but am now totally soured. The response of "yeah quite a few of our early receiver's have the mag and bolt problem" delivered with an air of nonchalance kinda burned me. Especially since they refused to issue me a call ticket for what is obviously a known problem that slipped their QC on more than just a few if the solution line is commonplace. good luck getting anything else out of me and my friends. sorry to rant but just reaffirming the speculation about the mag/BHO issues.

note: CMMG noted that the way to tell the difference is that the finger shelf on the older lowers (relief cut into the lower) looks like an oval fingerprint indention while the newer lowers will have a square cut. good luck if you have the problem.

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  • 8 years later...

my BRAND NEW out of the box mk.3 (included a pmag from cmmg). WILL NOT CYCLE MORE THAN ONE BULLET. i basically own a bolt action AR. very pissed. and now it seems like everybody and their brother is having the same issue. how the hell has this comapny been around for 20 years with this poop going on? unreal. I i only have  rounds through the gun and i already had to send it back to cmmg. hopefully they fix it. but it seems to me thier lowers are absolutle poop. i knew i shouldve went with aero. damnit 

Edited by nico
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45 minutes ago, nico said:

my BRAND NEW out of the box mk.3 (included a pmag from cmmg). WILL NOT CYCLE MORE THAN ONE BULLET. i basically own a bolt action AR. very pissed. and now it seems like everybody and their brother is having the same issue. how the hell has this comapny been around for 20 years with this poop going on? unreal. I i only have  rounds through the gun and i already had to send it back to cmmg. hopefully they fix it. but it seems to me thier lowers are absolutle poop. i knew i shouldve went with aero. damnit 

Good idea sending it back to them. If they can’t or won’t fix it, let us know and we will do our best to help you get it running for you.

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