Topic: DPMS CMMG PROBLEMS (Read 3377 times)

the bigness · « **Reply #15 on:** September 03, 2010, 12:50:11 AM »

Well Eric from CMMG just e mailed and I'm going to send it to him. Hopefully they can get it going. I want to thank all of you for your input. I will post the results when I get it back. Thank you.

Brassjunkie · « **Reply #16 on:** March 27, 2011, 09:29:08 PM »

Well I'm a little late in jumping in on this post so here goes....CMMG lower with endine buffer, AP4 16" upper and Magpul mags. I get bolt overrun with the Magpul mags, but the DPMS 19 rounders work fine......Changed to a Sundevil lower and same problem, bolt overrun. I called Magpul and they sent a new mag....same problem, bolt overrun. In looking at the DPMS bolt face, it appears the bolt lugs are beveled on the front side which may contribute to not picking the round up and therefore sliding over it. It appears the small difference in mag lip thickness may just be enough to not pick up the round....I would like to try a different bolt that has a better lug contact surface. Does anyone out there using magpul mags experience this and or have a solution to overcome this problem?

the bigness · « **Reply #17 on:** March 28, 2011, 11:52:43 PM »

I got pissed off with the whole thing bought an x box and started playing black ops. Th game would at least friggin shoot. If you hold magpul mag up does it fire? i have yet to send my rifle to cmmg. If it is the bolt I will follow suit. Please let me know.

survivalshop · « **Reply #18 on:** March 29, 2011, 06:37:12 AM »

Maybe we should find another bolt manufacturer & see if they make there bolt the same way .
I just don't use Magpuls in my CMMG lower & have stopped having problems .
I noticed something the other day on a preban Olympic Arms AR15 lower I'm using for my 300BLK upper . With the Oly. lower the Pmag is difficult to insert & lock on the mag catch. I had the same problem with bolt over as my CMMG 308 . I switched to normal GI mags & she runs like a top.

I do not think these manufacturers had Magpuls in mind when the designed them .The Pmag types work fine in my DPMS 308 lower & my newer AR 15's, so I don't think its not an isolated problem with the plastic mags .

Hell, it took me quite a while to figure out how to get the Bolt stop to work on my CMMG lower.

I also found that if you preload the 308 Pmag with twenty rounds for a week or just keep them loaded , they work most of the time in the CMMG lower.

When I finnish this 300blk build ,I will dig deeper into the PMag 308 problems.

the bigness · « **Reply #19 on:** April 01, 2011, 12:06:13 AM »

Ya kinda lost me do your pmags work with cmmg ? As far as bolts go jp enterprises jpeb-308 is one that will work on our platform,but a little pricey.

survivalshop · « **Reply #20 on:** April 01, 2011, 09:02:26 AM »

My CMMG 308 lower has had problems with the Magpul LR 308 mags since I started using them . I have no problems with DPMS or Cproducts mags at all . They function flawlessly.

The Pmags have bolt over problems ,which cause the bolt carrier to half strip the round of the mag some times & its a bent cartridge every time it does it .

I'm not using the Pmags in my CMMG lowered 308 any more until I find out what is going on .

My DPMS lowered 308 likes any of the mags I use ,with no problems .

the bigness · « **Reply #21 on:** April 01, 2011, 11:51:56 PM »

Yeah prior to the large cap mag ban I bought a glock 10 mil and only bought 2 mags. So now I buy 10 at a time. The dpms mags were
from the batch that wouldn't work. So now I have 20 mags that don't work 10 dpms and 10 pmags! As I mentioned before if I push up on the pmags it functions,if not the bolt rides over and beats the sh-t out of the round.

survivalshop · « **Reply #22 on:** April 07, 2011, 09:12:17 AM »

DPMS will take the mags back & fix or swap them out ,if you call them .
You can sell the Pmags here if you want . I have not had a problem with Cproducts mags in ether of my 308 rifles .

Holding them up & they work ? Almost sounds like the mag catch is too loose .
Mine lock in OK ,but I have not yet had time to really look at why the bolt is going over with the Pmags in the CMMG lower.

Going to do some measuring between the two lowers this weekend ,if I don't have to work.

the bigness · « **Reply #23 on:** April 08, 2011, 12:00:24 AM »

Cool let me know what you come up with.In the mean time I will check out cproducts

edgecrusher · « **Reply #24 on:** April 08, 2011, 02:08:45 AM »

I have some of the c products mags and they work well in all the versions I bought. 7.62x51 larue/pws, 7.62x39 preban colt sporter

98Z5V · « **Reply #25 on:** April 10, 2011, 01:10:43 AM »

I don't think it's necessarily a mag problem, but a machining problem with the uppers. Or lowers. Height-over-bore kinda thing. Uppers are being machined with the bolt carrier circumference too high, over the top of the mag, or the lower-to-upper stack height is being machined too high.

There's no standard to follow for machining these rifles. Nobody follows a "set" set of plans during machining. When we combine different uppers and lowers, the true flaws come out.

With guns having bolt over run problems in .308, that's the first thing I think of. Different uppers and lowers combined, and the machining differences between the two companies isn't even compatible - because they're all doing what they want to do.

What upper does CMMG recommend using? Does that upper run with Pmags? Now, I'm not defending Pmags here, I'm just trying to think of ideas that might lead to the real issue. There are so many guns that Pmags run perfectly fine in - mostly uppers and lowers from teh same company, though.

Just a thought...

survivalshop · « **Reply #26 on:** April 10, 2011, 08:26:23 PM »

I think your spot on about the dissimilarities in manufacturing.

I never thought it was a Magpul mag issue & was thinking it was in the lower ,now it may be the upper compatibility issue ,as you say.

I will switch uppers next time I shoot & use my DPMS upper on the CMMG & see how that goes .

I have an SI Defence upper with it now . I'm still going to measure all spec's on the lower, & upper also.
Ya know if the mags work with a DPMS upper , I will have an SI Defence upper to start a new build .
How do they say it , a silver lining in every thing .

the bigness · « **Reply #27 on:** April 12, 2011, 12:11:46 AM »

My problem w/bolt ride over is w/ p mag/DPMS upper/CMMG lower and Calif. legal bullet button which may be the entire problem.

survivalshop · « **Reply #28 on:** April 12, 2011, 06:42:20 AM »

Quote from: the bigness on April 12, 2011, 12:11:46 AM

My problem w/bolt ride over is w/ p mag/DPMS upper/CMMG lower and Calif. legal bullet button which may be the entire problem.

I see a lot of rifles with that bullet button ,that have feeding problems . Wish I knew some thing about that contraption. I guess I will have to look into it .
So , my problem with my CMMG lower may be a different beast, good I'm up for the challenge .

Ya never know , me finding some thing about my CMMG ,could help you with yours.

survivalshop · « **Reply #29 on:** April 13, 2011, 08:23:15 AM »

I looked into that "bullet Button " & I can see no problem with its function , since you are using the normal mag catch .
The only thing I can see that could be a problem is spring pressure on the catch , but that could also happen with the stock set up .

I need to look into the receivers & there specs'