DPMS CMMG PROBLEMS

[the bigness]

Hello I have a cmmg lower with bb and 10/20 magpul mags.After 200 rounds 40 of them bent and mangled today @ the range I realized when I hold the mag up while shooting no feeding problem.This is driving me crazy man.The upper is DPMS

Doesnt Provide Multiple Shots:) Have you guys had any problems with this combo? After spending $3000.00 on magpul everything/jard/enidine/fws30 comp./eotech combo I would like to have a shootin gun not a single shot lookin gun.

What you got? I appreciate any help. Thanx Jim

[Matt.Cross]

Sounds like the problem could potentially be the mags themselves. Are they new? A worn magazine catch is the only reason I can think of why your mag problems go away whenever you shoot with the mag pushed in. Check your mags and your magazine catch for wear that could be problematic. I've also heard of people having problems when their mag catch was one turn too loose.

[the bigness]

I'M USING 10 BRAND NEW P-MAGS (10/20) IN ROTATION

[imschur]

What is a "bb"?

Are you saying that the first 200 rounds were good then the next 40 went to crap or 40 out of 200 bent and it was all a bad experience?

Did you assemble this yourself?

Is it short stroking?

When you get a good run does the bolt lock back properly after the last round?

[98Z5V]

I've also heard of people having problems when their mag catch was one turn too loose.

This part is a big deal on the .308s, because the mag catch parts are all AR-15 spec stuff.  They have to be turned in just right on the .308 (not flush, but not too far from flush with the button), or they'll turn into a problem later - if not a problem from the start.

May not be the exact problem the OP is having, but it's something to check out.  <thumbsup>  I was wondering about the "bb" reference, too.  <dontknow>

[98Z5V]

I'M USING 10 BRAND NEW P-MAGS (10/20) IN ROTATION

10/20 - you using 10-round conversions from some company, but all P-MAGs?  Bent and mangled rounds (feeding problem) can be caused by mag springs that are WAY too strong, but I haven't seen anything like that from a new 20-rd P-MAG so far.  Not even brand new ones, outta the wrapper and loaded at the range.

It can also be from the BCG short-stroking, like imschur asked about.  That's gonna come from a gas problem, or a buffer/buffer spring problem.

[survivalshop]

Try loading the P-mags to the full 20 rounds & letting them set that way for a few days to a week . I had the same problems with my CMMG lower as far as feeding (no mangled rounds ).

The CMMG lower just did not like the P-mags at first until I seasoned the mag springs with a full loading an setting aside for a week .

Mine all function fine now .

The DPMS & C Product mags worked fine .

Look in the Generial section under "16 " barrel with rifle length gas system ".

I have a CMMG lower with a SI Defence ,Gen. II billet upper.

[TacBlade]

survivalshop, can you PM me what your whole setup is?  I am doing the same thing, except not the GEN II upper. Thanks

[the bigness]

BB-bullet button Stupid california compliance thing 10/20- 20 round pmags modified to only hold 10 another calif/compliant....

[the bigness]

The first one goes bang then the second bullet the bcg rides over push toward feed ramps and gets the grind.When holding the mag

while shooting and pushing up slightly full mag dump.Bolt locks back after good run.

[98Z5V]

Ah, I forgot about the bullet button crap you have to deal with.  I'd look there first - at the mag release setup, and how the bullet button is threaded onto the mag release.  If you're able to hold the mag in a position to make it feed accurately/correctly, that's gotta be an indication that the mag release isn't holding it into the proper position (when you're not gripping the mag).  Make sense?  I think I confused myself, trying to explain that...  :o <laughs>

Edit - what's happening to your gun is called "bolt over ride."  Some Google searches on that term should give you some decent results, and maybe how others have solved it.  <thumbsup>

[the bigness]

Thanks for your help I will check bolt over ride threads. I'm goin out to the range in a few.I converted a siaga 308 to AK platform and this thing shoots any ammo all the time bone dry.I can see why all these hard core survival guys have a back up AK just in case

they are crude but they seem to work 100% of the time.So if I fight this AR and it gives me grief this fire breathing AK308 should keep me from going into AR depression mode.

[survivalshop]

Yes , the bullet button could need some tweeking to get the mag high enough or stable enough to feed reliably.

Might also look deeper in to your mag conversion .( 10/20 )

[the bigness]

Well back from the range w/dpms.cmmg 308 and after shooting radway green 762 and british delinked ammo (both NATO) NOT ONE MIS FEED BUT I'M STILL HOLDIN ON TO THE MAG LIKE A GRIP POD!(have to push mag up for for the other 9). The AK308 which I found is discontinued ran without a hitch,as I new it would.

Funny thing happened @ the range today.My back was turned to the targets 100/200/300/400/5/6 and I hear the range master

call a cease fire.He said animal on the range! I turned around waiting to see a squirrel or on the outside a raccoon but no, to everyone's surprise it was F@%$^*#  3 deer one buck and two smaller! Now to  a lot of folks this is probably an everyday scene but being 35 min. from LA is pretty wild,for wild life.I hope someone caught video. Walking @ 300yrd mark Now I want to shoot animals. The  fine would be poaching/felony/$10,000 dollar fine California is a great place to live but ya wouldn't want to shoot here. Oh yeah I LOVE ANIMALS AND BAMBI BUT IF THEIR  STUPID ENOUGH TO WALK THROUGH A RANGE W.50BMG AND A GRIP OF SHOOTERS THEY WILL DIE AND I WILL EAT THEM!http://308ar.com/forum/Smileys/default/grin.gif

[survivalshop]

That pretty much shows its a mag or how the mag is attached to the rifle, problem.

[the bigness]

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]

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]

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]

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.  <dontknow>

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

[the bigness]

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]

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]

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]

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]

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

[edgecrusher]

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