UPS dropped off a 16"' 1:7 DPMS upper receiver today that I bought from CMMG.

I grabbed some ammo:
Federal American Eagle 55Gn
Fed XM193 Lot #6
Win Q3131A Lot SH21
Hornady 75Gn OTM
South African M1A3 (1986)

..and went to the local indoor range for a test fire.

I loaded a mag with Federal American Eagle 55GN .223 Rem. Fired one round and had a failure to extract with the rim ripping off the case head, casing still stuck in the chamber.  I have had a bad upper before with that problem, it's usually sign of an oversize gasport or a tight chamber.

So I used a brass cleaning rod to tap the stuck case out and changed ammo to Fed XM193 5.56mm. Fired one round...same problem.

Tapped out the stuck case again and switch to Win Q3131A. Fired 20 rounds without a malfunction, but the case rims were very chewed up.

Switched to South African M1A3 and ran through 30 rounds without a malfunction. Inspected those cases and the rims were less chewed up.

Switched to Horandy OTM, no problem. also fired the remaining Fed Am eagle and XM193 ammo without a problem. Inspected the case rims and they were damaged, but getting less so...

So now I am guessing I have a burr in the chamber or a rough chamber, which is gradually working itself out.  There is still the problem of case rims getting tore up, It's a good thing I dont reload. plus the ejected cases are not even hitting the shell deflector on the upper.

It will take a lot of trouble free rounds before I trust this upper. It also very clear that DPMS didnt test fire this upper!

Thanks for the report

I was all set to pick up some parts from DPMS about 6 months ago.  A couple of friends got some parts that were out of spec,  lower parts and bolts. Also read other reports like yours.

DPMS QC appears to be substandard.

Biggame223

Out

I had the same troubles with a DPMS upper I bought two years ago. It did the same thing you're describing. I sent it back to them, and it turned out to be a head-space issue...Or so they said. I got it back, and the same thing started happening after the second magazine. I cleaned it, and promptly sold it. It seems to me that this is only happening on the uppers that don't have chrome chambers/barrels.

Mine is chrome-lined, chamber and bore. Which means I cant even clean up the chamber with a finishing reamer. Hopefully it will work itself out.

AR15fan,

Sorry to hear your troubles.  I know I've had good luck with my upper so far.  It does sound like an out of spec chamber.

I've read sevaral posts like yours on the DPMS forum which prompted me to do the reliablity test on mine. I've had no malfunctions of any sort yet.

You should give the guys at CMMG a call and see if they can help.  They're good folks and I'm sure they'll stand behind their products.

Keep us posted and let us know how it tuns out.

Take care!

I 2nd Yohimbo.Call CMMG.I'm sure they'll take care of you.If I'm not mistaken, DPMS makes those barrels just for CMMG.

Went back to the range today

Took 3 types of ammo:
Fed XM193 Lot 6
Win Q3131A SH21
SA M1A3 1986

Fired 20 Win, 20 Fed, and 120 M1A3.  No malfunctions, but the brass is still getting chewed up. Found a new problem too, the front sight post is froze. It wouldnt budge. I'll have to try squirting some Liquid-Wrench or Kroil in there before I try to BZO it.

It does appear that the initial failures to extract have worked themselves out.

Sorry to hear of your troubles, AR15fan.  I considered the CMMG DPMS upper myself but wound up getting a Bushmaster 14.5" 1:7 upper when I found they had the barrels in stock.  Just too many questions about the DPMS product for me and I don't mind losing the 1.5" in barrel (it's a carbine, it's [i]supposed[/i] to be short!).

It sounds like the chamber is a bit out of spec and not supporting the case well enough meaning the extractor has to work harder to bring the brass out and thereby chewing up the rim.  I hope it's a burr or the like as you said and can be worked out.  Time will tell.

Yikes!  I am very sorry to hear that!  No really, I AM VERY SORRY TO HEAR THAT!  My 16" 1/7 CMMG/DPMS upper arives on Thursday, heh.  Every review I've seen of these uppers so far have been flawless.  Eating everything that's thrown at it, and one of the most accurate battle-uppers out there.  Yojimbo has one that's just superb.  I'm sure CMMG will take care of you, they seem like great guys and I've heard nothing but great things about them.  Hope your problems get worked out, let us know how it goes!

I will be taking mine out to the range on saturday after I spend thurs/fri stripping, inspecting and lubing it.

Thanks. I would like to give it a chance to "break in."  It hasnt actually had a stoppage since those first two rounds. it's just mangling the brass at this point. Once i can get it out to the desert, and run a couple hundred rounds through it, I'll have a better idea if it's going to be reliebale for me. I'm taking this rifle to Gunsite in the spring, so it needs to run 100%.

your

AR15Fan,

Make sure to get some Wolff extra power extractor springs.  These are just like the Colt extractor springs with the black inserts.

Good luck, and keep us posted on how it's functioning.

I know what you mean by that!! I broke in a COLT 11.5 F/A weapon that did this about once a magazine until it finally started to act right 500 rounds later. I have to vouch for the CMMG/DPMS stuff though. I own one and it is by far my favorite ar15 ever.

Like I mentioned, a QC problem can, and does, happen to any company (remember the bushmaster "overtorque" barrel issues?)Otherwise I would've thrown that COLT away when it started ripping the heads of cartridges, but it has since turned out to be a fine rifle. I wouldn't judge the whole company based on the break in problems of one weapon.

The true test of a good company is how well they stand behind their company. The CMMG guys will make it right, but don't take my word for it.

CMMG & DPMS,
Thank you for your interest (concern).

I took the upper to the range again today.

30 Rnds S-A M1A3 (1986)
10 Rnds Fed XM193 Lot 6
60 Rnds Win Q3131A Unk Lot#

All functioned fine.  Win brass looks good. About 1:3 of the SA brass gets chewed up. In 260 rounds fired total, its only malfunctioned twice...the first two rounds which failed to extract.

When I get my ARMS #40A next week, I'll run another 100 rounds through it. Then I'll get it out to the desert later this month...

[b]UPDATE[/b]

Round count has now exceeded 1000 rounds including Win Q3131A, Fed XM193, SA M1A3 & Horn 75Gn OTM.  Shooting ewas done at a indoor range, outdoor regulated range, and desert plinking. No stoppages of any kind since the first two rounds. This upper is a keeper!

Is the brass still getting chewed up, or is it alright now?

You know what, that's a good question, But I never even thought to inspect of my brass this last time out. I shot 25 Rnds of the Horn 75Gn OTM and 90 Rnds of M1A3 without a hicccup.

My Black Hill 77Gn OTM is supposed to arrive tomorrow. The rifle is still dirty from the last trip, and I'll try the new ammo (and inspect the brass) tomorrow afternoon.

I have two uppers that came from CMMG. One I ordered directly from them, then one that was brand new a friend bought and he needed the cash. SO I bought it from him.
Again, both from CMMG.

I know I will get flamed, but the CMMG uppers I have I like and trust better than my Bushy's and Colts.

I have had 1300 rounds through one of my M4A3 CMMG uppers without cleaning. That's right 1,300 in one day with NO cleaning it. It kept its accuracy and kept firing. Not one hiccup. I also used a wide array of ammo in it.

The other upper is just as good.

I am very sorry for your upper trouble.
I have never dealt with customer service like CMMG's, and frankly their service to their customers is hard to get anywhere else.

If you are having the problem you mention about your upper. CMMG I am sure will go beyond the call to fix your problem.
Please give this upper and CMMG one more chance. I am sure you will be greatly satisfied!
I just had to add my 2¢

I have a CMMG/DPMS upper, I had a huge long thread on getting the entire rifle to work properly.  You've probably seen it.  Now to the important part...

I've saved every single peice of brass (I could find) since getting this upper.  I had numerous problems, including FTEx's and even when I was getting no FTEx's the case rims were still getting chewed up.  Inspecting case rims and primers is one of THE best ways to make sure all the timing is right.  I polished my chamber with Mother's Mag & Aluminum polish (works on more than just that) and that helped.  I didn't get a single FTEx after that that I remember but case rims were still getting chewed.

I suspected an oversized gas port.  So I got a Colt M16 bolt carrier that was heavier and ground back the portion that would contact the autosear.  I also add a Colt "H" buffer.

These two items effectively slowed the action down, recoil was far lessend and case rims were coming out perfect.  There should be NO case rim deformation (only an extractor mark) on all your case rims.  If you're getting ripped rims, but everything is extracting properly, you're operating at the edge of reliability.  My upper was trying to extract before the chamber pressures had subsided and the casing was still squeezed outward against the chamber walls.

I suggest you inspect your case rims CLOSELY (every one) if you want to maximize the reliability of your upper.

If I had to do it all over again, I'd still order this upper - it's a bargain, you simply cannot find the configuration I wanted anywhere else but Colt and we all know how much they charge.  However, I'd leave out the bolt/BC and get the Colt BC/Bolt.  I'd also take the barrel off and re-install it myself, mine came loose by just playing rough with it.  Take care, glad to hear everything is working for the most part.

Edited to add:  I should emphasize that the significance of the Colt BC/B was that it was HEAVIER.  Even with the ground-back auto sear it still had much more material & weight there, it also had a shrouded firing pin (DPMS did not) adding more material & weight.  This helped to slow down the action.

I have a 14.5" CMMG/DPMS barrel that I installed myself.  It has always worked flawlessly.  The bolt & carrier were ordered from CMMG as well.

I typically use SA surplus and fired 200 rounds or so in an hour 2 weeks ago.  The rifle was sighted in using Black Hills 77 grain.  

No hicups, brass is fine.

AR15fan,

Glad to see you're getting it all worked out!

I've had my CMMG 16" 1/7 upper for while now and over my Christmas/New Years vacation my brother and I put 3000 rounds though it, all XM193, with ZERO malfunctions!

I even went to 2000 rounds without cleaning and only a few drops of CLP on the bolt and carrier at the start of each shooting day.   I'm sure it could have went a lot longer but I couldn't take it anymore so I broke down and cleaned it.

I also just checked my shells and have not seen deformation or ripping.  All I can see is a small extractor claw mark.  Since I can't leave things well enough alone, I will probobly test my upper with an H-Buffer and see if it makes it run any smoother.[BD]

BTW, when I got my upper I did not get the bolt and carrier with it.  I had a new spare Armalite bolt and carrier with a Wolff Extra Power Extracter spring installed. So far I've never had a malfunction on this upper.

Though I can't really say whether or not the DPMS bolt and carrier hand anything to do with the issues Wyv3n and you had, it does make you wonder.  I know I was glad I didn't have the DPMS bolt and carrier after Pat Rogers and some others mentioned seeing them break...[:|]

I'd also like to say I would have no problem buying another CMMG upper.  IIRC, CMMG mentioned that they may be gettting the newer ones with the forged front sight bases!  So now they're even better!

I know for a fact that this was the problem.  I did hours upon hours of reading on extraction and action timing alone.  A big help among others was a paper by someone in the military on extractor lift and action timing.  Don't have the link right now, but I might be able to find it.  Not only were the case rims heavily worn, but there were signs of extractor lift as many of the extractor marks did not go deep into the rim.  The shell casing was creating too much resistance.  A stronger spring and the addition of an O-ring would be most peoples "solution" to the problem, however this would lead to prematurely worn extractors.  The real heart of the issue was that the chamber pressures hadn't subsided and I needed to slow down the action to allow chamber pressures to be lower at the time of extraction.  You have to be careful though, if you allow ALL the pressure to go, you'll have the same problems.  A certain amount of that pressure helps to keep the spent casing against the bolt face during extraction.  All of this is detailed in that paper.




If this is an issue you can purchase a forged FSB from Yankee Hill Machine and have it installed for around $35.

I'd like to end with a note that now that all the bugs are worked out of my rifle, it has been flawless.  Close attention was paid and hours upon hours of reading was done on the AR-15 system the whole way through.  I wouldn't hesitate to put my upper against ANY colt upper.

I've litterally dumped rounds caked in dirt through it both in slow fire and bump firing.  I've done it with the rifle completly dry, heavily lubed, in 35F degrees and 105F degrees. Not a single hickup.  I can't get it to NOT function now.

What about the front sight post?

Great post btw and keeping us updated.

W,

Yes, I read the "Extractor Lift" paper when the links were posted here and that's what got me thinking about the H-Buffer.[:D]

I also the agree the cast front sight is an easy fix but it would be nice if you didn't need to![;)]

IMHO, the cast front sight is pretty damn robust and other than a couple members having some anecdotal breakages I've never heard of it being an issue or ever seen one break. I myself prefer the forged front sights but I'm sure the cast ones will work just fine even under heavy use.

Someone needs to do a destruction test on both forged and cast front sight bases and see what what the real difference is!

Anyone have a link to this "Extractor Lift" paper?

Forest,

Heres the link: [url]http://www.dtic.mil/ndia/2003smallarms/index.html[/url]

Scroll down to section "VI" it's listed as "Understanding Extractor Lift in the M16 Family of Weapons by Mr. Frank Dindl".

All the presentations are in PDF or PPT format so hopefully you can read them.

BTW, if you look around there's lot's of good reading on that site![;)]

Outstanding - Thank You Sir!

Agreed.



Castings can vary HEAVILY in quality.  Bad castings are terrible.  Good castings are well.. good.  Not as good as forged of course, which starts off as a cast until it's hammered.  But a good cast part can be very durable.  I've used my cast FSB for leverage, wacked it good with a hammer and on door entry ways, hasn't budged, cracked, bent or anything.  Would I rather have forged?  Of course.  Do I loose sleep at night because mine is a GOOD cast part?  No.



Well, this isn't easy due to the reasons above.  A good cast will hold up pretty well, a bad cast won't stand up to more than a few wacks.  At the point a good cast will break, a forged part generally likes to bend instead.

Yes, tons of good reading.  I found that extractor lift paper extremely helpful.  I thought I had a good understanding of the AR-15 extraction & ejection process before, maybe I did, but now I know more. [:)]

It's pretty common knowledge that too fast an action causes problems.  This paper helps us to understand the dynamics of the problems created by too slow of an action.  Often times, when an action is too slow, people "cure" it with heavy extractor springs and O/D-rings.

I'm of the school of thought that you should work out your rifle's timing as best as possible -- not be too slow, and not be too fast with standard extractor springs and no O/D-rings.  Once the rifle's action is timed right, add the extra power extractor springs and O/D-rings.

I don't like the school of thought of get it as slow as possible.  As soon as any resistance is added (such as extreme temperatures, dirt, running the rifle dry, etc.) to a rifle who's action is just barely getting enough power to cycle as it is will have malfunctions.

I've been considering writing up a paper on getting the timing to the "ideal" level and then posting it here for peer review, maybe I'll do that.