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View Full Version : New M4 CMMG failure to eject


SonicDonkey
10-13-2009, 9:25 AM
I got my OOL rifle back in November and finally got out to the range only to find that the spent cartridge will not eject. The first round fired, bolt came back and tried to load the next but ended up sending the new round into the back of the empty case. After much dificulty removing the jamed round and droping the mag it was still a pain to remove the empty case. I found that if I released the bolt about 1/2" from closed it was enough to engage the extractor on the back of the case but I had to pull as hard as I could on the charge handle to get the case out of the chamber.

Once removed, I loaded one round thru the ejection port, released the bolt, fired, FTE again. I repeated the close bolt release and again, pulling hard on the charging handle was able to get the case out of the chamber. I shot a few more rounds this way, keeping the empty cases as they came out and noticed that they have scuff marks on each side of the case. I ran about 20-30 rounds total this way, trying different ammo also, all rounds were FTE.
Ammo used was PMC223 and Winchester 5.56 both brass case.

Looking for advice or ideas as to what to check or do to fix this issue.

Thanks!

SixPointEight
10-13-2009, 9:32 AM
I'm no expert. But I'd say to clean the **** out of it first. And try again. If you're thinking there might be burrs in the chamber(I don't see why unless it was really abused) you could run a q-tip around in there and see if any cotton sticks anywhere. If it does then you might have burrs in the chamber

southsti
10-13-2009, 9:40 AM
Sounds odd for a new rifle to have a round jam like that, did you lube the rifle up properly when first firing it? I would clean it very well and put a light coat of CLP and go out and test it again. If the problem continues you should take some pictures to help people see whats actually happening and help with diagnosing the problem.

That happened on my rifle once when I was using Romanian rounds, I took it home and cleaned her up and no longer used those rounds anymore, and I haven't had anymore issues. The rounds you listed I have never had any issues with though.

missiontrails
10-13-2009, 10:02 AM
Factory rifle, or home build? What kind of BCG?

Eckolaker
10-13-2009, 10:13 AM
I suspect the extractor spring could be loose, or haver a little play in it. Scuff marks on the case suggest the extractor is not grabbing the case properly and is sliding off after the round is fired.

Also, make sure the damn thing is clean, although a new rifle really should not need a cleaning after 40 rounds.

SonicDonkey
10-13-2009, 10:27 AM
I bet you were using wolf ammo despite the statement of PMC and Winchester, in any case,
1. Clean throughout
2. Lube throughout including buffer spring
3. Check for proper clearance of bolt over Hammer, some hammers are out of spec and my partially bind the bolt, if the bolt does not move smoothly and freely without any noticeable friction/binding of hammer, replace hammer.
4.Scuff marks means you have burrs in the barrel, I doubt that is in part of CMMG inspection- because they are extremely meticulous in their inspection/testing process- probably prior use of other ammo????QUOTE]

While I was ready to order a metric S*$T ton of Wolf before I got the rifle but then I decided not to after reading their warranty and ammo warning. I only have brass case ammo. The ammo I took with me was the PMC223 and bought the Winchester at the range to make sure it wasnt an ammo issue, same results with both.

I did fail to clean the rifle out of the box but after a few strips to familirize myself before firing for the first time I did not notice any excessive assembly lube or lack there of for that matter. Im no expert and new the the AR rifle but it didnt look like it needed attention before first fire. My bad if it should have had a good scrub.

Do you recommend using the sandpaper on a chromed lined barrel?

[QUOTE=missiontrails;3204999]Factory rifle, or home build? What kind of BCG?

This a 100% CMMG shipped assembled rifle.

jchen76@gmail.com
10-13-2009, 10:31 AM
Had an AR that did that with Wolf ammo. Brought it to gunsmith to knock out the stuck case. He recommend that I chamfer and polish the chamber, possibly with fine steel wool.

missiontrails
10-13-2009, 10:34 AM
[QUOTE=Massafeff;3204929]I bet you were using wolf ammo despite the statement of PMC and Winchester, in any case,
1. Clean throughout
2. Lube throughout including buffer spring
3. Check for proper clearance of bolt over Hammer, some hammers are out of spec and my partially bind the bolt, if the bolt does not move smoothly and freely without any noticeable friction/binding of hammer, replace hammer.
4.Scuff marks means you have burrs in the barrel, I doubt that is in part of CMMG inspection- because they are extremely meticulous in their inspection/testing process- probably prior use of other ammo????QUOTE]

While I was ready to order a metric S*$T ton of Wolf before I got the rifle but then I decided not to after reading their warranty and ammo warning. I only have brass case ammo. The ammo I took with me was the PMC223 and bought the Winchester at the range to make sure it wasnt an ammo issue, same results with both.

I did fail to clean the rifle out of the box but after a few strips to familirize myself before firing for the first time I did not notice any excessive assembly lube or lack there of for that matter. Im no expert and new the the AR rifle but it didnt look like it needed attention before first fire. My bad if it should have had a good scrub.

Do you recommend using the sandpaper on a chromed lined barrel?



This a 100% CMMG shipped assembled rifle.

In that case, you need to send an e-mail to CMMG technical support, Greg will answer fast. They might need to inspect your bolt. My CMMG SA BCG ejects like a beast, and throws the shells all in about the same place.

missiontrails
10-13-2009, 10:40 AM
Also, using a heavier buffer will delay extraction a fraction of a second, which sometimes aids ejection in times like this, because it allows the ejector tooth to get a better bite on the casing. I run a 5.2oz 9mm buffer in my CMMG M4 14.5". I think these rifles have slightly larger than .063 gas ports, which classifies them as "over-gased."

SonicDonkey
10-13-2009, 10:45 AM
[QUOTE=SonicDonkey;3205135]

In that case, you need to send an e-mail to CMMG technical support, Greg will answer fast. They might need to inspect your bolt. My CMMG SA BCG ejects like a beast, and throws the shells all in about the same place.

Email sent, will see.

Vanguard
10-13-2009, 10:48 AM
Yes, your best best would be contacting CMMG. They are probably familiar with any problems that their rifles have had in the past and will know exactly what it is. I'm sure they'll help you out and take care of the problem for you.

missiontrails
10-13-2009, 10:49 AM
[QUOTE=missiontrails;3205163]

Email sent, will see.

Oops, not Greg, I meant Garson.

IsaacGlass
10-13-2009, 11:06 AM
Would be interested to know if this a factory built or a DIY deal? Is the BCG stake? if it is a factory build, CMMG could have used the wrong buffer.
FYI...I and many others shoot Wolf ammo through my Stag factory build with no problems whatsoever.

missiontrails
10-13-2009, 11:59 AM
Would be interested to know if this a factory built or a DIY deal? Is the BCG stake? if it is a factory build, CMMG could have used the wrong buffer.
FYI...I and many others shoot Wolf ammo through my Stag factory build with no problems whatsoever.
Definatelly not a staking issue, OP said that a new round is being scooped and chambered into the non-extracted round that is still in there.

SonicDonkey
10-13-2009, 12:47 PM
CMMG got right back to me via phone however I missed the call and when I got the voice message the power went out here. It took land, cell, and data service with it too! Back on now though, obviously.

We will see if I can get back with them before they close today, will probably have to followup with them tomorrow.

UPDATE:

CMMG did get back to me and advised I polish the chamber with some polishing compound and a chamber brush. Will advise on results.

Loner
10-13-2009, 5:07 PM
I had the same problem on a Sabre Barrel on a parts build. Randall(ar15barrels) polished out the chamber, that and a H buffer fixed the problem.

mls343
10-13-2009, 5:23 PM
Check the bullet button. You will notice that on the bullet plunger that it is threaded. If this comes loose, which it does with regularity, it can cause your magazine to not fit properly in the mag well. Just take a small screw driver and quickly tighten it if it loose.

Do everything that is stated above first, but just in case, give this a quick check.

Good luck.

till44
10-13-2009, 5:39 PM
CMMG custoomer service is great. Send them an email and they'll send you a prepaid UPS shipping label for free. They take care of their customers.

Nix78
10-13-2009, 6:15 PM
Yea I think mine is going to do the same , The extractor spring on mine is not strong at all I went through mine before I'll shoot it ....I might be in the same boat.

SonicDonkey
10-14-2009, 8:50 AM
I ran the chamber brush thru the chamber with the polishing compound on it a few times as recommended by CMMG and it definatly improved on the ease of removal of the round.
To test I would do the following since I havent been back to the range yet
-Upper off lower and bolt out, drop a round in the chamber install charge
handle and bolt and fully close.
-pull charge handle to remove round.

As mentioned, when first firing it was all I could do puling on the charge handle to remove the spent case, now it is quite a bit easier but still has some resistance. I need to get out the range to test live function though.

And as others have mentioned, CMMG customer service is VERY helpfull.

SonicDonkey
10-19-2009, 3:28 PM
Well, I tried to work the chamber as directed by CMMG with little success. I did manage to get a few auto ejections with only a single round in the mag but when the mag had more than one round in it it would not eject and jam. So at this point I have a difficult to load single fire black rifle...:(

The upper and barrel shipped back to them today, now the wait begins.

technique
10-19-2009, 3:32 PM
Sounds like it may have been a magazine issue...Too much spring tension. May I ask what kind of mag you were using? And did you try more than 1 type?

SonicDonkey
10-20-2009, 9:30 AM
Sounds like it may have been a magazine issue...Too much spring tension. May I ask what kind of mag you were using? And did you try more than 1 type?


Cant remember the name of the mags right now, but I did use a few different mags. Even one from a friends rifle that was working just fine.

ar15barrels
10-20-2009, 8:53 PM
This gun sounds like it has a carbine gas system and a rough chamber.
Hone (not polish) the chamber, put a heavy buffer in it and upgrade the extractor spring.

SonicDonkey
11-03-2009, 8:57 AM
The barrel went back to CMMG and just came back last week. No specifics were given, they just said it had a bad chamber. They replaced the barrel, checked headspace and test fired.

I must say that CMMG handled it as good as could be expected.
Thank you CMMG!!

ponderosa
11-03-2009, 9:23 AM
Cool deal, how's it shoot now?

troysland
11-03-2009, 10:02 AM
I had the same problem with a no name upper. I bought an overpriced chamber brush at Turners ($6) and went to town on it. Whatever burrs existed are no longer holding the case after firing, so no more FTE.