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cbvanb

DPMS ejection issue UPDATED

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Greetings, all. I've been enjoying the site for a long time now, and for my first post I need help with an ejection problem. I have a DPMS LR308 AP4 that until yesterday ran flawlessly, although with a bit of a twist. In close to 600 rounds through the rifle the empty cases have never hit the shell deflector upon ejection. It appears that the base of the base is slammed into the rear of the ejection port, bounces off the front of the ejection port, and then clears the rifle. The attached photo shows the witness marks on the ejection port from the ejected empties. Yesterday I had an empty round hang up in the ejection port, during a competition of course. I can't say for certain that malfunction was caused by the peculiar ejection of this rifle, but this has bothered me for awhile now and I thought I'd seek some input. Any ideas on what causes this ejection issue, and what to do about it?

post-1347-136297274049_thumb.jpg

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The rims appear normal. There is always a dent about mid case which I assume comes from the front or back of the ejection port. I'm close to 600 rounds through the rifle. I run the bolt very wet, using Mobil 1 for a lubricant. I'm currently using either DAG German surplus or Federal American Eagle ammunition.

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Having marks on or near the ejection port is nothing to worry about , they are hitting the brass deflector ,just not leaving a mark, yet.

I would look into the extractor for burr's or weak spring or some thing may have gotten into that area , also check the ejector & make sure its free to move with out hanging up .

It looks like the fired case is late being ejected .( dent in mid section of case, not unusual )

Where are your ejected cases landing ?

What buffer & spring are your using , std DPMS ?

How are the spring tensions for the extractor & ejector ? easy , heavy ?

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The cases tend to land about three feet to the right and front of my shooting position. It' s very consistent in that regard. Everything is standard DPMS at this point. I"m going to take the bolt apart and look for anything unusual.

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What Survival said ....

"Having marks on or near the ejection port is nothing to worry about , they are hitting the brass deflector ,just not leaving a mark, yet.

I would look into the extractor for burr's or weak spring or some thing may have gotten into that area , also check the ejector & make sure its free to move with out hanging up .

It looks like the fired case is late being ejected .( dent in mid section of case, not unusual ) "

Not to get off topic,but how is the Dag treating your barrel?

Ive only shot bout 20 rounds of it...seems fairly nice!

Wash

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There don't seem to be any issues with the DAG that I can see, with about 200 rounds downrange. It is so unbelievably accurate that I ended up buying several thousand rounds. I have noticed that it burns a little dirty, and after 3 or 4 mags there is a gritty residue in the upper. It hasn't caused any issues so far, given that I run the bolt carrier really wet.

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I have shot 200 rounds(of the DAG) with no problems but it has left the BCG and inside of the barrel dirty. I've got 200 rounds left in a sealed pack and will be saving that for a while.

Also if the mark being left on the casing is coming from the upper reciever you could grind the offending spot away. If it is being caused by the ejector you might have to live with it or change the ejector spring.

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cbvanb,

Thanks for bring up his topic. I have recently built a ar308 and have had ejection problems. My casing are dented at the top. I shoot a few rounds off and the bolt do not go all the way forward. I have noticed that the bolt is 1/2" from clearing out of the way of the ejection port. I was told to try a CAR-10. I have also been soaking the bolt parts in Mobil 1.

Do you think that the shells are hitting the bolt.

                                          Zuma Bob

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OK, did a little research at the range today and here's what I found. The empties are not hitting the shell deflector. I tested this by putting a piece of tape over the shell deflector. As you can see in the photo, after 30 rounds the tape hasn't been hit. I had my shooting partner fire the rifle while I watched, and after examining the spent casings it appears that the shell is coming out of the ejection port in a straight line, and the rear of the case is hitting the back end of the ejection port, then bouncing almost straight forward. I examined all 50 empties and they had an identical mark on the rear of the case, on the rim. The ejector spring is so stiff I can barely push it back into the bolt. There doesn't appear to be anything wrong with the extractor, but at this point I'm going to change it out to see what happens. I can't think of any other explanation for this ejection issue.

post-1347-136297274529_thumb.jpg

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I wonder if this is what Slash from heavy buffers is refering to with DPMS buffer and buffer spring inconsistancies and short lives?

Is this a factory rifle? Is the result the same with all ammo?

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Factory built AP4. I wondered if it had something to do with the bolt velocity on ejection, but I can't seem to find any other information about it on the web. I had hoped someone here would be familiar with the issue. This rifle does this with all ammunition I've tried. My other DPMS LR308 ejects normally.

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is your other a carbine? If so switch the buffer and buffer spring and test again.

AR15.com has this chart for AR-15 ejection. I think it will apply here as well

ARejectionpattern.jpg

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Thanks for that chart. My other 308 is rifle length, unfortunately. I sent an email to Clint describing the situation, I'll post his response. It may have something to do with bolt velocity. I've noticed if I hand cycle live ammo through the rifle it seems to eject correctly.

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Had the same issue with my DPMS 308 producing good dents at the mid-section on cases and landing in the 2 to 4 o'clock position. I didn’t like the banged up cases since I was reloading.  The stock rifle is over-gassed so I added an adjustable gas block (JP rifles) and opened it up from essentially closed at ¼ turn or so intervals until I found good extraction (with only very slight marks) and then gave it another ¼ turn.  Put some loctite on it and that was a couple years/1000+ rds ago and it has been working like a champ.

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cbvanb,

When you pull back the charge handle is the ejection port clear of the bolt? I have put the right buffer and spring in my gun and they said it was probably the problem. I well let you know what happens.

                                                Bob

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Just checked that issue, the bolt is completely past the ejection port. I spent all weekend researching this and I think it does come down to the gun being over gassed. So the options are:1.heavy buffer:2.adjustable gas block:3. replace collapsible stock with fixed stock. I'm leaning towards the heavy buffer, but want to wait for a response from Slash regarding a couple questions I have. I'll keep the thread updated.

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cbvanb

I was at he show yesterday with my gun. My 308 guys (Sal and Luis) got me set up. Got a new buffer and a spring. They are confident that its going to work. Nofail has been telling me this for a while. From what I've heard Slash is the buffer and spring guy. I am going to shoot mine tomorrow. I well let you know how it goes . I well be talking to Slash sooner or later. Wish me luck.

                                              Bob

                                     

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Hopefully your problem is solved. I got an email from Clint yesterday, he wasn't a hundred percent certain his buffer would solve my problem but he is convinced all the carbine style 308 rifles are overgassed. I ordered his buffer and spring, should have it here by the end of the week. As soon as it arrives I'm headed to the range, will update when that happens.

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I dug up a picture of the dents on my cases before and after using the gas block.  Some of the dents were really bad before I added the adjustable block; I have an 18” barrel on my DPMS.  The scratches on the neck were due to sharp edges on the barrel extension locking lugs (there is another thread here somewhere that discusses that issue).

308casedents.jpg

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cbvanb,

Took the 308 out today and it worked near perfect. Shoot 40 rounds. No jams but by the ejection graph the shells are 1:00 to 3:00. Not @ 3:00 to 4:30. Sending the hand rail out tomorrow. I well deal with the buffer and spring later. I'm curious to hear how your spring and buffer goes. Good luck.

                                    Bob

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Just an fyi, my 308b with 18" barrel has no shell deflector or dust cover.  About 1/2" behind the open port there is evidence that the shells are actually bouncing off the side of the upper receiver but does eject just as the chart shows it should: between 3:00 & 4:30, without the deflector.  My rifle as an A2 stock and standard buffer and spring.

Rome

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SUCCESS! Installed the Slash heavy buffer and spring this morning, ran 40 flawless rounds through the rifle this afternoon. Ejection is now around 3:30, and it's clear the rounds are striking the middle of the shell deflector on the upper. Cases show no denting. I believe the problem is solved. The spring provided by Slash is a couple coils longer than the standard carbine spring, and I think I'm going to try the heavy buffer with the standard factory spring just to see what happens, but I feel much better about the way this rifle runs now. Thanks for all the input.

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