Ejection pattern concerns

[MDavis]

Gentlemen, 

Thank you all for the knowledge I have received from this group. With your help, I have gotten my rifle to the point where I feel I only have minor tuning left. I read/stalked your topics throughout my 308 build and have recently joined to ask about the ejection pattern. It is a 5D Tactical lower with an Aero upper. The barrel is a Wilson Combat 16" with an "intermediate" gas tube. Aero bolt. I had many issues with cycling and feeding to begin with but have corrected them. I could not find a Wilson Combat BCG in stock so purchased a Brownells BCG that was not headspaced with the Wilson barrel, according to Foster guages. It would close on the NGo but not the Field. I fired the rifle with that bolt and had to mortar the cases. I then purchased an Aero Precision (i think they are made by Toolcraft) bolt and the headspace is correct. The barrel came with a .075 gas port, it is now .093 and I have installed a SLR adjustable gas block. It has a Springco orange and an Odin buffer, in  its heaviest configuration. 4.35 oz. 

When I first fired the weapon with the above configuration, the gas block was set to the highest gas setting, 15 clicks out. The cases of Winchester Match 168 gr Sierra Matchkings landed approx 6' to my 2 o'clock. One click down put them in the same direction but 5', another click in... 4', these were single shot and it locked the bolt to the rear each time. I then went back to the max settings and it cycled through the magazine. On the second magazine it had one malfunction half way through, the empty brass was stovepiped above the round that was attempting to feed. I cleared it and it ran the rest of the second magazine. I think the spent brass hit the deflector block and flipped back into the ejection port. The bolt has double springs and double O rings.

Is it unrealistic to wish for the 5 o'clock, 10' rainbow of ejected brass that I get from ar15s?  Any help or consideration would be valued, the stoppage I cleared rattled my confidence in the rifle and I fear that every spent case is on the verge of causing another stoppage. I will attach some pictures that may be helpful to those of you with experience. 

[edgecrusher]

Congrats on working it out! No, not too much to ask. These rifles will need and extensive break in, so I would say eventually you can turn your gas down and get that. Right not it’s hitting the deflector so hard your getting 2 o clock. A little less gas and it’ll happen but honestly it doesn’t matter that much. 

[shooterrex]

A heavier buffer in the 5 and a half oz range might help.

[MDavis]

Thanks for your response. I have saw your posts in the past and thank you for reading my question. I am pleased with the build, mostly, I have learned alot about ar 308s. I still don't understand why the extractor has to have double springs and double o rings. What will happen if I remove an o ring or the small inner spring? Is there something I can polish? What would a heavier buffer do, or lighter? JP extractor? Different ejector? Remove some metal from the deflector block? I just want the spent cases to kindly get tf away from my ejection port. haha. 

[MDavis]

Thanks to both of you for your time and consideration. I just ordered a heavier buffer from Kaw Valley. We shall see...

[shooterrex]

The heavier buffer slows the BCG group down just a bit. Slower BCG it's not throwing the brass in the same place. This also gives you magazine just a bit more time to raise the next round. As long as the extractor is pulling the brass out of the chamber I wouldn't mess with things.

[98Z5V]

12 hours ago, MDavis said:

It has a Springco orange and an Odin buffer, in  its heaviest configuration. 4.35 oz. 

When I first fired the weapon with the above configuration, the gas block was set to the highest gas setting, 15 clicks out. The cases of Winchester Match 168 gr Sierra Matchkings landed approx 6' to my 2 o'clock. One click down put them in the same direction but 5', another click in... 4', these were single shot and it locked the bolt to the rear each time. I then went back to the max settings and it cycled through the magazine.

 

8 hours ago, shooterrex said:

A heavier buffer in the 5 and a half oz range might help.

^^^  Yep, you change ejection pattern with buffer weight, not gas pressure. 

[MDavis]

Sir, I have read many of your responses on here. I joined this group because of the class I witnessed among members. I did many things to this rifle as a result of knowledge from this forum. Sprinco orange, .093 gas port, adjustable block.. these things have gotten me to this point. I have a great firing weapon and now only have one small concern with ejection angle.  I regret the mistake of thinking this 4.35oz buffer would be heavy enough. I knew you always say 5.5oz buffers. I am somewhat aware of the impact of buffer weight on the cycle of operation, I have used this to tune the .300BOs in the past. 

I will definitely follow up after I receive and fire the rifle with the buffer I have ordered from Wing Tactical. 

[MDavis]

Gentlemen, 

I am sorry to say that the 5.6 oz buffer did not correct my brass ejection problems. I also had another stoppage from the brass flipping back into the ejection port after hitting the deflector. My next idea it to take out one of the o-rings on the extractor. Idk. 

I have another idea of something that is bothering the cycle of the rifle. The buffer retainer pin hammers on the buffer face. This has me thinking that the upper receiver that I have isnt compatible with my lower.  AeroP upper and 5DTactical lower. 

I am aggravated with it, yall tell me what to try and I will do it. thanks for helping me. 

[98Z5V]

6 hours ago, MDavis said:

I have another idea of something that is bothering the cycle of the rifle. The buffer retainer pin hammers on the buffer face. This has me thinking that the upper receiver that I have isnt compatible with my lower.  AeroP upper and 5DTactical lower.

Pics of this.  Post them. 

I can tell you what the problem is, and the solution is - but the solution was discontinued several years ago.

Post pics of the buffer damage.

[98Z5V]

6 hours ago, MDavis said:

This has me thinking that the upper receiver that I have isnt compatible with my lower.  AeroP upper and 5DTactical lower.

There's something wrong with your 80% lower receiver, and not the Aero Precision M5 upper receiver, here...  I don't have chewed up buffer faces with my AP M5s - and I can tell you this before seeing any pics that you can provide - with any of my Aero M5 upper and lowers.  And I have a pile of those.

I HAVE had issues with chewed up buffer faces, on custom billet receivers from a very reputable company.  I solved that with a product that is no longer in production, and that was the Tubb Carrier Weight System. 

I can tell you exactly what the cause of this problem is, and I can also tell you it's not from the Aero Precision M5 uper receiver dimensions.  It's your 5D Tactical lower, only.

Post pics of the buffer, for confirmation.

[MDavis]

 Thank you for your consideration and help. I agree with your assessment. I have confidence in the AP parts, not the 80% part. I have used the 5D on ar-15s with success and was naturally hoping it would be the same with the 308. The 5d site even mentions that it is compatible with the AP: "Our lowers will work with ANY DPMS Gen 1 pattern upper receiver, like Aero Precision or CMMG. It will not work with other patterns, such as the KAC SR-25, or the PSA PA-10". If the buffer striking the retainer was my only issue, I would delete the retainer, though I know that is only a band aid. I fear, and ask you, if this tolerance issue is also contributing to the ejection pattern and ultimately the cycle of operation. The only stoppages it has had is when the spent case bounces back into the ejection port. This build was not meant to be a "budget" minded rifle. I will do what it takes to have a reliable battle rifle that I trust to not let me down. If you say to trash the 80% lower, it will be replaced. 

[jtallen83]

36 minutes ago, MDavis said:

 

There is an offset retainer that may solve that issue, 

https://gallowayprecision.com/offset-buffer-retainer-for-AR-15-rifles

[98Z5V]

11 hours ago, jtallen83 said:

There is an offset retainer that may solve that issue, 

https://gallowayprecision.com/offset-buffer-retainer-for-AR-15-rifles

^^^   That's the answer.  Right there.

The issue is that the tail of the BCG body is NOT pushing the buffer off the retainer, when you close the receivers and pin that takedown pin.  There's a gap between the tail of the BCG body and the face of the buffer when the receivers are pinned and closed.

That offset buffer retaining pin that JT listed will allow the buffer to come farther forward - and the BCG tail WILL push the buffer face off it, and keep it off it. 

Machining tolerances that are off, is the only cause of this.  It can be the upper, or the lower, and I only called that lower because I have enough AP M5 uppers (and lowers) to state that it's not a problem, at all, in those sets.  Only reason I said that.

On functioning, I don't think that's the issue with function, and malfunctions - unless bolt bounce is the direct reason for your malfunctions.  The situation that you have will definiitely cause bolt bounce.  Only way to find out is fix the issue that you have, and fire that thing up and see what happens.  Your buffer won't get chewed up anymore, though. 

[MDavis]

I appreciate the link, I ordered the offset retainer. 

Since the buffer is resting on the retainer and not against the BC that would mean that the beginning of the ejection cycle is getting a huge initial hit, even though it is just a few thousandths. 

I swear that the pivot and takedown pins are perfectly aligned. This weapon has been a very educational process. I assume most of you have already experienced these issues with these builds. 

Today I will take the buffer retainer out and fire it. 

[mrmackc]

Right on Mr Davis!.... have you been taking some of them 308Ar.com smart pills too? They have kinda started looking like rabbit pellets.....to me.

[98Z5V]

14 hours ago, MDavis said:

I appreciate the link, I ordered the offset retainer. 

Since the buffer is resting on the retainer and not against the BC that would mean that the beginning of the ejection cycle is getting a huge initial hit, even though it is just a few thousandths.

Not only is it taking a huge initial hit - the buffer is letting off, right at the very end - when it need to close the BCG.  Again - you nailed it - it's only a few thou - but it's a HUGE issue.  That buffer hits the pin, and that buffer doesn't drive that BCG home, seated.  That's when bolt bounce will DEFINITELY happen. 

Not sure it that's the reasons for your malfunctions, again - but you have to rule that out before you move any further forward with diagnosing the gun. 

You're on the right track, shoot that thing with the offset retainer, and we'll figure out what's happening after that. 

[mrmackc]

Anyone tried to modify the faulty acting retainer pin with a Dremel tool? After checking the one in my LR308 I reckon maybe that might not work too good. Gimme me another bottle of them Smart Pills.

[MDavis]

Gentlemen, 

Much thanks for working me through this. I fired the weapon today without the buffer retainer. 

I shot some 155, 125 and 110s. 

I had 2 of 10 of the 155s land on the table with me but the others were strongly ejected to the 2 o'clock quadrant. The ones that landed on my table were spinning like a helicopter rotor, I guess its just how they hit the deflector. 

The 125s and 110s come out to 3 o'clock very strong in a 12' arc. 

Oh, I re-tuned the SLR gas block, it is now out 9 of the available 15 clicks. 

[jtallen83]

Outside chance but new ejector and extractor springs solved a dribbling ejection issue for me, replaced unknown springs with some from Armalite. Cheap and if it doesn’t make a difference you have replacements on hand.