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mjsemtex

IRA-10D buffer damage.

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The only thing that argues against the buffer retaining pin hole being the issue is that the OP noted everything worked fine with a DPMS upper on the IR lower. 

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that's definitely something i can compare when i'm home later this afternoon.

wouldn't the 'stronger' spring cause even more damage to the buffer as it seems to slam into the retainer pin?

some of my concern also lies in the fact that the BCG isn't flush with the back of the upper as it is in all of my AR-15s... it would seem that instead of the buffer slamming home against the carrier group, the retainer is taking the brunt of the force. when i close the upper down onto the lower, there does seem to be a gap between the buffer and the rear of the BCG.

Just reading that part of his post , it seems the BCG is sticking out ,but its not contacting the buffer & pushing it away from the stop.

No matter what it is , its still a manufacturing defect, both upper & lower made by same manufacturer..

He never said how long the DPMS upper was on there , so it may have taken a while for the buffer to start showing signs of a beating.

I don't think he posted any photo's to see fitment of components , least ,I don't remember seeing any .

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I was able to track down the OP, and he confirmed that

with both a factory-assembled DPMS upper, and with a factory DPMS upper with the same barrel and barrel extension and BCG, the BCG would make contact with the buffer when the uppers were put together in the IR lower. 

When he used the same BCG, barrel and extension on the IR upper, there was no contact between the BCG and the bolt.

Assuming the two DPMS uppers were to DPMS spec, it seems the issue is with the IR upper. 

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I happen to have a Starrett Depth Gauge and a stripped Iron Ridge upper receiver. 

I can take a few measurements of the upper.  Anyone have any suggestions?  I thought the barrel thread would be a start. 

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I seem to remember that the buffer damage that was pictured by the OP was much more severe than the damage I saw on the buffer in the lapping tutorial. The pics that were on the AR 15.com post are so blurry that I can't see how bad that buffer is. As I recall there was also the question of why the back of the BC didn't contact, and push the buffer off the buffer retainer when you mated the upper and lower together. I don't see how smoothing/deburring the back of the BC is going to change that. Maybe I can ask this question, The BC should "head space" far enough back in the upper so that it does in fact depress the buffer spring slightly, thereby pushing the buffer off the retainer, right? That's not an unimportant dimension, is it? If so it comes back once again to something locating the BCG further forward in that upper than is normal. Either something wrong dimensionally with the upper, the BCG (unlikely) or the barrel extension, and I guess also the buffer retainer bore  could be mislocated. Although, I have not been involved with the AR's all that long and have not experienced all of those weird things that the long time AR guys I'm sure have, I have yet to see the kind of wear on any of my buffers from any of the BC's in my AR's. That includes, DPMS, Armalite and Young's BC's. If I was the owner of that IR receiver set, I'd find a way to compare my gun dimensionally to another DPMS type  .308 AR that I knew to be good,and determine once and for all what (if anything) was dimensionally different on my gun from the one I knew to work,  and if I found a noticeable dimensional difference that was causing the problem, I'd be on the phone with IR. As much as I don't think you should need to resort to things like that to remedy the problem, If all it took to solve it was one of those silicone bumpers I'd do it in order to have a working gun. Something else comes to mind, I recall reading that the carrier weight system required you to pull both the front and rear pins to  install it and be able to open and close your AR. I'm thinking that if the problem with this one is the BC being too far forward, You might be able to add one of the CWS to add some length to the BC, solve the buffer damage problem and maybe you'd still be able to open and close that particular gun in the conventional manner, without having to pull the pivot pin?

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My  AR 308 Uppers measure , from the barrel extention face to the outside edge of the upper receiver .Barrel attached .

DPMS                  -7.867"

SIDefence (billet)  -7.899"

Even with some error in my measurements , they are real close to each other .

Now with a bbl. attached to the IR upper , what would that show ? .

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Interesting.  Take a look at the threaded barrel port on these receivers. 

Check out the second image of the DPMS receiver in this link:

http://www.brownells.com/.aspx/pid=43844/Product/_308_AR_STRIPPED_UPPER_RECEIVER

Now the image of the Iron Ridge upper from their website:

http://www.ironridgeguns.com/ira-x-complete-lowers/

Now the image of the SI Defense Upper:

http://shop.si-defense.com/SI_Defense_308_7_62_Generation_III_Upper_Receiver_p/si%20308%20upr-dpms-gen3.htm

Iron Ridge has an unthreaded portion at the front, and puts the barrel pin slot in the unthreaded portion (as opposed to cutting it into the threaded portion like DPMS and SI).  In addition, the barrel threads on both the DPMS and SI uppers go the entire length of the barrel port extension on the receiver, where Iron Ridge has both a front and rear unthreaded portion.

A recent poster over at AR 15 noted that the BCG was about 1/8" from the buffer when the receiver halves were locked in.  The unthreaded part of the IR barrel port measures about .1685".  An eighth of an inch is .125", and 3/16 is .1875". Just wondering whether this is where the issue lies. 

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Man, this just keeps getting better .

The threaded or lack of ,portions of the uppers barrel's , would probably not mean a thing , as long as the barrel extensions flange seated to the same dimensions, as the others .

Now if the barrels extension was seated too far forward , that would put the BCG forward also & in turn would leave the BCG forward of the buffer .

That would bring up some easy fixes ,but how do you know all of the IR uppers are all out of spec's , this may by an isolated few receivers , that are being effected.

I would start by getting another manufacturers upper with known proper functioning characteristics & start taking measurements .

If all it is ,is the bbl. is too far forward , the face of the upper ,where the barrel extension flange seats , could be cut back , along with the indexing slot , but how would you know the cam slot & other dimension's would not be out of spec's by doing that.

Nice can of worms opened here.

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Man, this just keeps getting better ...

I would start by getting another manufacturers upper with known proper functioning characteristics & start taking measurements .

If all it is ,is the bbl. is too far forward , the face of the upper ,where the barrel extension flange seats , could be cut back , along with the indexing slot , but how would you know the cam slot & other dimension's would not be out of spec's by doing that.

Nice can of worms opened here.

I hope to have a DPMS upper in my hands by tomorrow, and may be able to get ahold of an SI upper to check in the next week or so.

Planning to measure the length of the threaded barrel flange on all 2, plus the distance from the top of the flange to the gas tube channel were it ends on the inside of the upper receiver.  Then take a look at the BCG slots on the inside of each receiver and perhaps measure those if they are not consistent. 

The Starrett inside depth micrometer is going to get a work out.....

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The threaded extension on the front of the upper receiver would have to be cut back to allow the barrel to seat further back.  Also, the notch for the barrel index pin would need to be deep enough to allow for barrel to come back.  Both those things would need to be fixed.  That would seat the barrel, with barrel extension, further back in the upper housing, and would make the BCG protrude further out in the back. 

You'd need to "see/precisely measure" how much gap you have between the back of the BCG and the face of the buffer, in order to determine how much material needs to disappear from the threaded extension on the front of the upper receiver.  The depth of the barrel index pin from the seating flange on the barrel will determine how deep the index slot need to be, in order to fully seat the barrel in the upper receiver.

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Threaded barrel extension on the receiver is .687".

.1685" to first thread from front.

Had a chance to do some quick measurements on a DPMS A3 upper receiver.

.6505 DPMS  Difference to IR - IR+ .0365

.0365 fals into the range of between 1/32 and 3/64, so that might explain some of the difference. 

The other thing I noticed is that with the DPMS, there is no distance from front of flange to first thread.  The DPMS is threaded all the way up.

There is a .089 distance from front of the DMPS upper receiver to the bottom thread on the flange.  I have not measured the Iron Ridge for this yet and will do it this weekend. 

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Done with the preliminary measurements on the barrel flange.  All measurements are in inches.

Iron Ridge

Threaded barrel extension flange on the receiver- .687".

Top of barrel flange to first thread - .1685"

Front of receiver to first bottom thread on barrel flange - .142 to .149

DPMS

Threaded barrel extension flange on receiver -.6505  DPMS  Difference to IR - IR+ .0365

Top of barrel flange to first thread – 0.00

Front of receiver to first bottom thread on barrel flange - .089

Differences Iron Ridge to DPMS

Threaded barrel extension flange on receiver - IR+ .0365 (.0365 falls into the range of between 1/32 and 3/64, so that might explain some of the difference. )

Top of barrel flange to first thread – IR  +.1685" (not sure how much this would effect barrel depth into the receiver, but that falls in to the range of 5/53" to 11/64"))

Front of receiver to first bottom thread on barrel flange – IR  + .053  to .06 (that falls in between 3/64" and 1/16")

Tools used were a Starrett depth gauge for depth measurements and a Starrett inside/outside electronic caliper.  I am not a machinist, but I re-verified each reading at least 5 times. 

The other thing I noticed is that there is a small gap between the DPMS upper receiver when mounted to the Iron Ridge Lower.  If I can locate my gap gauge, I'll see where that comes in. 

Any thoughts? 

I'll update as I think of and take additional readings and measurements. 

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Some other measurements

Length of upper receiver (excluding barrel flange) - both mearued the same to the 32nd inch using a Starrett steel

Top groove in upper receiver for BCG - both mearued the same to the 32nd inch using a Starrett steel

Thickness of front of upper receiver face (where the front pivot pin hole is located):

Iron Ridge - .554

DPMS - .594

Gas tube hole in upper receiver - measured from the top of the barel flange to the opening inside of the upper

Iron Ridge - 1.335

DPMS - 1.297

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Since the original poster no longer has his IR receiver, we'll never know how his upper's dimensions compared to yours, but for academic purposes, I'd say that it sounds as though, assuming that you were to use the same barrel, your IR upper should locate the BCG .036" further forward from the front shoulder of the IR upper compared to the DPMS upper, Now, maybe I misunderstand some of your measurements but, as I understand it your saying that the two uppers are the same OAL front to back right? The key thing you have to determine unless you've already done it and I didn't get your measurements correctly, is that you have to make sure that the front pivot pin bore (which actually locates the upper on the lower in relation to the buffer) on both uppers is located in the same place in relation to the front and/or back face of the upper receiver. If that is the same on both, I would think that your IR receiver set should not have the problem that the first poster's had..

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Done with the preliminary measurements on the barrel flange.  All measurements are in inches.

Iron Ridge

Threaded barrel extension flange on the receiver- .687".

Top of barrel flange to first thread - .1685"

Front of receiver to first bottom thread on barrel flange - .142 to .149

Do you have an Iron Ridge upper in-hand that you're making these measurements from?

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Have you tried this IR upper to see if it has the same problem as the org. poster's ?

There just may be some out there that are way out of spec's .

Jgun , good idea about the pivot pin placement .The out of spec uppers may have more than one thing ,out of spec. 

You say the DPMS has more of a gap between the upper & lower @ the back,  than the IR ,upper & lower mated ?

Great job measuring , that took some time .

I guess it all comes down to how it fits when assembled with a bbl..

Ya know ,one thing crossed my mind , how do we know that they didn't produce the uppers with a gap  between the BCG & Buffer, on purpose.

We knows its not right ,but maybe there designers had some reasoning for it .

Far fetched ,yes , but you never know .

They did say they are all that way .

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Has there been any more recent news or response from the company on this issue?

I ask since I'm planning a build and was considering IRA since I live in CO.

I think I'll email them and ask straight up what the deal is with their out of spec receivers.

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I think I'll email them and ask straight up what the deal is with their out of spec receivers.

Direct contact would be your best bet, but a phone call - talking to a human - would probably be the better option, before email.  It's hard to verbally talk to someone and skirt an issue, but it's really easy to "talk around something" in email. 

If I was spending that amount of money on an upper and lower, I'd want to know who I talked to, what time/date I talked to them, and what they said.  Not being paranoid here, but that's no small chunk of change.  Hell, if I was local, I'd drive there and talk to them face to face, prior to.  <dontknow>

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I've got the same "damage" to my buffer but using a DPMS upper on a POF lower. The lower receiver pictured is not a POF lower as I've move the buffer to another lower receiver. I'll be testing a new IR upper with a TM lower next with a new buffer to see if the same damage occurs. I'll also take a picture on my friend's DPMS upper on a TM lower to see if there's buffer damage.

img0845ay.jpg

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I've got the same "damage" to my buffer but using a DPMS upper on a POF lower.

Honestly, we (the membership here) have seen issues like this, and it's most often when you mix and match uppers and lowers.  Since there's no standard to go from (like the AR-15s following the Colt TDP), different companies can do whatever they want as far as design and execution.  Mix and match contributes greatly to the possibility that your stuff might have problems.  This original IRA issue here is different - a big problem, denied mostly by them, and parts from the same manufacturer. 

A Tubb Carrier Weight System will solve your buffer-damage problem.

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