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Grizzly
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Posted: 7/24/2011 2:07:34 PM
Anyone have any information on the interior dimensions for the upper receiver.

Just tried to assemble my new Iron Ridge upper to the lower - there is about a 1/8" gap the bolt carrier and the buffer when closed.
With a 5.56 platform, the BCG is supposed to set the buffer back a tad to relieve the pressure on the buffer pin.

Have the correct buffer, buffer spring, butt extention, barrel and barrel extension. Same problem with both DPMS and Young carriers.

I found this older thread:
http://www.ar15.com/forums/t_3_121/523096__ARCHIVED_THREAD____iron_ridge_arms_IRA_10___IRA_X_uppers___lowers_.html&page=2

And this one over at SH: http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2377596

I recall that that thread at SH got the OP banned.

It would not be a surprise if a few out of spec uppers got released.

I was a little trouobled to see some past recommendations on other boards on how to deal with the issue - glue something onto the buffer, etc. That is a patch, not a fix.

Looking at some of archived threads here, it appears there were 2 or more other members who had similar problems.

Anyone else have this issue, and if so, is there a solution absent going with another manufacturer?

I
98Z5V
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Posted: 7/25/2011 1:31:43 AM
The Tubb CWS will add 0.080" to the length of your bolt carrier, but that's not enough to bridge an 1/8" gap.
survivalshop
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Posted: 7/25/2011 11:07:19 AM
Another one !

I would send the complete rifle or the upper & lower back to the manufacturer & let them know , not to just put a band aid on the problem.

Could be upper & or lower out of spec..

They know by now they are out there. I have seen a post by IR., on another sight , that said to send it back to them . I would !

Putting the Tubbs system is a fix & will work ,but its still just a band aid.
Grizzly
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Posted: 7/29/2011 10:24:47 AM
Thanks for the replies.

I suppose the bigger question here is what should we reasonably expect from a manufacturer when they claim their products to be "DPMS" or "Armalite" style?

I saw the drill the others had to go through with Iron Ridge - from what I read, IR claimed the receivers were fine, this kind of thing was "normal", and the band aid on the buffer was the "fix".

Maybe I am expecting too much, but my thinking is that when someone offers a DPMS receiver, it should actually be made to those specs. Not a "you can use DPMS parts, but midificaitons will be required to get it right".
survivalshop
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Posted: 7/29/2011 1:18:25 PM
I measured my DPMS & my SI defence (billet )uppers from the barrel extension face to the outer face of the upper receiver ,where it would meet the lower receiver . As you can see there is not much difference & some of it could be me, measuring them .

SI defence –– 7.899 "

DPMS –––––– 7.867 "
jeffrey_wayne
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Posted: 7/31/2011 4:09:41 PM
seems like i have the same issue.... have you contact them yet?

http://www.ar15.com/forums/t_3_121/543781_what_happen_to_my_buffer___need_some_help___.html
hotdog250j
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Posted: 7/31/2011 11:11:16 PM
Originally Posted By survivalshop:
I measured my DPMS & my SI defence (billet )uppers from the barrel extension face to the outer face of the upper receiver ,where it would meet the lower receiver . As you can see there is not much difference & some of it could be me, measuring them .

SI defence –– 7.899 "

DPMS –––––– 7.867 "


.030" (30 thousanths) is a LOT.
its 3/4 of a millimeter.
asuming its not even more, because its hard to measure that far without positive stops.
i bet the carrier doesn't even push back the buffer that far.
the rear of the carrier should be flush with the upper.
the front of the buffer should protude from the lower.
the upper and lower should fit together without a crack.
therefore the carrier pushes the buffer back a slight amount when closed.
All I want is compliance with my wishes, after reasonable discussion.- Winston Churchill
madcratebuilder
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Posted: 8/1/2011 10:14:02 AM
Originally Posted By Grizzly:
Thanks for the replies.

I suppose the bigger question here is what should we reasonably expect from a manufacturer when they claim their products to be "DPMS" or "Armalite" style?

I saw the drill the others had to go through with Iron Ridge - from what I read, IR claimed the receivers were fine, this kind of thing was "normal", and the band aid on the buffer was the "fix".

Maybe I am expecting too much, but my thinking is that when someone offers a DPMS receiver, it should actually be made to those specs. Not a "you can use DPMS parts, but midificaitons will be required to get it right".



"DPMS" or "Armalite" style should not make any difference. If the buffer is contacting the buffer retainer when the bolt is locked, then there is a problem with the buffer retainer hole position, or the chamber is allowing the bcg to move to far forward.

I run the back of the bolt carriers over a flat stone to ensure they are free of any burrs. I have never had any wear issues with the buffer face, The anodizing well start to show wear after some time.

I'm surprised IR claimed the receivers were fine, this kind of thing was normal. It is not normal

Grizzly
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Posted: 8/1/2011 11:28:37 AM
Originally Posted By madcratebuilder:



"DPMS" or "Armalite" style should not make any difference. If the buffer is contacting the buffer retainer when the bolt is locked, then there is a problem with the buffer retainer hole position, or the chamber is allowing the bcg to move to far forward.



This appears to have been the issue with the first person to report a problem. The IR lower worked just fine with two separate DPMS uppers - contact between the NCG and buffer. Could be an issue with the barrel mount, the BCG groove in the top of the upper or something else. Whatever it is, I agree it is not normal. The buffer retaining pin is not going to take a constant pounding like that, especially from a heavier .308 buffer. At some point, it is going to shear off, and potentially knock the sheared pin into the FCG. Maybe no big deal on a range, but when hunting hours away from a shop missing the trophy of a lifetime or, in a LE situation, when all is riding on everything functioning as it should, it could be more than a small problem.

For a $500 upper, you shouldn't have to sweat that stuff.
Grizzly
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Posted: 8/6/2011 2:19:49 PM
This was posted over at .308 AR.com under the "Iron Ridge" forum:

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?


So, if the barrel is not seating far enough into the receiver, the BCG may not properly seat against the buffer?