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Post by Babaganoush on Dec 8, 2012 20:53:26 GMT -8
I've just gotten back from the range with my new 264 build, and am quite frustrated.
20" BHW Match Bull Barrel.
Bolt from Tac Ammo.
UR is DPMS
LR are DPMS or M&P
The rifle is experiencing a fail to feed problem. The round is shoved part way up the feed ramp, and the bolt rides over the case.
It occurs when chambering the first round about 30% of the time (using the bolt catch or sling-shotting the charge handle.) It doesn't seem to matter how many are in the mag when that happens.
It also occurs when firing the last round or two in the magazine. The first n-2 rounds will cycle, but the last round or two FTF with the same bolt ride over and round halfway up the feed ramps.
Only other symptom I can think of is a slightly dented case mouth on all fired brass.
I've tried the following:
Replaced both Gas Block and Gas tube.
Swapped Bolt Carrier.
Swapped magazines (tried both AR-Stoner 10's and ASC 17's).
Swapped Lower Receiver.
Swapped Buffer Assembly.
Different Loads. (All 123gr Amax, Hornady cases, CCI 450 primers, and charges of IMR-8208 from 26.6 gr to 28.4 gr)
The only change seen was when swapping the Rifle Length buffer assembly (Buffer, Tube and Spring) for a Carbine length assembly. The FTF on the last round or two almost goes away (3 of 4 succeeded), but it then doesn't lock open on last. No change to first round feeding issues.
Other than that, everything is fine. ;D
Any thoughts from those who know all, see all and (hopefully) tell all?
David
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Post by Master Yoda on Dec 8, 2012 22:10:38 GMT -8
please send the complete upper to us and I will look at it for you
Carl
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Post by Babaganoush on Dec 9, 2012 12:48:41 GMT -8
please send the complete upper to us and I will look at it for you Carl Thank you very much, Carl. I really appreciate the help. David |
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Post by Babaganoush on Dec 21, 2012 23:50:26 GMT -8
Carl,
Before I sent the upper in, I took a step back and had one more look at the "big picture". This weapon was a frankengun from the word go, and I thought I'd checked all the variables. The one thing I didn't check was the upper receiver, which I really hadn't considered a possibility.
I decided it to swap it out with another upper and was finally rewarded with the sound of rounds chambering with 100% success. No serious marks on either the cases or on the bullets. I haven't live fired, as yet, but this was very encouraging.
On close examination of the problem upper, I found a very slight inward bow on the ejector side of the mating surface. I then discovered a tell-tale shiny spot on all the magazines, approximately where the bowed section would meet the mags. While I never noticed any difficulty inserting the magazines, I can only conclude that the upper was preventing them from seating deeply enough to allow the bolt to reliably pick up the cartridges.
In any case, I'll be out shooting this fella over the weekend and will let you know if the FTF issue has been completely resolved.
David
p.s. Have a Blessed Christmas.
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Post by GLSHOOTER on Dec 22, 2012 13:23:12 GMT -8
Carl, Before I sent the upper in, I took a step back and had one more look at the "big picture". This weapon was a frankengun from the word go, and I thought I'd checked all the variables. The one thing I didn't check was the upper receiver, which I really hadn't considered a possibility. I decided it to swap it out with another upper and was finally rewarded with the sound of rounds chambering with 100% success. No serious marks on either the cases or on the bullets. I haven't live fired, as yet, but this was very encouraging. On close examination of the problem upper, I found a very slight inward bow on the ejector side of the mating surface. I then discovered a tell-tale shiny spot on all the magazines, approximately where the bowed section would meet the mags. While I never noticed any difficulty inserting the magazines, I can only conclude that the upper was preventing them from seating deeply enough to allow the bolt to reliably pick up the cartridges. In any case, I'll be out shooting this fella over the weekend and will let you know if the FTF issue has been completely resolved. David p.s. Have a Blessed Christmas. It sounds like when it was barreled up the clam shell, if that was used, was tightened excessively and collapsed the upper inward. Not common but know to happen. Greg |
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Post by Babaganoush on Dec 23, 2012 17:54:58 GMT -8
It sounds like when it was barreled up the clam shell, if that was used, was tightened excessively and collapsed the upper inward. Not common but know to happen. Greg Greg, It's entirely possible. The upper was new, and I did use a clamshell holder.  Either way, the little bugger is bent, and I will need to find a way to salvage the upper. In the current panic buying climate, I doubt another will be available for some time. You'd think someone thought the world was coming to an end, or something. ;D David |
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Post by GLSHOOTER on Dec 24, 2012 9:37:32 GMT -8
It sounds like when it was barreled up the clam shell, if that was used, was tightened excessively and collapsed the upper inward. Not common but know to happen. Greg Greg, It's entirely possible. The upper was new, and I did use a clamshell holder. Either way, the little bugger is bent, and I will need to find a way to salvage the upper. In the current panic buying climate, I doubt another will be available for some time. You'd think someone thought the world was coming to an end, or something. ;D David Lots of uppers out there. Here you go: www.rguns.net/gunparts/rifle-parts-AR-uppercomponents-UpperReceivers.shtmlMerry Christmas. Greg |
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Post by Babaganoush on Dec 24, 2012 13:17:02 GMT -8
Sweet - Thanks for the lead. Perhaps I assumed to much. New Upper on the way. Merry Christmas! David |
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Post by Babaganoush on Dec 27, 2012 14:13:27 GMT -8
;D Yay!
Just back from the range, and everything is functioning perfectly! Only had a minor issue at the beginning with a slightly misaligned gas block but once I took care of that, everything fed, cycled and ejected as it should.
A little case mouth denting is the last bit to resolve, but some velcro and/or an ejector spring mod should resolve that.
Groups very well with 28 grains of 8208 pushing the 123 grain Amax's.
Going out Saturday to work up a long range ballistics table.
Thanks for the help!
David
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Post by GLSHOOTER on Dec 27, 2012 15:37:03 GMT -8
;D Yay! Just back from the range, and everything is functioning perfectly! Only had a minor issue at the beginning with a slightly misaligned gas block but once I took care of that, everything fed, cycled and ejected as it should. A little case mouth denting is the last bit to resolve, but some velcro and/or an ejector spring mod should resolve that. Groups very well with 28 grains of 8208 pushing the 123 grain Amax's. Going out Saturday to work up a long range ballistics table. Thanks for the help! David Next time squeeze lemons and not the upper!! ;D Greg PS: Glad to here it runs now. |
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Post by Babaganoush on Dec 27, 2012 20:35:23 GMT -8
Next time squeeze lemons and not the upper!! ;D Greg PS: Glad to here it runs now. Yeah - that way I can at least enjoy the lemonade! I've ordered a better upper clamshell to replace the POS I used. It always seems to come down to the adage "Buy cheap, buy twice". No two ways about it, though - it has been an education on several aspects of this build. Now time to stretch its legs! |
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