 BigJimboGee 
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Joined: Nov 2011  NM, USA
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Posted: 8/3/2012 2:31:32 PM
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RedFalconBill
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Joined: Mar 2005 PA, USA
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Posted: 8/3/2012 2:35:04 PM
Originally Posted By BigJimboGee: Just wanted to see if anyone had any suggestions on some issues that a friend of mine is having. He has a carbine length that keeps failing to eject with xm855. Today at the range we tried swapping my lower with his upper and experience no failures. We figure it must be his lower so we put my upper on his lower and also experienced no malfunctions (both of our AR's are carbine length with the same buffer setup). Then we put his rifle back together and started having malfunctions again. We then swapped out his bolt carrier group with a brand new RRA BCG and still had the malfunctions. He then started shooting Tulammo .223 and the malfunctions stopped. Nothing that was happening made any sense to me, so hoping it makes sense to someone else. I thought maybe a bad lot of ammo, but like I said we had no malfunctions putting it through my upper. Thanks guys. What type of FTEx are you having? Does the RRA bolt have a 5-coil extractor spring, or if not does it have an O-ring/D-fender? |
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Posted: 8/3/2012 2:46:41 PM
The failure is a stovepipe, then it feeds the next round into the stovepipe. I don't believe he has a O-ring on the extractor unless they come that way from the factory. The new bolt was also a factory RRA bolt carrier group.
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Posted: 8/3/2012 2:48:46 PM
some more info, the malfunctions started after he replaced his buffer tube and stock. But like I said before my upper ran with 0 malfunctions on his lower.
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Patriot556
Tier 1...Tier 2 whatever it takes.
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Joined: Jan 2012 MI, USA
Posts: 115 Feedback: 0% (0) Link To This Post |
Posted: 8/3/2012 3:53:26 PM
Originally Posted By BigJimboGee:
Just wanted to see if anyone had any suggestions on some issues that a friend of mine is having. He has a carbine length that keeps failing to eject with xm855. Today at the range we tried swapping my lower with his upper and experience no failures. We figure it must be his lower so we put my upper on his lower and also experienced no malfunctions (both of our AR's are carbine length with the same buffer setup). Then we put his rifle back together and started having malfunctions again. We then swapped out his bolt carrier group with a brand new RRA BCG and still had the malfunctions. He then started shooting Tulammo .223 and the malfunctions stopped. Nothing that was happening made any sense to me, so hoping it makes sense to someone else. I thought maybe a bad lot of ammo, but like I said we had no malfunctions putting it through my upper. Thanks guys. Things to isolate: 1.) possible the chamber is out of spec or dirty (make sure to clean the chamber) 2.) possible the ammo is out of spec, try a different lot number of the same brand, or a different brand of m855 ammo 3.) this last item is a remote possibility. If the rifle is new with relatively few rounds down the pipe, sometimes a particular rifle (no brand is immune and occurs from time to time) will require a break in period of several hundred rounds to loosen up. Get back to us with a update. |
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Posted: 8/3/2012 4:16:45 PM
[Last Edit: 8/3/2012 4:17:01 PM by SGHinds]
Originally Posted By BigJimboGee:
some more info, the malfunctions started after he replaced his buffer tube and stock. But like I said before my upper ran with 0 malfunctions on his lower. Put the old stock and tube on and see if the malfunctions stop. If so, there lies the issue. |
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WI57
Breath, Relax, Aim, Squeeze...
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Joined: Dec 2006 WI, USA
Posts: 7491 Feedback: 100% (15) Link To This Post |
Posted: 8/3/2012 4:43:41 PM
Originally Posted By BigJimboGee:
Just wanted to see if anyone had any suggestions on some issues that a friend of mine is having. He has a carbine length that keeps failing to eject with xm855. Today at the range we tried swapping my lower with his upper and experience no failures. We figure it must be his lower so we put my upper on his lower and also experienced no malfunctions (both of our AR's are carbine length with the same buffer setup). Then we put his rifle back together and started having malfunctions again. We then swapped out his bolt carrier group with a brand new RRA BCG and still had the malfunctions. He then started shooting Tulammo .223 and the malfunctions stopped. Nothing that was happening made any sense to me, so hoping it makes sense to someone else. I thought maybe a bad lot of ammo, but like I said we had no malfunctions putting it through my upper. Thanks guys. So it's his lower that is having the problems since the upper ran fine on your lower? |
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ricochet7
SI VIS PACEM PARA BELLUM
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Joined: Oct 2009 TX, USA
Posts: 1304 Feedback: 100% (117) Link To This Post |
Posted: 8/3/2012 4:56:45 PM
[Last Edit: 8/3/2012 5:14:50 PM by ricochet7]
Originally Posted By WI57:
Originally Posted By BigJimboGee:
Just wanted to see if anyone had any suggestions on some issues that a friend of mine is having. He has a carbine length that keeps failing to eject with xm855. Today at the range we tried swapping my lower with his upper and experience no failures. We figure it must be his lower so we put my upper on his lower and also experienced no malfunctions (both of our AR's are carbine length with the same buffer setup). Then we put his rifle back together and started having malfunctions again. We then swapped out his bolt carrier group with a brand new RRA BCG and still had the malfunctions. He then started shooting Tulammo .223 and the malfunctions stopped. Nothing that was happening made any sense to me, so hoping it makes sense to someone else. I thought maybe a bad lot of ammo, but like I said we had no malfunctions putting it through my upper. Thanks guys. So it's his lower that is having the problems since the upper ran fine on your lower? I see what you are saying, but the "it ran fine with Tula ammo" kinda sounds like a possible combination of problems. Could his upper be slightly overgassed with too light of a buffer? RRA uses a lighter BCG, and overgassed would still cause a too fast BCG (unless your other lower has a heavier buffer, or stiffer buffer spring<even tho you said alike>). I'm just guessing, but the Tula ammo statement made it sound like gassing/buffer problems. Just a guess 
On carbine gas length, if overgassed, the bolt starts pulling back maybe before swelling of the case in the chamber has lessened and the extractor pulls over the rim. Does the rim show any sign of ripping? Maybe adding a heavier buffer, the black o-ring (extractor upgrade), and maybe a new buffer spring? I'm still thinking slightly overgassed as the root of this, could be wrong (not the first time)... My .02 Re-edit- like buffers can weigh different (have seen this) and spring tensions can vary (as can inner diameter of the receiver extensions). I'd prolly try an H2 or H3 buffer and go again, for starters- is a cheap way to slow down bolt speed, and upgrade the extractor. |
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Posted: 8/3/2012 8:57:30 PM
Originally Posted By BigJimboGee:
some more info, the malfunctions started after he replaced his buffer tube and stock. But like I said before my upper ran with 0 malfunctions on his lower. The whole thing is a balance between several elements. Your friend has a rig and however it's "gassed", it was working with setup #1. Enter setup #2 with different action spring and different buffer, then everything stops. Seems to me, therein lies the culprit. |
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Patriot556
Tier 1...Tier 2 whatever it takes.
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Joined: Jan 2012 MI, USA
Posts: 118 Feedback: 0% (0) Link To This Post |
Posted: 8/3/2012 9:51:40 PM
Before you fiddle fart around spending money on springs and buffers. Highly recommend to at least exhaust the suggestions I proposed in the earlier post. The only thing you'll be out is a little time, some cleaner, and ammo.
Once you are certain those variables are exhausted, then begin breaking down the components of the rifle. Everyone seems to want to run about and replace parts. |
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Posted: 8/4/2012 3:24:27 AM
Originally Posted By ricochet7:
Originally Posted By WI57:
Originally Posted By BigJimboGee:
Just wanted to see if anyone had any suggestions on some issues that a friend of mine is having. He has a carbine length that keeps failing to eject with xm855. Today at the range we tried swapping my lower with his upper and experience no failures. We figure it must be his lower so we put my upper on his lower and also experienced no malfunctions (both of our AR's are carbine length with the same buffer setup). Then we put his rifle back together and started having malfunctions again. We then swapped out his bolt carrier group with a brand new RRA BCG and still had the malfunctions. He then started shooting Tulammo .223 and the malfunctions stopped. Nothing that was happening made any sense to me, so hoping it makes sense to someone else. I thought maybe a bad lot of ammo, but like I said we had no malfunctions putting it through my upper. Thanks guys. So it's his lower that is having the problems since the upper ran fine on your lower? I see what you are saying, but the "it ran fine with Tula ammo" kinda sounds like a possible combination of problems. Could his upper be slightly overgassed with too light of a buffer? RRA uses a lighter BCG, and overgassed would still cause a too fast BCG (unless your other lower has a heavier buffer, or stiffer buffer spring<even tho you said alike>). I'm just guessing, but the Tula ammo statement made it sound like gassing/buffer problems. Just a guess
On carbine gas length, if overgassed, the bolt starts pulling back maybe before swelling of the case in the chamber has lessened and the extractor pulls over the rim. Does the rim show any sign of ripping? Maybe adding a heavier buffer, the black o-ring (extractor upgrade), and maybe a new buffer spring? I'm still thinking slightly overgassed as the root of this, could be wrong (not the first time)... My .02 Re-edit- like buffers can weigh different (have seen this) and spring tensions can vary (as can inner diameter of the receiver extensions). I'd prolly try an H2 or H3 buffer and go again, for starters- is a cheap way to slow down bolt speed, and upgrade the extractor. ^^^This^^^.......over gassed systems cause ejection to occur late in the cycle, the round is trying to eject when the bolt is too far back. The bolt can cycle too quickly and travel back faster than the ejector can push the roud out. |
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Posted: 8/4/2012 3:38:23 PM
Over gassed is likely the problem, the gas port is huge on my my RRA (like .100" vs .065" on my Colt, over 2x the cross-sectional area), maybe a heavier buffer like H or H2 and regular BCG (or just H2 with no BCG?) when using the ammo with more ass?
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