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I have an SBR built on Midwest industries upper and lower with a 10.5 inch barrel. I use the weapon as my daily patrol rifle. Upon taking ownership of the gun it ran flawless. I qualified with it and practiced with it all without a hiccup. After approximately 750 rounds I started experiencing failure to feed and failure to eject. I stripped it down and cleaned it very well. This fixed the problem for approximately 60 rounds, then it returned. I have tried different ammo with no effect. I have noticed that it tends to rear its ugly head once the gun is warmed up a bit. It will run fine for the first mag or so then starts the failures. To be more specific about the failure, it will fire and eject but then fail to strip the next cartridge out of the magazine. (Yes I have tried different mags) a few things I have read says my buffer spring is too weak, some say it’s too strong. Some literature points to undergassing. Some points to overgassing.
PLEASE help. The guy who built it was of no help and has since shut his doors. I know the collective knowledge here has to have an answer or a solid suggestion.
Thanks
What is the BCG?
I'd check into extractor spring replacement, or try a different BCG of known quality.
What weight buffer? It should be marked on the front of the buffer H1, H2, etc. Measure your action spring (buffer spring) relaxed, out of the rifle. Should measure 10 1/16” to 11 1/4” in length (carbine).
Check for markings on the barrel, etc to try to let us know more specifically what kind of rifle we’re looking at.
Does it reliably lock back on empty mags? A lock back test will help us nail down the difference between too much spring or weight and not enough.
Make sure your carrier key isn’t loose.
I'd just add two things to 1168's post:
1) Short-stroking can also be caused by gas ring wear. You can test for gas ring wear by removing the bolt from the carrier and visually inspect the gas rings. Then insert the bolt all the way into the carrier without installing the cam pin. Turn the bolt carrier so the bolt is facing downward, if the bolt falls out then the rings need replacement. Given the history you related, worn gas rings wouldn't be my first suspicion, but the check is so easy you might as well cross it off the list.
2) I would guess that your rifle will run on either a carbine (generally unmarked, weight about 3.0 oz) or H (generally marked H or H1, about 3.8 oz) buffer. If it has an H buffer and your spring measures 10 to 11, I'd try a carbine buffer (and mistrust the rifle until I was SURE - .8 oz is not that much). If it has an H2, drop back to an H and check function.
3) If everything seems to check out with no problems, try the SBR using another BCG.
Mr. Goodtimes
11-25-17, 22:47
I would try a new buffer spring. If that doesn’t fix the issue, if you have a carbine buffer then I would try an H or H2. Maybe try new gas rings if nothing else works. 10.5’s tend to be pretty gassy.
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I would try a new buffer spring. If that doesn’t fix the issue, if you have a carbine buffer then I would try an H or H2. Maybe try new gas rings if nothing else works. 10.5’s tend to be pretty gassy.
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Gas port spec is key for sure
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I would try a new buffer spring. If that doesn’t fix the issue, if you have a carbine buffer then I would try an H or H2. Maybe try new gas rings if nothing else works. 10.5’s tend to be pretty gassy.
I started experiencing failure to feed and failure to eject.
I stripped it down and cleaned it very well. This fixed the problem for approximately 60 rounds
To be more specific about the failure, it will fire and eject but then fail to strip the next cartridge out of the magazine.
We seem to have reached opposing conclusions, these are my thoughts:
Without a good description of the fail to eject, it is hard to determine if the extractor is losing control of the case, or if the action isn't cycling far enough to allow the case to eject.
The action not completely cycling and failing to eject kind of meshes with not picking up the next round from the mag.
So that leads me to believe over buffered/sprung or undergassed as the simplest explanation.
What do you think?
First thing to do is a lockback check to see if it's short stroking.
I would read this first and then come back with some additional info.
https://www.m4carbine.net/showthread.php?193117-Basic-Troubleshooting-101
I started experiencing failure to feed and failure to eject.
I stripped it down and cleaned it very well. This fixed the problem for approximately 60 rounds
To be more specific about the failure, it will fire and eject but then fail to strip the next cartridge out of the magazine.
We seem to have reached opposing conclusions, these are my thoughts:
Without a good description of the fail to eject, it is hard to determine if the extractor is losing control of the case, or if the action isn't cycling far enough to allow the case to eject.
The action not completely cycling and failing to eject kind of meshes with not picking up the next round from the mag.
So that leads me to believe over buffered/sprung or undergassed as the simplest explanation.
What do you think?
This is my suspicion. But more info required, for sure. That lockback test may be the key.
JD Williams
11-26-17, 12:19
I would read this first and then come back with some additional info.
https://www.m4carbine.net/showthread.php?193117-Basic-Troubleshooting-101
When I clicked the link there were only two posts that did not have a complete list. Looks like it was cut off at 4 and prior listings.
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Everything in my original post is showing up for me.
When I clicked the link there were only two posts that did not have a complete list. Looks like it was cut off at 4 and prior listings.
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JD Williams
11-26-17, 14:06
Everything in my original post is showing up for me.
Must be my equipment. Thanks.
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1. The buffer is unmarked
2. The bolt will lock open after last round
3. The gas key is mounted solid
4. Buffer spring is correct length
So......would I be better off buying a lower weight spring or buffer? Or a heavier weight spring??
For $4 I would replace the ejector spring with the copper colored Colt version.
Colt copper colored spring, no black O-ring.
At least that would eliminate that potential aspect that several of us have experienced.
1. The buffer is unmarked
That's the first, and most obvious problem. It's likely a carbine buffer, which is a good solution for NO AR15 that I'm aware of. H2 is what should be in any carbine system that's close to being correctly gassed.
A carbine buffer will give you WAY TOO MUCH bolt speed and cause lots of problems.
What kind of ammo were you shooting? Who is the barrel manufacturer?
So far it sounds like you need a heavier buffer like an h2.
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Windham 10.5 inch barrel. I was shooting a mix of ammo. UMC 55 grain fmj, hornady 55g, xm193, some handloads, all with the same outcome. It typically only happens when the gun gets hot or I fire at a faster rate.
Why would it begin after the fir initial 400-500 rounds? Up until then it ran like a top.
Probably the bolt carrier group is broken in, rings, etc. And now that excessive bolt speed is causing the gun to run too fast. I'm sure Windam likely has a port on the larger end. An H2 should make that thing run a TON better.
So I had the same issue with a very well known manufacturer and the issues turned out to be with the BCG, again for a tier one manufacturer. If you have an extra BCG I would throw it in and see if it runs before changing anything as you mentioned it used to run perfect.
Already tried another BCG. Runs the same
Midwest Industries
12-11-17, 13:53
Do you live local to us by chance?
Thank, Peter
Windham 10.5 inch barrel. I was shooting a mix of ammo. UMC 55 grain fmj, hornady 55g, xm193, some handloads, all with the same outcome. It typically only happens when the gun gets hot or I fire at a faster rate.
Why would it begin after the fir initial 400-500 rounds? Up until then it ran like a top.Typically a rifle's cyclic rate will increase slightly during the first few hundred rounds and also as the rifle gets hot. And mags get dirty/broken in as well which can slow down how fast the next round is presented. I bet your rifle was on the ragged edge to start with, because it's a 10.5 Windham(not the best) barrel, with carbine buffer. It isn't short stroking because it is locking back. The bolt is out running the magazine.
I'd get an h2 or even h3 from bcm, and order a bcm carbine spring while you are at it just to be sure.
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Typically a rifle's cyclic rate will increase slightly during the first few hundred rounds and also as the rifle gets hot. And mags get dirty/broken in as well which can slow down how fast the next round is presented. I bet your rifle was on the ragged edge to start with, because it's a 10.5 Windham(not the best) barrel, with carbine buffer. It isn't short stroking because it is locking back. The bolt is out running the magazine.
I'd get an h2 or even h3 from bcm, and order a bcm carbine spring while you are at it just to be sure.
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That's the most likely scenario.
Barrel with giant gas port and cheap CAR buffer = super high cyclic rate and intermittent reliability.
Locks Back + Failure to Eject + Failure to Feed = Extractor Problem.
Install an M4 extractor spring from Colt or Sprinco. Once the extraction issue is solved, you can address any over gassing issues, if they exist.
Locks Back + Failure to Eject + Failure to Feed = Extractor Problem.
Install an M4 extractor spring from Colt or Sprinco. Once the extraction issue is solved, you can address any over gassing issues, if they exist.I agree with this too, except I would fix both issues at the same time(h3 buffer, bcm action spring, colt extractor and colt gold extractor spring)
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Locks Back + Failure to Eject + Failure to Feed = Extractor Problem.
Install an M4 extractor spring from Colt or Sprinco. Once the extraction issue is solved, you can address any over gassing issues, if they exist.
I'm not a big fan of masking overgassing with a beefy extractor. I agree with installing a BCM extractor kit... that's never a bad idea. But no gun will run good with that useless car buffer. Especially a Windom (probably .080" ported) barrel.
In the dark ages, people put those o-rings in their guns. I guess none of us really knew better at the time. But now we know better. An SBR will never run good with a CAR buffer.
I'm not a big fan of masking overgassing with a beefy extractor. I agree with installing a BCM extractor kit... that's never a bad idea. But no gun will run good with that useless car buffer. Especially a Windom (probably .080" ported) barrel.
In the dark ages, people put those o-rings in their guns. I guess none of us really knew better at the time. But now we know better. An SBR will never run good with a CAR buffer.
Mark, I think your assessment that the barrel in question is likely over gassed is dead on. But fixing the extraction issue won't mask that. I can tell you from experience that fixing the over gassing first, will mask the extraction issue. The extractor of an over gassed AR will not lose control of the case rim unless the extractor is out of spec, or the spring is weak. A good extractor & spring will tear the case rim before letting it go.
Whether or not a short AR will run with a carbine weight buffer depends on gas port diameter. I haven't tried it, but I betcha with a small enough gas port, a shorty will run fine with a carbine buffer. I've tuned a suppressed 11.5 inch AR to run reliably and with soft recoil with an H buffer. I imagine I can do the same with a carbine buffer. However, I feel a carbine buffer is too light. Tuning an AR to a carbine buffer will give a narrower span of operation. I certainly wouldn't tune a full auto AR to a carbine buffer.
I have never used a BCM extractor spring. But I have seen posts where it turned out the BCM extractor spring weakened, causing malfunctions like the one we're discussing here. Those malfunctions were occurring with carriers with about 1000 rounds on them. Some were new carriers.
The O ring was a Crane fix because the M4 originally used M16 extractor springs which weren't up to the job. Colt redesigned the M4 extractor spring to eliminate the problem but the .gov was slow in adopting it it because they didn't want to introduce a new part number into the system. The Colt spring is designed to be used WITHOUT the O ring.
Every time I needed to trouble shoot an AR, it's always been a waste of time If I didn't eliminate any issues the BCG might have first thing.
Could the OP clarify the original post please, the beginning part mentioned failure to eject, but the last part said the case was ejected. I didn't see failure to extract anywhere.
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Well to start, a carbine buffer is way too light for a 10.5" barrel.
1. The buffer is unmarked
2. The bolt will lock open after last round
3. The gas key is mounted solid
4. Buffer spring is correct length
So......would I be better off buying a lower weight spring or buffer? Or a heavier weight spring??
Could the OP clarify the original post please, the beginning part mentioned failure to eject, but the last part said the case was ejected. I didn't see failure to extract anywhere.
In his first post, Tnemt stated his SBR was having a failure to eject and a failure to feed. When an AR has a failure to eject with a failure to feed and locks back on the last round (Post #14), the usual culprit is the extractor. The extractor loses control of the case before it can be ejected. The unejected case blocks the feeding of the next round.
If it was a weak ejector, the empty usually dribbles out or causes a stovepipe.
In his first post, Tnemt stated his SBR was having a failure to eject and a failure to feed. When an AR has a failure to eject with a failure to feed and locks back on the last round (Post #14), the usual culprit is the extractor. The extractor loses control of the case before it can be ejected. The unejected case blocks the feeding of the next round.
If it was a weak ejector, the empty usually dribbles out or causes a stovepipe.In his first post he also says "To be more specific about the failure, it will fire and eject but then fail to strip the next cartridge out of the magazine. "
I'm not disagreeing with what you are saying can happen, however it may or may not apply in the OP's situation. The original post leaves some details up to the imagination. But one thing is clear, a car buffer has no place in a Windham 10.5 barrel gun.
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So for an update on my ongoing battle with my testy little rifle, I have replaced the standard buffer with a heavy weight h2 buffer. The rifle still does the same thing as before. Not sure what the deal is. Do I need a heavier spring? Do I need to order a light weight buffer/spring? I have a new big on its way for another rifle. I’ll drop it in and see how it goes.
When you conducted your lockback test, did you load one round in the magazine and then shoot it?
So for an update on my ongoing battle with my testy little rifle, I have replaced the standard buffer with a heavy weight h2 buffer. The rifle still does the same thing as before. Not sure what the deal is. Do I need a heavier spring? Do I need to order a light weight buffer/spring? I have a new big on its way for another rifle. I’ll drop it in and see how it goes.
"To be more specific about the failure, it will fire and eject but then fail to strip the next cartridge out of the magazine."
Is the bolt overriding the next cartridge or partially stripping it?
What magazines? Have you tried other mags?
"It typically only happens when the gun gets hot or I fire at a faster rate."
Broken gas key screw?
Have you done anything suggested previously in this thread to ensure extractor and ejector are up to snuff?
I know it's not the vogue thing to do these days, but I'm going to ask which direction it's throwing spent brass when it does eject?
Clean it so it will run, and then run it and watch over time where the brass is going until it starts failing.
Even a minor indicator of bolt speed would be really helpful.
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