View Full Version : Need assistance with AR malfunction.
Need assistance with AR malfunction.
Following the request for assistance format here:
https://www.m4carbine.net/showthread.php?t=85863
1&2. Colt Sporter 2 slabside, originally a 20” A2 rifle. Converted to carbine (i.e. standard hanguards, etc.) with all confirmed Colt parts, including:
a. Latest copper colored extractor spring w/ black insert from www.specializedarmament.com.
b. Colt 16” pencil barrel 1/9 twist (BTW, Are these rare as I usually see 1/7 or 1/12?).
c. Original Colt CAR/SP1 carbine buffer, buffer spring, buffer tube.
d. Original Colt FCG and Bolt Carrier Assembly (Half circle).
3. Ammo:
a. ~100rds - Factory fresh S&B 55gr FMJ in yellow & green box. This ammo functions in my FS2000 which seems to prefer stronger ammo. I have also shot about 600 rds from the same lot without problems. In fact, I prefer this ammo to PMC Bronze as the PMC won't function reliably in the FS2000 without changing the gas block to adverse.
b. ~60rds - Federal XM Greentip in stripper clips in cardboard sleeves. Also functioned fine in FS2000 fired same day.
4. This is the first time shooting since assembly. The sequence was as follows:
~60rds S&B in two different Colt 20rd mags,
then ~60rds Federal XM Greentip in two different USGI 30rd mags,
then ~40 S&B in the same two earlier Colt 20rd mags.
The carbine started malfunctioning during the last 30rds with both Colt 20rders, otherwise ran fine the whole day.
Malfunction description: An empty case fails to eject and another live round tries to feed. I didn’t have any cameras to take a pic. But this happened about 12 to 15 times and each time the malfunction visually appeared exactly the same. Which is to say, while looking through the ejection port, it looks like a double feed, except one round is fired and the other is live lying approx. parallel to each other.
The live round has a couple to a few very, very tiny dents as a result. During one malfunction sequence, I had to “yank” out the empty by hand, which was wedged into the gas tube void in the upper. Otherwise all the malfunction sequences were cleared by removing the mag and pulling the charging handle back, thus dropping the empty case and the live round through the magwell. Extractor does not appear to be chipped or otherwise damaged.
The ENTIRE carbine was cleaned spotless and the bolt group was VERY well lubed. As a matter of fact, I kept squirting more oil on it as a quick fix, but to no avail.
The range was closing so no time to diagnose further.
5. No mods to gas port.
I’m thinking the ejector/ejector spring but I wanted some of your opinions before I make anything worse.
Rockhopper
06-06-13, 21:29
undergassed?
saddlerocker
06-06-13, 21:43
Probably need a heavier buffer and maybe an O-ring around the extractor spring.
That bolt may not have the heavier duty extractor spring
Plus a 16" carbine usually runs best with an H or H2 buffer.
I would say your setup needs some weight added to slow things down
The extractor spring is the brand new, latest version (copper colored spring with black insert that came in a Colt baggie).
Heavier buffer?
I thought my problems is maybe the bolt carrier is not going back far enough to eject the empty. Do you think it is indicative of it going too fast and needs to slow down?
Also I will add to my original post: The bolt group was VERY well lubed. As a matter of fact, I kept squirting more oil on it as a quick fix, but to no avail.
I still don't understand why it functioned well for the first 120 or so rounds before acting up.
saddlerocker
06-06-13, 23:06
There could be a gas leak somewhere.
The carrier key is not loose is it?
Check the gas block/ gas tube/ gas rings
It could be short stroking, but Im just thinking the 16" carbine with a semi-auto carrier and carbine buffer is a pretty light setup.
Generally 16" Carbines run well with H2 buffers and M16 carriers
So I would think its an extractor issue or needs a heavier buffer or there is some kind of gas leak somewhere
There could be a gas leak somewhere.
The carrier key is not loose is it?
Check the gas block/ gas tube/ gas rings
I don't have the carbine with me at the moment, but I will check these suggestions.
It could be short stroking, but I'm just thinking the 16" carbine with a semi-auto carrier and carbine buffer is a pretty light setup.
Generally 16" Carbines run well with H2 buffers and M16 carriers
Could you clarify "pretty light setup?" Is this a good or a bad thing.
I am using basically the same internals as the original Colt SP1 carbine and I thought they ran OK. The only difference is the A2 upper....more or less a 6520, which I understand they also originally came with carbine buffers.
Another poster above also thought my setup is undergassed, which has me confused. So wouldn't a heavier buffer cause an undergassed system to run even more to the opposite of what I need?
Also, I thought the general consensus on M4carbine were that O-rings were unnecessary or were bandaids indicating a bigger problem.
Thanks for helping me diagnose this.
The issue according to your post is failure to extract which then results in the failure to feed. You are not having a double feed. The first thing I would do is use an H buffer. You to not need an O-ring. They are band aid.
Thanks for providing troubleshooting information per the requested format. That speeds things up.
Your setup should run. Nothing is obviously wrong or screwed to begin with. That's good.
It must be something more subtle.
Like brass shavings under the extractor shelf, or a stuck ejector.
Take the bolt down, remove the extractor and check the ejector.
The S&B ammo could be suspect, with either small rims or soft brass.
Measure some rims and try to inspect some ejected brass. Look for ripped or chipped rims.
Just to verify acceptable gassing, what direction were the ejected cases landing?
Also, next time out, swap BCGs if you can't find anything suspect on this one.
Thanks for providing troubleshooting information per the requested format. That speeds things up.
Your setup should run. Nothing is obviously wrong or screwed to begin with. That's good.
It must be something more subtle.
Like brass shavings under the extractor shelf, or a stuck ejector.
I fieldstripped the BCG and inspected the extractor and didn't see anything out of the ordinary, but will check again.
Take the bolt down, remove the extractor and check the ejector.
I will detail strip the bolt and check closely.
The S&B ammo could be suspect, with either small rims or soft brass.
Measure some rims and try to inspect some ejected brass. Look for ripped or chipped rims.
I left the fired brass at the range. I know, even in this day and age where everyone collects their brass, but I was so disgusted and the range was closing.
Just to verify acceptable gassing, what direction were the ejected cases landing?
A guy shooting to my right said he thought the empties ejected weakly, but he was shooting a trio of AK's (and clearly stated my situation is why he does so) so I don't know what his expertise on AR's is.
Also, next time out, swap BCGs if you can't find anything suspect on this one.
I have other Colt AR's (unfortunately I only brought this one AR today) and will try the BCG swap. I will also try an H-buffer upgrade as well. I have a pair of H2 buffers that I had for my still awaited Shrikes (But that's another story). Is it recommended to install the H2's (in lieu of H1's) to see what happens? Should I replace all my buffers in all my carbines as a precautionary measure? H or H2 or depends?
I'm not questioning the experts on this boards. I just have an inquiring mind. I'm just confused after all the years Colt made essentially reliable SP1/6420/6520 carbines with CAR buffers.
I appreciate everyone's help.
The old school carbines were not as reliable as a rifle. Heavy buffers and extra extractor tension made them.
I would use an H or H2 buffer. Inspect or replace the extractor. Check the ejector for free movement. If a little brass shaving gets down in there with the ejector it can randomly stop ejecting.
There is a vocal anti O-ring group on M4C, but it is simply a different way to get the needed extractor tension increase for carbines. You have the extra power "carbine" extractor spring so you should not use an O-ring. I choose to run standard rifle extractor springs with O-ring.
First, if it's a Failure To Extract, the spent case will stay in the chamber. Form your description that the spent case and the next round lay parallel to each other inside the action, it sounds as if the spent case is being extracted but not ejected. If this is the case, you are experiencing short stroking.
As the rifle ran fine at first, look to see what changed. Did you change ammo? If not, then it's likely the rifle has developed a gas leak someplace. Check the gas block- has it shifted either fore & aft or rotated to one side? Does the gas block have a good seal around the gas port? Is the gas block tight?
Check the bolt. Does it pass the gas ring check? To perform a quick gas ring check, extend the bolt in the carrier and set it on a table with the bolt face on the surface. If it closes from the weight of the carrier, the rings are suspect.
Is the gas key loose? If the gas key bolts are not torqued correctly, gas will escape between the key and carrier.
Also, a rifle may run fine with full power ammo, but leak just enough that using weaker ammo will result in short stroking. Or, it may be your rifle simply does not like weaker ammo
The issue according to your post is failure to extract which then results in the failure to feed. You are not having a double feed. The first thing I would do is use an H buffer. You to not need an O-ring. They are band aid.
IG, is this a failure to extract or a failure to eject? The empty case seems to be getting extracted but not being ejected based on his description.
From his post- However, I was having a hard time following his post so maybe I goofed.
Malfunction description: An empty case fails to extract (Extractor does not appear to be chipped or otherwise damaged.) and another live round tries to feed.
IG, is this a failure to extract or a failure to eject? The empty case seems to be getting extracted but not being ejected based on his description.
From his post- However, I was having a hard time following his post so maybe I goofed.
Malfunction description: An empty case fails to extract (Extractor does not appear to be chipped or otherwise damaged.) and another live round tries to feed.
I was reading the later description of an empty case and live round both loose in the action and locking up the gun, thinking maybe it's an ejector issue. Obviously it could be a number of things, but I was thinking ejector, extractor or possibly ammo?
From his post- However, I was having a hard time following his post so maybe I goofed.
Malfunction description: An empty case fails to extract (Extractor does not appear to be chipped or otherwise damaged.) and another live round tries to feed.
You are correct. I meant to say "An empty case fails to eject and another live round tries to feed."
Sorry for the confusion. I will edit that in the original post.
I should be able to get access to the carbine tonight or early tomorrow.
If that is the case then you need to replace the ejector spring. I would also check the ejector closely as well.
You are correct. I meant to say "An empty case fails to eject and another live round tries to feed."
Sorry for the confusion. I will edit that in the original post.
I should be able to get access to the carbine tonight or early tomorrow.
I finally inspected the carbine closely.
- FSB - Standard factory Colt FSB is solid as a rock with both taper pins GTG.
- Gas Key - BCG’s gas key factory Colt firmly staked well, solid as a rock with no gaps or movement.
- Extractor - is not chipped or damaged in any way and has strong spring tension.
- Ejector - has free movement and the spring tension is extremely strong. (I didn’t knock this pin out as I don’t have my small punch with me.)
- Gas Rings** -
MistWolf’s post: “Check the bolt. Does it pass the gas ring check? To perform a quick gas ring check, extend the bolt in the carrier and set it on a table with the bolt face on the surface. If it closes from the weight of the carrier, the rings are suspect.”
Well, it didn’t pass MistWolf’s test. I extended the bolt in the carrier and set it on a table and it closed from the weight of the carrier. I repeated this numerous times with the same result every time.
I opened up another Colt carbine I have and conducted the same test, and the carrier didn’t collapse down from its own weight at all through numerous tries.
I inspected the gas rings. The gaps were rotated evenly. Two of the three gas rings appear to have normal gaps. The third ring had a gap that was around five times normal. I will be replacing all three rings.
MistWolf’s test was a GREAT tip. I never heard of doing this. Is this rudimentary test common knowledge?
After the replacement of the gas rings, I‘m going to try to get some range time on Monday. I will bring an extra BCG with me this time, along with H and H2 buffers. I’m going to start with the CAR buffer first though to see if I can replicate my earlier malfunctions.
To those who said undergassed were spot on. Thanks to all who replied.
Out of curiosity and knowledge seeking, if undergassed I assume the BCG is not going far back enough for proper functioning. This might explain why the empty case didn’t eject. But apparently the BCG went back far enough to pick up a fresh round (which is much longer than an empty case) from the mag to try to feed. Can someone explain the dynamics of this, which I assume the term is “short stroking?”
Also, can anyone give additional guidance on how to change out the gas rings as they look real delicate.
replacement thread
https://www.m4carbine.net/showthread.php?t=48149
I finally inspected the carbine closely.
- FSB - Standard factory Colt FSB is solid as a rock with both taper pins GTG.
- Gas Key - BCG’s gas key factory Colt firmly staked well, solid as a rock with no gaps or movement.
- Extractor - is not chipped or damaged in any way and has strong spring tension.
- Ejector - has free movement and the spring tension is extremely strong. (I didn’t knock this pin out as I don’t have my small punch with me.)
- Gas Rings** -
MistWolf’s post: “Check the bolt. Does it pass the gas ring check? To perform a quick gas ring check, extend the bolt in the carrier and set it on a table with the bolt face on the surface. If it closes from the weight of the carrier, the rings are suspect.”
Well, it didn’t pass MistWolf’s test. I extended the bolt in the carrier and set it on a table and it closed from the weight of the carrier. I repeated this numerous times with the same result every time.
I opened up another Colt carbine I have and conducted the same test, and the carrier didn’t collapse down from its own weight at all through numerous tries.
I inspected the gas rings. The gaps were rotated evenly. Two of the three gas rings appear to have normal gaps. The third ring had a gap that was around five times normal. I will be replacing all three rings.
MistWolf’s test was a GREAT tip. I never heard of doing this. Is this rudimentary test common knowledge?
After the replacement of the gas rings, I‘m going to try to get some range time on Monday. I will bring an extra BCG with me this time, along with H and H2 buffers. I’m going to start with the CAR buffer first though to see if I can replicate my earlier malfunctions.
To those who said undergassed were spot on. Thanks to all who replied.
Out of curiosity and knowledge seeking, if undergassed I assume the BCG is not going far back enough for proper functioning. This would explain why the empty case didn’t eject. But apparently the BCG went back far enough to pick up a fresh round from the mag to try to feed. Can someone explain the dynamics of this, which I assume the term is “short stroking?”
Also, can anyone give additional guidance on how to change out the gas rings as they look real delicate.
The gas ring test is common knowledge for most. For ring removal, a drop of lube on rings and just work them off the bolt. Reverse procedure to install new rings. Ring gap does not have to be staggered.
AlphaKoncepts
06-10-13, 12:15
You posted twice that the extractor spring is brand new. When ever new parts are installed and failures occur it makes me think the new part is at fault. Try a different bolt assembly or BCG to see if this eliminates your problem. If it does I'd switch extractor springs.
I finally got to shoot my sick AR today. Delays due to scheduling or bad weather. I brought an extra Colt upper with BCG, H and H2 buffer with springs.
The new replacement gas rings did the trick. Another shooter to my right said the ejection looked positive and consistent. All brass landed in the same pile at around 4 to 5 o'clock.
I used the same ammo (200 rds S&B 55gr yellow/green box) as when the problem first came up to try to replicate the same conditions, but this time with new gas rings.
I also tried what I consider weaker ammo (PMC 55gr Bronze) and all went well.
I did have one ammo issue with the S&B, which I never had before with this lot. I had a single failure to eject. Yes, this time it was truly a FTE. When I pulled the charging handle, the empty case refused to eject. It would not come out by hand. I used a small elbow allen wrench and flicked it out with almost no force.
The primer was dislodged (fell out into the upper and was removed) and the case at the base near the rim was bulged in a circular fashion. Is this termed an "overpressured" round? Did I escape a close one? I have had popped primers before but never with a bulged case.
I checked the bolt group and insured my bore was clear and resumed shooting with no other problems.
BTW, was my original gas ring condition termed "short stroking?" I want to get my terminology correct.
Overpressure. I had some S&B from a few years back and markm and I noticed with also blowing primers as well. He pulled it down and reloaded it.
I finally got to shoot my sick AR today. Delays due to scheduling or bad weather. I brought an extra Colt upper with BCG, H and H2 buffer with springs.
The new replacement gas rings did the trick. Another shooter to my right said the ejection looked positive and consistent. All brass landed in the same pile at around 4 to 5 o'clock.
I used the same ammo (200 rds S&B 55gr yellow/green box) as when the problem first came up to try to replicate the same conditions, but this time with new gas rings.
I also tried what I consider weaker ammo (PMC 55gr Bronze) and all went well.
I did have one ammo issue with the S&B, which I never had before with this lot. I had a single failure to eject. Yes, this time it was truly a FTE. When I pulled the charging handle, the empty case refused to eject. It would not come out by hand. I used a small elbow allen wrench and flicked it out with almost no force.
The primer was dislodged (fell out into the upper and was removed) and the case at the base near the rim was bulged in a circular fashion. Is this termed an "overpressured" round? Did I escape a close one? I have had popped primers before but never with a bulged case.
I checked the bolt group and insured my bore was clear and resumed shooting with no other problems.
BTW, was my original gas ring condition termed "short stroking?" I want to get my terminology correct.
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