FTE on AR-15 upper chambered in 223/5.56

hey all,

Just recently built an AR-15. This is the second build that I've done. However, I'm having an issue with FTEs. I can cycle rounds through it just fine with I'm not firing. Everything seats well, ejects well, and seems to flow rather smoothly. However, when I go "hot" with it I have a double feed issue after the very first round. Again, this doesn't happen when I'm just cycling rounds/snap caps through it without firing. I thought it might be overloading the magazine causing it to push a bit too hard on the top cartridge, but this time I even tried it with only three rounds in it. It's done this with both Tapco and Magpul PMAG magazines.

Any suggestions out there? This is getting rather frustrating.

Thanks.

So, just to clarify.... You fire a round, it ejects, and two fresh rounds seem to be battling for a spot in the chamber?

Sorry, guess I wasn't clear. The round fires, DOESN'T eject, and then the next round presses it in further, jamming the barrel.

What type of ammo is very important. (steel vs brass vs reloads)

What barrel? Sounds under gassed to me. With the mag in and only one round fired will it lock back?

I haven't tried the one round approach yet. but I've used both new Winchester 5.56 rounds and TulAmmo (yeah, I know) and neither has worked. 16in barrel, chrome lined. Is there anything about the lower that would cause this to go bad? Friend of mine has the same upper and no problems.

Switch uppers with your friends and see if it does the same thing. The only thing I could think of in the lower would be a real stout spring/buffer or something is binding up causing it to short cycle. But if you can cycle rounds by hand through it I would think you would notice something.

Did you buy the upper complete or did you build it?

The upper I bought complete, although I can't remember the name of the place that made it at the moment.... I'd have to look it up. And I've wondered about the buttstock but it's the same as my other one....

I had similar issues with steel cased ammo in one specific upper with a tight chamber, issue disappeared with brass.
Check the used brass for extractor marks, case deformation or bulges.

Have you tried to clean the chamber & lube the heck out of the BCG?
Check the extractor also; I use the upgrade extractor spring on all mine.

Does the bolt hold open on the last round? That could rule out under-gassed.

Try a GI mag if you can get one, just to eliminate a mag failure.

Worst case scenario, take it to BP tactical or Bowers and they will cure it...

Short stroke or extractor issue typically. Make sure your extractor has correct tension and install an upgrade kit. Make sure it engages the rim correctly, I have seen a couple of late that the groove on the extractor was too shallow.
Short stroke-check the gas port/gas block relationship, gas port size, gas key/ rings for leakage.
Check to make sure you have the correct buffer/spring for your application be it rifle or carbine.
Check your brass for indication of gouging from a rough/burr in the chamber.
+1 on the single shot test.
Don't hesitate to come see me if you aren't comfortable or baffled by something.

I'm not sure if the bolt will hold open or not since I've only tried it with other rounds in the magazine.....Always FTE's and then jams when trying to feed the next round into the chamber since the casing didn't eject. I may switch out the upper onto my other lower that I know works well. If anything, I think the short stroke is probably the issue.... I don't quite trust the buffer or spring for some reason. The BCG and chamber are fully lubed.

No gouging on the casing, either. Like I said, I can chamber rounds and eject them just fine. It's only when ejecting spent casings during test fires that I have issues. Leads me to believe the issue lies elsewhere.

BPTactical: where are you located? I may need a second set of eyes on this thing.

Thanks all for your help!

Quote:

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Originally Posted by ghettoblaster

I'm not sure if the bolt will hold open or not since I've only tried it with other rounds in the magazine.....Always FTE's and then jams when trying to feed the next round into the chamber since the casing didn't eject. I may switch out the upper onto my other lower that I know works well. If anything, I think the short stroke is probably the issue.... I don't quite trust the buffer or spring for some reason. The BCG and chamber are fully lubed.

No gouging on the casing, either. Like I said, I can chamber rounds and eject them just fine. It's only when ejecting spent casings during test fires that I have issues. Leads me to believe the issue lies elsewhere.

BPTactical: where are you located? I may need a second set of eyes on this thing.

Thanks all for your help!

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I would throw another buffer and spring combo in it see if it helps
bert is in Thornton I am in Stapleton if you want someone else to look at it a little closer

Unfired rounds are not fireformed to the chamber, that is why they hand cycle ok.
What makes you doubt the buffer/spring?

Hell. I like to play guessing games. Here's my guess.... Chamber problem.

Either rough inside, cut incorrectly, or maybe a burr or something.

BPT - I had some trouble with the buffer/spring while I was putting it together. Took me till I disassembled it and put it back together before I felt even mildly comfortable with it.... I'll have to play with that a bit and see. But from the posts on here I think I may have to do a bit more digging on the upper and see if the gas tube is getting enough pressure too.

I'm actually kinda enjoying learning more about this now that it ain't quite working right. However, it would have been nice to have it fully functional last weekend at the range :(

Ray - thanks for the suggestion! Would a fired shell casing operate differently than a non-fired shell casing? The unfired ones are cycling great..... perhaps I should bring out the ole magnifying glass and take a closer look, though.

I would also pull the gas block and check to see if the gas mark is indeed centered on the hole on the gas block. Then you can also check to see if there is anything in the gas port. I will be in Aurora tomorrow I could swing by and take a look.

Quote:

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Originally Posted by ghettoblaster

Ray - thanks for the suggestion! Would a fired shell casing operate differently than a non-fired shell casing? The unfired ones are cycling great..... perhaps I should bring out the ole magnifying glass and take a closer look, though.

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See post 10 and 13.

RayRay sloooow[Sarcasm2]

Hey, who moved my Cheetos? I could have sworn they were right here.

Quote:

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Originally Posted by ray1970

Hey, who moved my Cheetos? I could have sworn they were right here.

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Look in your other hand...........

So last night after logging off, I started to take apart the upper and what do I find? A piece of broken shell casing in the area outside the chamber. This was from the first FTE that I experienced from a month or so ago. The casing was brass and part of the butt of the casing next to the primer broke off. That may not be 100% of why the extraction process didn't work as well as it should, but it may be part. I'm going to do some more investigation after work today checking gas block and port.... BPT I'll let you know what I find. If I'm still stumped, I'll definitely have to pay you a visit.

Thanks again for all the help!

Quote:

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Originally Posted by BPTactical

Look in your other hand...........

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Ahh... There they are.

Thanks.

[Beer]

Quote:

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Originally Posted by ghettoblaster

So last night after logging off, I started to take apart the upper and what do I find? A piece of broken shell casing in the area outside the chamber. This was from the first FTE that I experienced from a month or so ago. The casing was brass and part of the butt of the casing next to the primer broke off. That may not be 100% of why the extraction process didn't work as well as it should, but it may be part. I'm going to do some more investigation after work today checking gas block and port.... BPT I'll let you know what I find. If I'm still stumped, I'll definitely have to pay you a visit.

Thanks again for all the help!

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This sheds a bit of light on the subject. There are a few things we need to check.
Headspace-excessive headspace can cause a casehead blowout and it can also bulge the case sufficiently enough to cause extraction issues.
Extractor condition, although if it is gripping sufficiently to pull the rim unlikely.
Chamber-if it has any annular machine marks or roughness they can grab a case to the point it won't extract.
Gas pressure-an over gassed gun can cause the issue you are having for a couple of reasons:
If the gas pressure is too high when the unlock/extraction cycle starts the case is still firmly expanded in the chamber and can stick the case.
Insufficient headspace can crowd the round into the rifling, causing a pressure spike similar to an overgassed situation and give the same result.

When the empty case was left in the chamber did it extract by hand easily or did you need to knock it out with a cleaning rod?

It is entirely possible that the chunk of casing was retarding the bolt unlocking and throwing the timing off which could cause the issue as well.

Wow, I used the word "retarding" in a totally legit and coherent manner..........

BPT - I had to use a cleaning rod to knock it out in both cases (brass casing and steel casing). When I found the chunk of casing, it was crammed to the rear of the chamber head space which may have been crowding the round into the rifling as you say. Would you say the best way to test this theory is to fire it again, one round at a time, or is there a better method for assuring that everything is set up properly?

I would try the single round method for a few shots-Single round from the mag and see if you:
1-get clean and consistent extraction.
2-bolt locks back as intended.

Use a standard GI metal mag, they always work. Some rifles have shown issues with Pmags and Tapco, well they are Tapco mags.

Save your brass and inspect it for any anomalies.

If all seems well step up your mag load to 3 rounds and see how she runs. If all is well let her run, if not come see me.

Hey BPT - just got back from the range. Here's my observations:

1) The round fires, the bolt locks back, but the casing does not eject. Had to use a cleaning rod to push it back out.
2) When I finally get the casing out, I can tell that the extractor ripped off/sheared the rim of the casing. So perhaps it's only stuck in there because it's getting yanked so hard it snaps the rim.
3) After that I switched lowers and put it on the other that I built which I had just used and I know works. In this case, it worked flawlessly: round fired, case ejected, bolt locked back, no problems at all.

So I'm starting to think maybe the buffer spring isn't strong enough on the buttstock. When I compare the pull on both rifles, the one with the problems seems a bit lighter to me. Lighter spring = faster action = sheared casing rims? That's my theory. What else could it be and how can I test it?

At least I know the upper works fine. Handled the round like a champ and plenty accurate. Bad news: may need new parts on the lower.

Suggestions?

One thing I don't think we ever established. Rifle or carbine?
Check for the correct spring.

From:
TECHNICAL MANUAL
ARMY NO. 9-1005-319-23&P
AIR FORCE TO 11W3-5-5-42

RIFLE: 11 3/4 Inches (29 85 cm)
minimum to 13 1./2 inches (34 29 cm)
maximum

CARBINE: 10 1/16 inches (25.56 cm)
minimum to 11 1/4 inches (28.58 cm)
maximum.

What weight buffer if a carbine, should be an H or H2.

Carbine, 16 inch barrel. I'm thinking maybe I ought to replace the entire butt stock (cause it's fun anyway!). But before I do, is there anything else I'm missing that might possibly be wrong?