Calling all AR-15 Gurus! FTE/FTF issues.


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primalmu
November 10, 2012, 11:07 PM
Hey guys, I'm posting this because I'm having some issues with my AR-15 build. First, some specs:


Spikes lower
YHM Entry Level 20" complete upper
CMMG LPK
Olympic Arms full length buffer tube
UTG A1 stock, spring, and buffer
Magpul 30rnd mags, NHMTG 10rnd mag, and D&H 10rnd mag


So, I took the rifle out to shoot for the first time today. I was shooting PMC .223, and nearly every round I suffered a Failure to Extract/Eject and/or Failure to Feed. Most of the time the spent casing remained in battery as the bolt attempted to shove it up its arse. It also only held open on empty maybe twice.

My initial thought was that the UTG buffer spring must be out of spec, however I had the exact same issues when I swapped the lower from my Del-Ton carbine.

Something is causing my rifle to FTE and short-cycle.

So here's what I've done so far:


Complete tear down and clean
Inspected ejector - appears to be within spec, not dull
Inspect bolt gas rings - gaps not lined up, cleaned and lubed it up after inspection
Applied liberal amounts of lube to all wear points
Checked gas block to see if it was loose - not loose


I should also note that the ejector seems to function fine. Occasionally it won't double feed, but it seems like the bolt isn't slamming all the way forward. When I drop the mag, pull back the charging handle, and let the bolt slam forward, it will extract and eject the spent casing with no problems at all.

I have not yet checked for obstructions in the gas tube because I don't have any pipe cleaners at the moment.

So, what other suggestions do you all have for me to check?

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taliv
November 10, 2012, 11:14 PM
make sure there's a sufficient opening for gas to flow through the gas tube and block. take a can of brake cleaner or similar and stick the little plastic straw into the gas tube, while holding the barrel over something to catch the run off. when you squirt the fluid into the gas block, you should see a substantial flow out the end of the barrel. if you just see a trickle, that may be your problem.


when you hand-cycle the action, do rounds feed and extract and eject ok?

remove the BCG from the action. pull the bolt to full extension. stand it up, with the bolt down. if it collapses, you need new rings.

is the carrier key loose? blocked?

primalmu
November 10, 2012, 11:20 PM
Thanks for the suggestions, I'll check the gas tube tomorrow if I can.

Yes, it feeds and extracts fine when hand cycled.

The gas rings I plenty tight enough based on how it felt placing the bolt back into the BCG.

Carrier key isn't loose, but I'll check to see if its blocked.

HDCamel
November 10, 2012, 11:35 PM
Pictures maybe?

primalmu
November 10, 2012, 11:42 PM
Of what exactly?

HDCamel
November 10, 2012, 11:50 PM
The action after a malfunction, the ammo that misfed/misejected. Anything involved really.

primalmu
November 10, 2012, 11:54 PM
If I'm still having issues after looking things over I'll take some pictures.

cfullgraf
November 11, 2012, 12:09 AM
Like taliv said, I would do a thorough check of the gas system. There is a leak, restriction, something out of alignment (another form of restriction), or something not installed in the correct orientation that is causing the short cycling.

I doubt ammunition is the issue, but if you have a different type, i would rule it out as well.

primalmu
November 11, 2012, 12:31 AM
I forgot to mention that I tried some Wolf ammo to see if that was the issue. No change.

M1key
November 11, 2012, 12:35 AM
Try some NATO pressure ammo...like Winchester Q3131 or Federal XM193.

You would not be the first one to have cycling problems with PMC...or Wolf.

M

madcratebuilder
November 11, 2012, 06:36 AM
Your Wolf and PCM are not up to NATO power levels. Your are under gassed and using under gas ammo so it compounds the problem. Test with some 5.56 NATO, M193 or M855. Check gas block alignment, the barrels gas port many by particularly covered.

Don't put pipe cleaners in the gas tube.


remove the BCG from the action. pull the bolt to full extension. stand it up, with the bolt down. if it collapses, you need new rings.

The gas ring test is done by placing the bolt UP. The rings must support the weight of the bolt not the carrier. You can find this in the 23&P page 3-18.

4. Check bolt assembly (5) for proper fit with bolt
cam pin removed Turn key and bolt carrier
assembly (61 and suspend so the bolt assembly
is pointed down
NOTE
The bolt assembly must not drop out If
weight of bolt assembly allows It to drop
out of key and bolt carrier assembly,
replace bolt rings (p 3-21)

dprice3844444
November 11, 2012, 06:47 AM
you need heavy duty extractor spring and donut.should be the first thing you do on any ar15
http://www.brownells.com/rifle-parts/extractor-parts/extractors/ar-15-m16-extractor-upgrade-kit-prod24635.aspx

ac6916170
November 11, 2012, 07:07 AM
It's a mag issue if it works fine without the mag. Check the feed lips or try different mags

highlander 5
November 11, 2012, 08:49 AM
I'm not an AR expert but on reading this thread I remember years ago that a fellow at my range had similar problems.Long story short,his gas tube was too long and the bolt peened the tube shut and thus no gas to operate said system.

primalmu
November 11, 2012, 03:25 PM
Alright, I checked the gas key and the gas tube. Neither are clogged with anything. I think the next step is to get some Federal XM193 and see if it cycles with the hotter ammunition before taking off the gas block.

the count
November 11, 2012, 08:11 PM
My question is...did the gun ever shoot correctly or was this the first time at the range? Since you put this together with parts from several vendors its not going to be easy to figure this one out. Could be anything from the magazine to the extractor to the gas system....Sorry for the bad news. You might have to take this one to a good gunsmith. My other question: did you check if the rifle is head-spacing correctly?

The culprit can also be one or more parts out of spec. Happened to me recently with a after market bull barrel for my 10/22. After installing it I had all kinds of intermittent FTF/FTE. Tried different ammo, some worked better than other. But never could get 100 rounds out without a problem. Got a KIDD bolt with a heavy duty firing pin, changed springs, etc etc. In the end (it was a very long story) I sent the barrel back to Shaw, and low and behold, the barrel was out of spec and I got a new replacement. Gun works like a charm since.

helotaxi
November 12, 2012, 07:40 AM
Another problem that I've seen several times is insufficient lube. Wet the BCG down with a quality gun lube and see how it runs. You'll need less lube as it wears in a little but initially I've yet to find one that doesn't have problems when on the dry side. That will address most short stroke issues on a new rifle.

Of more concern actually is the fact that it's leaving the spent case in the chamber. That actually points to the rifle being over gassed, not under. It's pretty unusual for a 20" AR to have over-gas issues. That points to something else as the culprit. You said that you tried you Del-ton carbine lower, I'm assuming with a carbine stock? What buffer weight is in that lower? You also mention that the bolt doesn't seem to close all the way. That points to either a dirty chamber, undersized chamber or crud in the locking lugs. I'd actually suspect the first two because they would also explain the extraction problems.

Hunterdad
November 12, 2012, 07:54 AM
I had the same issue when I did my first build. Turns out, I was given a buffer spring that was way too long. I cut it and all was good.

benEzra
November 12, 2012, 07:59 AM
What weight buffer are you using?

rbernie
November 12, 2012, 08:02 AM
Most of the time the spent casing remained in battery as the bolt attempted to shove it up its arse. Does this mean that the extractor didn't extract the spent brass from the chamber?

Taurus 617 CCW
November 12, 2012, 08:08 AM
Another problem that I've seen several times is insufficient lube. Wet the BCG down with a quality gun lube and see how it runs.

This is the #1 problem why AR's short cycle. Most people don't lube enough. I just fixed one for a customer last week that had this exact problem.

taliv
November 12, 2012, 09:18 AM
a clean AR should be able to run a couple hundred rounds with no lube. if it doesn't, that probably means you have or or more small problems that are stacking and you're on the edge of failing

Ramone
November 12, 2012, 09:19 AM
If I am reading correctly, this is a brand new rifle.

IMX with ARs things being a little stiff/tight when brand new makes for some trouble in cycling.

This can often be resolved by using full power ammo (I recommend Federal LC M855) and over- lubing for the first 200-300 rounds.

TITAN308
November 12, 2012, 11:26 AM
As I am sure has been mentioned, almost all FTE or FTF issues I have seen with AR platform rifles ended up being gas related.

I recommend to everyone the very first upgrade to an AR platform rifle is an adjustable gas block. I've yet to see any gas related issues arise once one of these are in place.

MistWolf
November 12, 2012, 11:36 AM
FIRST thing to do is test the rifle for proper function with the ammo. Place an empty mag in the mag well and pull back the charging handle to ensure the mag will lock the bolt back. Next, make sure the BCG is properly lubed, place a single round in the mag, load the rifle and fire. The bolt should lock. It it doesn't it's likely to be a gas problem either from weak ammo or a leak in the rifle or both. It's best to start this test with full pressure 5.56 ammo

chad1043
November 12, 2012, 11:52 AM
If this is a brand new gun, take out the bolt and clean the crap out of the chamber with a brass brush and cleaner. I mean really clean it and then get it nice and lubed up. I had the same problem with Wolf and I did that. It helped a lot. I switched to Hornady .223 and it works just great. Good luck.

primalmu
November 12, 2012, 05:12 PM
Thanks guys. I'll keep all this in mind. I might be able to hit the range this week sometime and give it a test with full power ammo.

WinThePennant
November 12, 2012, 05:43 PM
I might have missed this, but what is the length of the gas system?

redneck2
November 12, 2012, 07:27 PM
I had a SOCOM that would not cycle. Tried different loads, bullet weights, spring work, mags. Did everything but the obvious. Finally just lubed the crap out of it and it's functioned fine ever since.

d2wing
November 12, 2012, 08:02 PM
My guess is a heavier buffer. If the gun is over gassed or the mid or carbine length gas tube it cycles too fast. If so you may need an upgraded extractor.

michael5446
November 12, 2012, 08:37 PM
polish the feed ramps and make sure there are no sharp edges, if the ramp/action damages the brass you will have feed problems...

primalmu
November 12, 2012, 08:43 PM
WinThePennant, it has a rifle length gas system.

WinThePennant
November 12, 2012, 08:54 PM
Run the o-ring.

awgrizzly
November 12, 2012, 10:33 PM
Fail to extract? And fail to feed maybe short cycling? I suppose the latter can relate to the former, if there is a lot of resistance to extraction there may not be sufficient power left to full cycle, it may not be gas related. That can happen with steel cases... you are using brass, right? Something can be causing the cartridges to stick in chamber after they expand from firing. Normally the cases expand to fill the chamber and then bounce back to be loose for extraction. Steel cases don't bounce back which is why they are coated with lube. If the chamber is tight, isn't smooth, or has a deformity the cases can stick.

If the bolt sometimes doesn't want to close it may be this resistance to chambering the cartridge. With magazine in place it may be aggravated by more resistance. Bear in mind that bolt carrier needs to slam shut, the charging handle lock can prevent the bolt from just sliding shut gently.

Have you inspected the spent cases? Look for deep scratches or gouges, signs of pressure expansion like a bulge, and especially check around the case rim for torn brass where the extractor ripped free of the case rim. Look for pieces of brass under the extractor, and look for evidence of extractor malfunction, chips or breaks. These can also result from over pressure so try other barns of cartridges as others suggested (maybe not all PMCs are all that precise). Check extractor function and that the spring is strong and there is a nylon insert inside spring to tighten it all up, even better a nylon ring around it. If you have another AR consider swapping the bolt carrier assemblies to eliminate extractor failure.

Check closely inside chamber for obstructions or roughness. Try to see down in throat if there may be a piece of previous case throat lodged in there. Can you slide a shell all the way into chamber and pull it out without much resistance? What can be happening is case expands and sticks in chamber just long enough that bolt rips extractor free before case bounces back in size... but I wouldn't expect this in a rifle length gas system as it would take longer for the bullet to reach the gas port thus taking a bit more time before bolt extracts case.

You may have gotten an out of spec chamber. Just thinking

the count
November 13, 2012, 10:26 AM
Thanks guys. I'll keep all this in mind. I might be able to hit the range this week sometime and give it a test with full power ammo.
You built this gun yourself, right? You know what headspace is? If thats off, you have a potentially dangerous gun.

PS Just re-read your OP. The bolt, bolt carrier, barrel, etc was bought as a unit? then dont worry about headspace.

You should simply take the gun to a good gun smith if you have one in your area. He might charge $30-50 to look it over just to make sure its not something obvious (to him, not to you) and that its basically safe.

chrome_austex
November 13, 2012, 10:41 AM
Check the gas port in the barrel to gas block alignment, that sounds like the most likely culprit. While the gas block is off, check and make sure its not clogged or defective.

Make sure the carrier is well lubed and try a PMAG if you haven't. (I've got a gun that runs great, but double feeds with steel mags and steel cased ammo)

If the gas port is in alignment, the carrier moves freely, and you're using full strength brass cased ammo out of a PMAG, then I'd be looking hard at the buffer setup.

primalmu
November 13, 2012, 08:35 PM
@awgrizzly: Thanks for the suggestions, I'll definitely reference your post as I troubleshoot further (which like I said earlier will depend on when I can get to the range). I've also got a Wolff HD extractor spring and some o-rings on the way. Oh, and I used primarily brass ammunition, although I did run some steel-cased through it while trying to troubleshoot. No change in function between the two.

@the count: Yes, I bought the upper complete. BTW, in my reading there seems to be a controversy over headspacing in ARs. Some seem to say that the AR design automatically headspaces itself (also asking the question of what adjustments would you take to adjust the headspace of an AR as further evidence), while others say that they in fact do need to be headpaced. I will look into this further.

@chrome_austex: I did try a PMAG and had the same issue. Admittedly, after I cleaned my AR I realized that the BCG wasn't well lubed. I'm hoping that this is the source of my problems. Rest assured, it is lubed up good now and is awaiting another trip to the range.

Redlg155
November 13, 2012, 09:35 PM
Headspacing can be checked by a set headspacing guages, a relatively easy process. The majority of folks don't worry about it when using a NEW bolt. However, swapping a used bolt can lead to problems. In addition, headspacing requires a set of specialized tools and knowledge to do it right. Definitely not a task for a "unit level" armorer.

It definitely sounds like a gas problem. I know it sounds strange, but I wouldn't rule out a gas tube installed upside down.

helotaxi
November 13, 2012, 10:03 PM
The headspace is either in spec or it isn't with an AR. You can't change it or adjust it once the barrel chamber is cut and the barrel extension attached. It being out of spec also isn't going to cause the problems you're describing.

MistWolf
November 16, 2012, 09:50 AM
My guess is a heavier buffer. If the gun is over gassed or the mid or carbine length gas tube it cycles too fast. If so you may need an upgraded extractor.

Rule 9- No matter what type of malfunction a shooter is having with an AR, someone will suggest the rifle is over-gassed before the thread reaches Page 3

chad1043
November 18, 2012, 08:33 AM
Any update?

primalmu
November 18, 2012, 10:01 AM
Not yet. Right now I'm at the mercy of other people's club memberships, haha. Might be able to hit up a range on Friday though.

primalmu
November 23, 2012, 05:16 PM
Okay, finally got back out to the range. I put 60 rounds through my rifle without any FTEs or double feeds. Between cleaning the rifle, a liberal application of lube, a heavy duty extractor spring, and an extractor spring o-ring, the rifle operated nearly flawlessly. The only issue I had was a single failure to remain open on empty (out of about 10). Not a big deal and I figure it will sort itself out as I break the rifle in.

chad1043
November 23, 2012, 06:12 PM
Good news. Glad it is working.

primalmu
November 23, 2012, 07:22 PM
Oh yea, it ran milspec 5.56 NATO as well as .223 Rem perfectly.

Mr.Davis
November 23, 2012, 08:26 PM
1) Lube the heck out of the BCG and go shoot some full-power 5.56 ammo. Your FTE issues are due to insufficient gas pressure. Your FTF issues have the same cause: the BCG isn't traveling back far enough to strip the next round off the magazine.

2) If what I described doesn't work, you have a problem in your gas system. Check to see if your gas keys are properly staked, that your FSB is pinned and straight.

EDIT: I see that the full-power ammo sorted out most of your issues, but you had one failure to lock back. That's still symptomatic of a leaky gas system. I suggest you look at my point 2 above.

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