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

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primalmu

primalmu

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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?
 
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?
 
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.
 
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.
 
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
 
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.
Click to expand...

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)
Click to expand...
 
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It's a mag issue if it works fine without the mag. Check the feed lips or try different mags
 
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.
 
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.
 
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.
 
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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.
 
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.
 
Most of the time the spent casing remained in battery as the bolt attempted to shove it up its arse.
Click to expand...
Does this mean that the extractor didn't extract the spent brass from the chamber?
 
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.
Click to expand...

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.
 
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
 
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.
 
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.
 
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
 
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