FTE on AR-15 upper chambered in 223/5.56

[ghettoblaster]

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.

[ray1970]

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

[ghettoblaster]

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

[Delfuego]

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

[Lurch]

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

[ghettoblaster]

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.

[Lurch]

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?

[ghettoblaster]

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....

[Delfuego]

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...

[BPTactical]

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.