AR help- Failure to eject fired cartridge and failure to chamber fresh round from the mag

[superduty]

I've got a build that I got some time ago that's giving me fits. Maybe you guys can help me figure out what's up with it. 

I bought the rifle from another guy locally, and it did fine. I decided to change out the handguard to a YHM one, with a low profile 
YHM gas block. As I remember (this started last year), it worked fine then too. Until the middle of one range trip when it decided it was a bolt gun instead of an AR. 
It suddenly stopped ejecting the spent cartridge and picking up a new one. You can fire it one round at a time by cycling through with the charging handle, 
but it won't function in SA. 

I swapped out BCG's with another, known working carbine, and nothing changed. Same problem. So I guess I can count that out- extractor, etc. 

Does this sound like a gas issue to you all? The gas block is tight to the barrel, but I can't figure out what else might be causing the issue. 

Appreciate your $.02....... 

Thanks

[Ted S.]

Undergassed maybe? Did you change the brand or type of ammo?

[Raoul]

Undergassed maybe? Did you change the brand or type of ammo?

Yeah I'm curious about the ammo too.

[gregintenn]

Did the gas tube somehow work it's self loose from the gas block? Trash in the gas block/tube? Russian ammo?

[Chucktshoes]

It sounds like a gas issue to me. As in no gas. If it is not even attempting to eject, it is getting little to no gas. I have a sneaking suspicion that gas block to port misalignment is the issue. Is it the set screw gas block? The gas block may have shifted and if it is hidden under the handguards, you may not have noticed.

[klamb5]

Has the gas block moved any it doesnt take much .

[superduty]

The gas block moving may well be the issue. It is the set-screw type, under the handguard. I'll do a triple-double check and see if I can determine that.

I'll also scrub the gas system out when I disassemble it.  I was suspecting this (gas) was the issue, but wanted to test the waters before I tore the thing down.

 

The ammo has all been brass through this carbine since I got it- Remington UMC or American Eagle, for the most part.

 

Thanks for the tips guys-  I'll let ya'll know what I figure out.

 

 

FWIW, I have another (different) carbine that I shoot steel cased Russian junk through all the time-  it just eats it up.  I dunno.  :shrug:

[lshel]

Sounds like gas block as loosened and gas port of barrel and gas block are out of alignment.

[Dolomite_supafly]

This is why I do not loke the set screw versions and prefer the clamp on types. I have seen several of the setscrew types work loose and this is especially so with barrels that do not have dimples.

 

One more thing is if the barrel had standard handguards originally then the handguard cap thickness needs to be taken into account. It normally runs .040" thick so if you but the gas block up against the shoulder without taking that into account then you will likely block a portion of your gas port.

 

I would also check the end of the gas tube that goes into the carrier. It can wear over time and this can reduce the seal.

 

My bet is the gas block worked loose and moved.

[superduty]

So, it's been a while since my original post, so I thought I'd give an update.  I took the handguard off, as well as the gas block and tube. I cleaned everything and re-assembled. The first time I took it to the range a couple of weeks ago following this, I fired about 70 rounds, and had one FTE and resulting jam.  Today, I took it out, uncleaned from the last trip, and put 80 rounds of AE brass .223 through it without a single hiccup.

 

I guess that the gas system was the culprit in my initial failure- I'm a bit confused why it would have had a FTE on the first trip after reassembly though. Maybe just an anomaly-  some weird ammo statistical dud- who knows.

 

Since the original post, I've gotten Go / No Go gauges, and will check that. Otherwise, I think it will be an issue of checking the low-pro gas block for tightness from time to time.

 

If I have anything incredibly useful to add to the thread as I go along< I'll add to the post. Thanks all!