Need advise on AR15 FTE issue

[Madball13]

This is a common problem with Stags, i had the same thing happen to mine and i ultimately solved the problem by getting rid of it.

It is most likely the bolt and buffer. My gun would do the same thing after i cleaned it and i came to the conclusion when the gun is clean the BCG moves to fast and there is not enough tension on the extractor to properly remove the case, when the gun gets dirty the BCG slows down.

I would make sure you have the right parts in your bolt. Get this:
http://www.bravocompanyusa.com/BCM-Extractor-Spring-Uprade-Kit-p/bcm extractor spring upgrade.htm

If you built the lower what buffer did you get? If you went the cheap route you should replace it with a H2:
http://www.bravocompanyusa.com/H2-Carbine-Buffer-p/buffer carbine h2.htm

If all else fails get this:
http://www.bravocompanyusa.com/BCM-16-Mid-Length-Upper-Receiver-Group-p/bcm-urg-mid-16.htm

 

[mac67]

I've got this http://palmettostatearmory.com/inde...rts/build-kits/moe-lower-build-kit-black.html. When I placed the order I was told it was a carbine buffer. No where on the buffer is an "H". How much should an "H" buffer weigh vs a Rifle buffer ? Or is it length ?

 

[jasons]

I've got this http://palmettostatearmory.com/inde...rts/build-kits/moe-lower-build-kit-black.html. When I placed the order I was told it was a carbine buffer. No where on the buffer is an "H". How much should an "H" buffer weigh vs a Rifle buffer ? Or is it length ?

Stolen from: http://www.m4carbine.net/showthread.php?t=3967:

Standard CAR 2.9 oz.
H buffer is 3.8 oz.
H2 buffer is 4.6 oz.
Rifle buffer is 5.17 oz.
9mm buffer is 5.5 oz.
H3 buffer is 5.6 oz.

 

[mac67]

thank you jasons/madball

I might be getting closer to an answer. I just weighed the buffer. It's 2.9 oz.........

 

[Madball13]

Did you take your bolt apart? What color is the plastic buffer in the middle of the spring? Does it have a rubber o-ring?

 

[mac67]

Did you take your bolt apart? What color is the plastic buffer in the middle of the spring? Does it have a rubber o-ring?

Do you mean the extractor spring ? If so, no I didn't take that apart.

Update: Just took it apart. 4 coil, no O-ring. There is a small black post in the middle of the spring. felt metal to me tho ?

 

[jasons]

thank you jasons/madball

I might be getting closer to an answer. I just weighed the buffer. It's 2.9 oz.........

For normal ammo that will be fine. You should only need a heavier buffer if you're shooting something hotter. It's not the buffer. Everything you've mentioned indicates that it's an out of spec (too tight) chamber.

If you're near Melrose / Malden, swing by and I'll show you how to check the headspace. That will answer your question.

 

[Supermoto]

Everything you've mentioned indicates that it's an out of spec (too tight) chamber.

If you're near Melrose / Malden, swing by and I'll show you how to check the headspace. That will answer your question.

Yep,

If it won't cycle by hand, then it is not a Buffer/Spring problem. not a gas problem (though I bet it is over gassed) it is the chamber

 

[ThePreBanMan]

I would agree that the chamber would appear to be the suspect. But it COULD also be an out of spec bolt carrier group too. But since you've had rounds actually get stuck in the chamber - and the extractor remove part of the case in the process - the chamber would seem more likely.

 

[mac67]

Just got off the phone w/Stag. It's going back. I'll keep you posted. Thanks for all the help/advise.

 

[Madball13]

I'm thinkin the same thing at this point. I pulled the firing pin, put 3 live rounds in the mag, dropped the bolt. The first round ejected w/a firm pull on the charging handle, 2'nd round stripped off and that was it. The bolt stuck shut. Same deal, muzzle down, 2 hands pulling. Didn't budge. I had to break down the gun a tap out the BCG w/ hammer and dowel. WTF.

ps the spring measures 11" and the gun does hand cycle w/out ammo

I missed this post, sounds like the chamber.

 

[Fixxah]

Just got off the phone w/Stag. It's going back. I'll keep you posted. Thanks for all the help/advise.

Wise choice. Their headache not yours.

 

[smallcircle]

My new 2H is back at Stag as well. Same problem. I had a gunsmith check the headspace and he said it is fine. My spent casings have the same ring at the throat at yours. The smith though that the cartridge is contacting the rifling, which causes a FTE when the cartridge expands on firing. Dummy round cycle fine on mine. Seems like a QA problem at Stag.

 

[Madball13]

Seems like a QA problem at Stag.

Sounds about right.

 

[mac67]

UPDATE: Upper shipped back to Stag 6/18. Arrived 6/19. Got a call today (6/26) from CS confirming that they recvd. it. The person that does the repairs is on vacation....

I was told the approx. turn-around time from today will be 2 plus weeks. That equals almost a month turn-around. Does that sound right ? They have one person making repairs ?.........

 

[RKG]

The is a bit of a SWAG, but I'd bet a reasonable sum (somewhere between a nickel and a quarter) that the chamber was reamed off axis, as a result of which the rounds are getting ever so slightly bent when they are chambered. While other chamber issues suggested (inadequate headspace, burrs, and the like) could be the cause of a jammed case failure to extract after firing a round, I'd be real surprised if any of those problems could cause a jammed case when trying manually to extract a chambered round.

If you have the equipment and skills to do so, see if you can recover one of the loaded rounds that resisted extraction (without firing) and see if you can measure runout at the neck.

 

[mac67]

UPDATE: 7/5/12

Got the upper back today !!. (much sooner than expected) So far impressed w/Stag's response to the problem. The report back was an out of spec., "Tight chamber". Got a new BCG w/a fluff-n-buff. The fit is noticeable better. Range report to follow.

 

[stinx]

My buddy had the same issue with a S&W M&P 15. The recipe to make these things is pretty much established I dont understand why so many companys cant just follow the established plans. It seems everytime an AR maker varies from whats known in an effort to save money problems arise.

 

[jasons]

UPDATE: 7/5/12

Got the upper back today !!. (much sooner than expected) So far impressed w/Stag's response to the problem. The report back was an out of spec., "Tight chamber". Got a new BCG w/a fluff-n-buff. The fit is noticeable better. Range report to follow.

Good to hear that they made it right.

 

[mac1911]

Stag has done me right both times on 2 different issues......they also quoted a long turn around time of several weeks.......1st was 7 days 2nd time was 11 days from ship out to return.

 

[smallcircle]

I just got my 2H back from Stag. They reported they replaced the barrel (too tight), and polished the chamber. I think they replaced the bolt too. Worked flawlessly at the range this weekend.

 

[5pins]

For future reference, taking out the firing pin and then working the action can lead to haveing your BCG stuck in your upper. The firing pin keeps the cam pin from rotating, if it should turn at the wrong time it will not allow the bolt to unlock from the barrel.

 

[mac67]

Finally got to the range. 50 flawless rounds. Paper plate accurate/grouping at 50 yards w/Iron sights. I was short on time, so my next range trip I plan to dial it in.