AR-15 won't extract UPDATE: Fixed

[Parker]

so in my research i found this article.....http://www.ar15barrels.com/prod/operation.shtml

With this part being of interest......
"Now for extraction, the WRONG ways.
First, too much gas(most common):
The bullet has not left the barrel yet, but it's past the gas port.
Too much high pressure gas is rushing into the carrier, causing it to move rearward faster then desired and unlock the bolt from the extension.
Pressures are still high so the cartridge case is NOT ready to be extracted yet.
The carrier's momentum continues to pull backward, but the pressures in the case actually hold in in the chamber.
This causes a hiccup in the carrier's momentum.
Depending on the severity of the timing, several things can occur:
#1 The (weak) extractor spring allows the extractor to jump over the rim of the cartridge and the bolt carrier continues rearward, grabbing the next round and causing the classic "fired case in chamber, live round behind it" FTE.
The brass shavings under the extractor usually contribute to this one as well."

if that is what's happening, how do you combat that. Adjustable gas block, heavier buffer?

 

[mtdawg169]

so in my research i found this article.....http://www.ar15barrels.com/prod/operation.shtml

With this part being of interest......
"Now for extraction, the WRONG ways.
First, too much gas(most common):
The bullet has not left the barrel yet, but it's past the gas port.
Too much high pressure gas is rushing into the carrier, causing it to move rearward faster then desired and unlock the bolt from the extension.
Pressures are still high so the cartridge case is NOT ready to be extracted yet.
The carrier's momentum continues to pull backward, but the pressures in the case actually hold in in the chamber.
This causes a hiccup in the carrier's momentum.
Depending on the severity of the timing, several things can occur:
#1 The (weak) extractor spring allows the extractor to jump over the rim of the cartridge and the bolt carrier continues rearward, grabbing the next round and causing the classic "fired case in chamber, live round behind it" FTE.
The brass shavings under the extractor usually contribute to this one as well."

if that is what's happening, how do you combat that. Adjustable gas block, heavier buffer?

A cash refund and acquisition of a quality barrel. The primary cause of the issue described above is an over sized gas port. No fixing that, just have to live with it and try to patch the symptoms with heavier buffers, better extraction parts, springs, etc.

 

[WMSproject]

I did notice that some brass is being shaved off the rim of the case. That could be caused by one of several things. The most obvious would be that the timing is off on the rifle, causing the bolt to be blown back before the pressure inside the case has dropped to a level where the case can be extracted from the chamber. The chamber might not be machined to spec, the head spacing might be off, the gas port might be too close to the chamber.

Another cause might be that the extractor is shaped wrong and it is slipping off the case rim when the bolt is opening. I would recommend putting a different bolt from a working rifle in and see what happens. The problem is most likely the first thing I mentioned. This does happen with Short Barrel ARs when using Steel Case ammo quite frequently.

 

[Parker]

Email I sent this morning…

Jay,


I've been researching all the possible causes of an AR not extracting. I've pretty much come to the conclusion that the rifle is over gassed, causing the timing to be off. Upon closer examination of the spent brass you can see on the back of the casings where the brass has been stretched due to trying to be extracted while there is too much pressure in the chamber. And the gouges in the brass rim from the extractor slipping.


From my reading this is most likely caused by an over-sized gas port. And a new barrel is the recommended fix, anything else is just treating the symptoms and not the problem. Do you have any other barrels?


Do you know of anything else that could cause these problems? I do not want to just beef up the extractor because of the stretching that is taking place on the casings. I was saving the brass to reload (someday), so I do not want to start with deformed cases.


If you do not feel you can fix the issue in a timely manor I would like to return the upper for a refund.


Thank you for your time,
Anthony

 

[mtdawg169]

Email I sent this morning…

Jay,


I've been researching all the possible causes of an AR not extracting. I've pretty much come to the conclusion that the rifle is over gassed, causing the timing to be off. Upon closer examination of the spent brass you can see on the back of the casings where the brass has been stretched due to trying to be extracted while there is too much pressure in the chamber. And the gouges in the brass rim from the extractor slipping.


From my reading this is most likely caused by an over-sized gas port. And a new barrel is the recommended fix, anything else is just treating the symptoms and not the problem. Do you have any other barrels?


Do you know of anything else that could cause these problems? I do not want to just beef up the extractor because of the stretching that is taking place on the casings. I was saving the brass to reload (someday), so I do not want to start with deformed cases.


If you do not feel you can fix the issue in a timely manor I would like to return the upper for a refund.


Thank you for your time,
Anthony

Good job Parker. I have a feeling that Shrek was on to something with the chamber specs though. Either way there's something wrong with the barrel and they should take care of it to your satisfaction.

 

[devin25gun]

Easy way to check for gas block issues is to stick a small piece of vacuum hose inside the upper with bolt out . Put the hose over the gas tube then blow. If air goes thru easy into barrel then it is open. If clogged it will be hard to blow thru with restriction. This only tells you it is clear not if the hole is fully aligned with gas port to gas block.

 

[Parker]

Sky guns is going to replace the upper. I'm happy with that as long as it works. I want to think you guys that responded to this thread, now I know of some things to look for when checking out an AR. Thanks for taking the time to help a newb. I have a stripped lower as well that I'm going to build myself. Hopefully it will be the first of many.

 

[Parker]

Picked up my replacement upper on Thursday. I got a chance to shoot it today. Everything functions as it should. The only issue is it is still a rifle barrel ext on an m4 upper. So that is not ideal but I plan to fix that myself when I build my other lower I'll get a upper with out the cuts and swap this barrel to it and use the current m4 upper for my 300 blk build.

 

[GAAREDSTATE]

Actually, if you look at the "BAD" picture provuded by "Collin", you can see from the picture provided it shows it! looks like you need to take a round file to it and extend the groves.

 

[mtdawg169]

Picked up my replacement upper on Thursday. I got a chance to shoot it today. Everything functions as it should. The only issue is it is still a rifle barrel ext on an m4 upper. So that is not ideal but I plan to fix that myself when I build my other lower I'll get a upper with out the cuts and swap this barrel to it and use the current m4 upper for my 300 blk build.

Parker, I'm glad you got one that will run, but it still concerns me that they are building off of the wrong receiver. Sooner or later, you will have feeding issues depending on ammo selection, magazine wear, etc. It's such an easy thing to fix, I don't know why they didn't take care of it. That is unless, they don't have a supply of M4 cut upper receivers. If that's the case, they shouldn't be selling anything until they can assemble them with the correct parts. I still suspect that your original extraction issue was related to a poorly cut chamber.