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Posted: 9/3/2003 6:24:41 PM EDT
[Last Edit: 9/3/2003 6:34:07 PM EDT by Redbone]
While sighting in a new upper with Win Q3131 today, I had a few FTE's.I read the FAQ's and I'm wondering if they were caused from an Olympic X-ring over the extractor spring(too much tension on extractor) or still not enough tension(maybe subpar extractor spring).I've used the X-ring on all other bolts w/o any malfunctions.
Link Posted: 9/3/2003 7:41:43 PM EDT
What is an FTE?
Link Posted: 9/3/2003 8:06:40 PM EDT
[Last Edit: 9/3/2003 8:27:35 PM EDT by Redbone]
Failure to extract.New round would jam into chamber and after magazine was ejected and live round removed,spent round would extract w/o a problem after cycling again.
Link Posted: 9/3/2003 8:50:59 PM EDT
Redbone, I've read your post at least three times now and still can't decipher it. Would you please rewrite it in a clearer manner? I don't see how increasing the extractor tension can lead to FtEx. That can lead to failures to feed/chamber/lock. If you're using the "X ring" then I assume it's an OAI upper. Who built the upper? Has the headspace been checked? Has the chamber been inspected for rings and scratches?
Link Posted: 9/3/2003 9:08:58 PM EDT
Sorry if I'm not being more clear. While sighting in a used CMMG 14.5'DPMS 1/7 chrome-lined upper today, I had about 10 failures to extract out of the 100 or so rounds I fired.What would happen is I would fire a shot and the bolt/carrier would get stuck due to a new round being stripped from the magazine and getting jammed against the spent shell that did not get ejected after being fired.I'm using a new DPMS bolt/carrier and installed an Olympic XRing around the extractor spring.According to the FAQ's a FTE is usually caused by a weak extractor spring.Using the XRing, I thought this wouldn't be a problem.I'm wondering what else might be the cause of the problem.
Link Posted: 9/4/2003 12:10:27 AM EDT
[Last Edit: 5/25/2004 9:47:21 AM EDT by Tweak]

Originally Posted By Redbone:
Sorry if I'm not being more clear.



That's quite alright RB, we all have to start somewhere.


the spent shell that did not get ejected after being fired.


Didn't get ejected huh? Have you checked the tension of the ejector spring? If you're using a Dfender then your extractor tension is about as high as it can possibly go.

There is a synergy between the extractor and the ejector. If the extractor is weak you may get FtEj.

Extraction ends when the mouth of the case leaves the end of the barrel extension. If the case is in the chamber it's a FtEx.
Link Posted: 9/4/2003 9:43:20 AM EDT
Redbone, next step is to examine the fired cases, both those that extracted and ejected correctly, and those that did not. We are looking for a bunch of things: Marks on the case body or neck that indicate a rough or out of shape chamber; Barrel shaped case body; Rim ripped through by the extractor; Chamber issues are best solved by shipping it back to the house that chambered it and present them with the evidence (out of shape cases, measurements, etc.) and having them fix it. Another possible is that the extractor is not running all of the way down into the extraction groove. This can happen because of burrs or dimensional problems in either the bolt or the extractor, or metal chips between the two parts. You can stone off burrs, but dimensional problems are best fixed with new parts. One of my favorite things to do to all autoloaders (for reliabile extraction) is to polish the chamber. Get back to us if you want some ways to do it. This is not a fix for a rough or out of shape chamber... Since this is a shorty, they sometimes do have a tendency to rip off rims and otherwise be driven too hard. If all else fails to fix this, there are large volume gas tubes and the famed Pigtail for slowing down the action, as will ballasting the bolt carrier, but let's make sure that the basics are OK first.
Link Posted: 9/4/2003 2:44:34 PM EDT
[Last Edit: 5/25/2004 9:48:06 AM EDT by Tweak]
It's probably a tight chamber. This link will probably be of interest to you. AR15fan and I are having the same problem with our CMMG/DPMS uppers. I think I've managed to improve the extraction. Billski, I would like your ideas on how to polish the chamber.

www.ar15.com/forums/topic.html?b=3&f=12&t=169340&page=1
Link Posted: 9/4/2003 3:25:38 PM EDT
Thanks for the link.I think we're having the same problems with our uppers.My buffer is getting marred as well.It seems too common to be out of spec lowers.
Link Posted: 9/5/2003 4:19:19 AM EDT
Chamber Polishing – I advocate doing this in Semi-Auto rifles to give reliable extraction. The following is copied from a Word doc. Any questions, respond here. I will repeat - if the chamber is undersized, get it fixed (usually with a NATO spec chamber reamer). A cerrosafe cast of the chamber is a good idea. Some of the good NRA High Power 'smiths do this to ensure reliability and so do I. Chamber polishing is intended to allow a rifle with a well shaped chamber to extract cleanly. Chamber polishing will not fix out of shape chambers, bad extractors, oversized or undersized gas ports, loose carrier keys, small bolt tails, etc. Also, if you have problems with chambering, this is not the fix. If you have other problems, those should all be found and dealt with too. The big thing to remember about chamber polishing is that we are just trying to take the "meat hooks" off the surface. The surface looks sort of like a mountain range, and the high points are sharp. The brass is pressed onto the sharp points, grab the brass, and make extraction tough. We are just trying to knock the high points off, but leave the valleys. We are not trying to change chamber dimensions in any measurable way at all. The next thing to remember is that you should polish the body and you should not touch the throat. In between the body and the throat, there is little advantage to fussing with it and it has risk that you will mess up the throat, so my advice is to stay away from the neck and throat. Several methods are cited by folks on these threads. Some actually recommend JB on a chamber mop turned with an electric or cordless drill. JB is finely divided clay in grease and is well known to be harmless to our pampered bores. It is great for removing copper, carbon and primer ash, and will make the chamber look brighter, but I am skeptical that it will actually take off the high spots in the metal. If your chamber looks better after a scrubbing with JB, it was probably dirty to begin with (which might have been the source of any reliability problems). Some folks use Flitz or Simichrome on a chamber mop. This method is simple and can work. My concern is that most chamber mops can get to the throat. Polish the throat with a spinning mop and abrasives, and you may mess up your throat. Make sure that the mop cannot get beyond the shoulder and you should be OK with this method. A rough chamber will not be fixed this way, and a chrome lined chamber is unlikely to smooth out this way too, but a good commercial chamber can be made to extract slickly with Flitz. My method – Thoroughly clean the barrel and chamber and inspect it. A chamber mirror helps a bunch here. Remember what it looks like for later. Mount a dowel on a piece of GI cleaning rod and sand it to the same taper as the chamber, then split it lengthwise to hold a 1" wide strip of abrasive paper. Trim the length so that the tool will enter the entire length of the chamber body, but it won't go into the neck. I use 220 grit wet-or-dry abrasive. Emery cloth WILL cut too easily and enlarge your chamber. If you want a GI chamber, have the appropriate reamer pushed into your chamber – don't use emery cloth to get it. I like 220 wet-or-dry because once the surface is smoothed down it just does not want to cut anymore. Run the tool on a drill at low speed, with oil, and work it back and forth in the chamber a few times, then clean the chamber and inspect it. You are looking for places that are smoothed out and places that are still as rough as before you started. The rough spots will need more work. A chamber mirror is useful. If you still have rough spots, continue. If the paper starts to load up and look dull, replace it. Follow up by cleaning the chamber and barrel thoroughly, inspect it again and test fire it.
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