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Posted: 3/12/2014 6:06:40 PM EDT
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Have a franken-build gun I bought from someone, and having an issue. When I fire it, after about 2 or 3 rounds, the previous round extracts but is not ejected, It still hangs in the gun, with the next round being almost stripped from the magazine and fed. Sometimes the spent round will lay in there perfectly straight on top of the next round, or it will stovepipe. I used another bolt with a known good extractor and ejector, and still get the same problem, but I can get about 5 rounds shot before it happens. I have attached a picture of what I am describing (stovepipe). The gas tube is clean, so no blockage there, Any ideas/suggestions?
***I also meant to add that if I put a magazine in it, and cycle the rounds manually, they all extract and eject perfectly. It only does it during live fire.*** 
Thanks! |
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Quoted:
Have a franken-build gun I bought from someone, and having an issue. When I fire it, after about 2 or 3 rounds, the previous round extracts but is not ejected, It still hangs in the gun, with the next round being almost stripped from the magazine and fed. Sometimes the spent round will lay in there perfectly straight on top of the next round, or it will stovepipe. I used another bolt with a known good extractor and ejector, and still get the same problem, but I can get about 5 rounds shot before it happens. I have attached a picture of what I am describing (stovepipe). The gas tube is clean, so no blockage there, Any ideas/suggestions? ***I also meant to add that if I put a magazine in it, and cycle the rounds manually, they all extract and eject perfectly. It only does it during live fire.*** <a href="http://s13.photobucket.com/user/RustyBeach/media/IMG_20140311_113639.jpg.html" target="_blank">http://i13.photobucket.com/albums/a287/RustyBeach/IMG_20140311_113639.jpg</a> Thanks! I am assuming that you have a thoroughly cleaned chamber. Since you have ruled out ejector/extractor issues, here are the remaining things to check for. Load only one round and test fire, does it lock back on an empty mag? Repeat this test multiple times. Also, manually pull back the BCG with the charging handle and look inside the ejection port. Does the front of the bolt lugs retract past the edge of the port, where it meets the base of the deflector? If so, there is too much rearward travel of the BCG, possibly causing rounds to deflect off the edge of the port and bounce back in. You should see at least 1/8" to 3/16" of the bolt lugs protruding into the port. If both of those tests pass, then suspect that the rifle is overgassed and cycling too quickly. |
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Also, manually pull back the BCG with the charging handle and look inside the ejection port. Does the front of the bolt lugs retract past the edge of the port, where it meets the base of the deflector? If so, there is too much rearward travel of the BCG, possibly causing rounds to deflect off the edge of the port and bounce back in. You should see at least 1/8" to 3/16" of the bolt lugs protruding into the port. Just did this, and the bolt goes rearward past the deflector quite a bit. |
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Just did this, and the bolt goes rearward past the deflector quite a bit. Quoted:
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Also, manually pull back the BCG with the charging handle and look inside the ejection port. Does the front of the bolt lugs retract past the edge of the port, where it meets the base of the deflector? If so, there is too much rearward travel of the BCG, possibly causing rounds to deflect off the edge of the port and bounce back in. You should see at least 1/8" to 3/16" of the bolt lugs protruding into the port. Just did this, and the bolt goes rearward past the deflector quite a bit. How far forward is the extension (buffer) tube screwed in? Can you take a photo of it? It may need one more turn, or may be too long and out of spec, or the buffer itself possibly too short and out of spec. |
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Sorry for crappy cell phone pic. <a href="http://s13.photobucket.com/user/RustyBeach/media/IMG_20140312_224118.jpg.html" target="_blank">http://i13.photobucket.com/albums/a287/RustyBeach/IMG_20140312_224118.jpg</a> Here is a simple way to test, remove the buffer spring and buffer, drop two quarters down the tube to act as spacers, replace the spring/buffer and test fire. |
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The buffer is plastic, or the tube itself? Both should be made from anodized aluminum, with the exception of the bumper on the end of the buffer. The buffer tube is aluminum, but the whole buffer is plastic. The only metal in the buffer is the roll pin holding the plastic buffer/bumper together. |
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The buffer tube is aluminum, but the whole buffer is plastic. The only metal in the buffer is the roll pin holding the plastic buffer/bumper together. Quoted:
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The buffer is plastic, or the tube itself? Both should be made from anodized aluminum, with the exception of the bumper on the end of the buffer. The buffer tube is aluminum, but the whole buffer is plastic. The only metal in the buffer is the roll pin holding the plastic buffer/bumper together. That is most likely the issue. I have never seen a plastic buffer, but nothing surprises me any more. If it is indeed polymer, then repeated impact from the carrier would definitely shorten it, as well as possibly being too light. Could you post a photo of the buffer by itself? ETA: just found out that Colt had used polymer buffers in some pre-ban rifles |
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While I had the spring/buffer out, I decided to measure the spring. It is 10 1/2", so within limits. In the picture, you can even see the seam line from the mold. Still a crappy pic. <a href="http://s13.photobucket.com/user/RustyBeach/media/P3120022.jpg.html" target="_blank">http://i13.photobucket.com/albums/a287/RustyBeach/P3120022.jpg</a> I believe that is going to be the main cause of your issue. I would replace the buffer, but would first weigh the polymer one and determine the difference between it and various available weights. Personally, I would start off by replacing with an H buffer, still checking the position off the bolt lugs in relation to the edge of the ejection port. ETA: the one in the photo even appears to be slightly bent or misshaped. This most likely created some drag in addition to length issues. |
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Even if everything else on your "Frankenbuild" was perfect the original problem indicates that the extractor has a problem. Now it could be that the BCG was going back too fast for its little claw to hold onto the case. So since you are buying stuff GET A NEW EXTRACTOR with your buffer.
It is kinda strange that when I was in the military we did not need little extractor donuts (for the M4A1) but now they are all the rage also. |
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Even if everything else on your "Frankenbuild" was perfect the original problem indicates that the extractor has a problem. Now it could be that the BCG was going back too fast for its little claw to hold onto the case. So since you are buying stuff GET A NEW EXTRACTOR with your buffer. It is kinda strange that when I was in the military we did not need little extractor donuts (for the M4A1) but now they are all the rage also. Quoted:
Even if everything else on your "Frankenbuild" was perfect the original problem indicates that the extractor has a problem. Now it could be that the BCG was going back too fast for its little claw to hold onto the case. So since you are buying stuff GET A NEW EXTRACTOR with your buffer. It is kinda strange that when I was in the military we did not need little extractor donuts (for the M4A1) but now they are all the rage also. He just posted that it ran flawlessly after a new spring, and buffer, which is normally what causes stovepipes. See below: Quoted:
Update: Put a new buffer in it, and still having same issue. Figured I would try a new spring,even though the current one measured within limits. After putting both new spring and buffer in, gun ran flawlessly. Thanks for the help. Which would indicate his extractor is fine! |
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