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Posted: 8/17/2004 12:06:13 PM EDT
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Guru Tweak Hopefully you can point me in the right direction to solve this problem. I will try to describe the problem as I see it and try to give as much of the specifics as I can as per the posting instructions. I am shooting a DPMS 16" BARREL. I use British magazines and the plastic 45 round magazines. Somewhere between 200 and 300 rounds this little rascal turns into a single shot. What happens is that the shell fails to extract after discharge. I have had this problem with wolf, S&B, SA and red box American Eagle. I have tried going up in what I consider ammo quality to see if dirty ammo was the culprit. I took this back to the dealer I purchased it from and he replaced the barrel. I have taken this rifle as my example and working model to an Ar15 armorers class where it was completely stripped and cleaned. At the class the armorer instructor suggested that I try a different bolt (hence a different extractor), which I have done. New extractor, new bolt same problem. I have examined the brass knocked out by a brass rod and I can find no flaw or fault with them. The heads of the brass don't appear to be damage or ripped. Once the gun cools off say an hour or two, it is good to go for 200 to 300 rounds. Your thoughts? Thanks |
Are you saying that the fired case is stuck in the chamber and you have to drift it out with a rod? That usually means a fouled or scored chamber. The incorrect surface finish does not completely release the brass If the extractor groove is not upset then the extractor is not doing its job. There should be some minor dent in any case short of there being no extractor. If the rifle fails to extract only when hot then most likely the chamber is incorrectly cut; too small, out of round, non concentric. |
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I had not shot any wolf through it since the barrel was changed out by the local dealer I purchased it from. That is why I didn't think there was a lacquer build up. The cases have to be drifted out. It usually takes a brass rod and a brass hammer to punch them out and they have some extractor marks on them but nothing serious. I will look there again. My next task will be to insure that the chamber is smooth and polished. More when the tasks are completed. Thanks Jmac |
| i have had the same problem with my m4 upper except it doesn't even take 200 rounds. I haven't shot it enough to really narrow down the problem but i'm sure its the chamber. My question about mine is i'm not sure if it is chrome lined or not and thus might need to be polished a little. |
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m4tactical, Chrome lining is easy to see from the rear of the barrel. Scrub the chamber well then degrease and dry it. You should see shiny metal flashing around the mouth of the chamber. A dab of cold blue can be applied as a double check. Chrome won't blue. You can fabricate a chamber reflector (great use for old firing pins) and check the chamber walls for scoring. Has the headspace been checked?
Check the brass for any rings where the brass flowed into the grooves in the chamber. |
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