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Posted: 10/31/2010 7:24:16 PM EDT
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All:
New build, first time out. About 20 rounds downrange and the weapon starts failing to extract. Brass is not hard to tap out to rectify the situation. A few slaps of the hand on a cleaning rod drives them out no problem. Ammo is Nato SS109 (British Aerospace). Start looking at my brass and every round has some deformation in the rim where the extractor is engaging like excessive extraction force is necessary. The ones that are stuck are peeled back but not the entire rim. The rim is peeled in such a way that looking at the casing headstamp reveals no damage. The rim is not "pulled through" by the extractor. Just the corner is peeled off. I tried to take some picture but none are coming out. There are no other problems with the cases other than that deformation from the extractor. So I'm wondering if I have 2 minor problems making a major problem. First problem is overgassing. Bolt is trying to extract spent casing while chamber pressure is still very high. Casing walls are pushed tight up against the chamber walls making force necessary for extraction excessive. Possible problem 2.: poor extractor geometry or spring tension not allowing full engagement of the extractor in the rim once the rim begins to yield. To top it off this is a new, never been fired rifle. The lower is Stag. The rest was assembled from a kit made by a manufacturer who will remain nameless until I give them a chance to make good. If I could fix the problem with an H2 or H3 buffer or stiffer spring and be satisfied with the results I would be happy. If I end up having to chase the problem I's rather let the manufacturer deal with it. My questions to the hive: What do you think of my hypotheses? Am I crazy for even wanting to tackle the problem on my own instead of sending at least the upper back to the manf. being its a new weapon? Thanks. |
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Questions-
Barrel Length? Gas System (carbine, midlength, rifle)? Chromelined chamber and bore? 5.56 or .223 rem chamber? First thing, check that the chamber is clean, and is free of lube, carbon, or other foreign matter. Does your brass show any scratches to lead you to believe there maybe a burr. Now inspect your extractor does it look like it had enough purchase on the rim of the case? Your description sounds like a weak extractor spring. So pick a BCM bolt upgrade or equivelant. Indeed if the problem persists you may have an issue with chamber pressure causing extraction problems. |
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I would also agree with just getting the BCM upgrade kit and trying that first and also clean the chamber real good. The problem will be something with the chamber or bolt(extractor) or ammo.
I dont think gas is going to be the problem here. Make sure everything is cleaned well and oiled well. Including the inside of the buffer tube and buffer. re-oil everything and run it some more. It may need a little more breaking in. but i would still get the BCM upgrade anyway. |
| OK sounds good to go then. The carbine system does have higher chamber pressures upon unlock, thats why the upgraded spring/insert and o-ring came about, if the problem persists after upgrading send me an IM and we'll brain storm some more. A heavier buffer may increase dwell time while the chamber drops in pressure. Have you tried other ammunition, you might have a hot lot of ammo. |
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Thanks for your help gentlemen. FYI I caled the manf. They seem to believe its a bolt issue and are sending me another. I have my doubts but we'll see. Seems to me like it has to be extractor or overgassing or some combination of the two. I may pick up a BCM bolt when I pick up the upgrade kit. I will keep you posted as to the results.
Thanks again. |
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Update:
Replaced the bolt with a BCM and problems disappeared. No damage to casings and brass is ejected at 3 o'clock. Del-Ton is the manufacturer. They sent a replacement bolt, but I was having so much fun with the rifle I forgot to test theirs out. I have no complaints about Del-Ton's service. Once I called them and left a message that I was having a problem they aggressively pursued it. They called me back in about 15 minutes. Once I get a chance to use their bolt I'll report back. They seem very motivated to provide the best product they can. They said they are building up an HP test booth FYI. |
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