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Posted: 9/1/2010 5:34:09 PM EDT
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Hey, I am trying to help a friend with his department issued oylmpic arms ar15(I know a department issed oly, wtf). I am an ar15 armorer and usaly don't have any trouble fix these problems.
The rifle is a 16in hb oly arms with and a2 upper and a 4 position car stock. It appears to have a standard car buffer. The problem is it fails to eject a fired case and then tries to load a live round from the mag. The live round gets into the chamber but the spent round stove pipes. It happens about 1 out of 20 rounds. I was mostly using p mags. My friend said it happends about every 3-5 rounds. When I shot it it was only once a mag maybe less. I don't think it is short stroking because it locks back on empty mags. When I first picked the rifle up I took it home and looked it over for anything that might be causeing the problem. All gas rings are there and the carrier key is tight and staked. When I shot it I was using www, fed xm193, wolf, monache steel, and monarche brass. It seemed to have the failure with all the ammo except the monarche steel. After I saw it fail a few times I tried replacing the extractor, spring and o ring. When I replaced those I noticed there was no insert in the extracor spring(not sure if that is normal for oly) I did not have an extra to put in so I just tried it with the new etractor and spring. Still fte about the same rate. Do y'all think the lack of the insert might be causing the fte. It appears to extract fine and the ejector seems to operate fine too. I have seen guns with out the insert before that ran fine, so I was not sure if some don't need them(all of my guns have the insert and the o ring. After switching the extractor and spring and still getting the fte about once every mag I started to get low on ammo. I then took out a brand new m16 bolt group I got from bravo co. I tried it but only had 20 rounds left. It ran fine and seemed to eject a little farther, but only putting 20 round through it I'm not sure that fixed it. The bolt was only to track the problem, I using it for one of my guns so even if it is 100% with my bolt I still need to get the other one fixed. Tomorrow I'm going to get some more ammo and see if my bolt is 100% in the oly, I'm also going to pick up an insert to see if that helps. Do y'all have any other ideas? I know the olys are not that great but it should not be failing that offten. Do y'all think adding the insert to the extractor spring will help, maybe an extra power extractor spring? Thanks, james |
| I've got 2 friends that bought that same rifle and had the exact same issues. I thought it was a gas problem and replaced the tubes in both and it seemed to clean it up a bit. I also noticed it seemed to happen more with 5.56 ammo vice .223. Didn't matter the mags, I ran the mags right from both guns when they were having issues and my gun ate it just fine. Both Oly's had the same issues when running my mags. GI mags and P-Mags. I'll have to look at their guns and see if they have an insert in the extractor too. |
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If the bolt is locking back on the last round out of the mag, then the stroke is fine, but the spent case is not clearing the action correctly for some reason.
Start off with pulling the charging handle all the way back to confirm that the face of the bolt is not retracting back past the end of ejection port. The bolt face should stop about 1/4" to 3/8" in front of the back of port. If the bolt does retact back/past the back of ejection port, then the case can be defecting back into the action causing the problem. If your good there, then next it could be that the extractor or spring that is not retaining the spent case all the way back to the end of stroke. Yes, the extractor spring should have an insert since it keeps the spring from collapsing sideways, but further more, the extractor hook should be sharp and the spring with strong tension. If needed for testing, installing a #60 ring around the extractor will give it more tension to confirm that the spent case is not being dropped before end of stroke. Lastly, do not weed out the ejector as being the problem as well. You can hook a spent case off the extractor to test, but you want to make sure that the ejector is gliding cleanly in the bolt face channel, and not binding up. Also, the extractor spring should have a great deal of tension and if you find the ejector spring to be weak, it should be replaced. |
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Somewhat related post.
Extractor assembly failure is more common, but don't forget the ejector (more likely the ejector spring actually). I would detail strip and clean the bolt, paying special attention to the ejector channel. It's possible to get debris packed in there that inhibits the ejector function. Although a PITA, you might look at sending it back to the mfg for replacement or repair. OA claims a lifetime warranty. |
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Quoted:
Ok, I looked at the bolt and it does go go back past the ejection port, but so do all my other ar15s. The buffer is a little shorter, the plastic bummper seems to be smashed a little. I will let y'all know after I try a insert for the extractor. You found your problem, So either the extension tube needs to be addressed (end or tube or stop collar shortened so it can be threaded into the receiver farther, or drop down some spacers/fender washer on the end of the tube behind the end of spring to limit out the bolt face (Buffer-B/C combo) so the Bolt face does not retract back past the end of ejection port (cases being defected off the back edge of port, and bounded back into the action like now). |
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Ok, its seems to be fixed. I took the extractor, ex spring, inseert, and o ring off of my bcm bolt and put it on the oly. Also put in a new buffer, and new gas rings(thanks jerome) gas rings were a little worn. I ran 100 rounds of xm193 and pmc 100% I'm sure I could figure out the exact problem if I did some more part swapping but I was tired of wasting ammo on this gun. I did have a problem with wolf getting stuck in the chamber, but I think it might be a bad box bcause the wolf also got stuck in my 10.5 lmt. The lmt has never had a problem with wolf before so I think it was the ammo. Thanks again for all the help.
James |
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