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I have had this happen to one of mine. Once the inside of the bolt carrier got dry and carbonized after 700 or so rounds, it caused failures to go completely into battery. It will not be a problem at a low round count but will cause trouble when the weapon becomes dry and heavily fouled. It was a brand new colt bolt BTW.
The ass end of the extractor is too high and is rubbing on the inside of the BC. Remove the cam pin and firing pin, fully insert the bolt and spin the bolt around inside the bolt carrier and feel it bind and momentairly free itself when the high spot rotates into the cam slot. To fix: 1) Strip the extractor from the bolt. 2) Stone down the shiny part on a coarse sharpening stone. 3) Put the extractor back on the bolt, put the bolt fully in the bolt carrier without the cam pin or firing pin. 4) Spin the bolt around inside the bolt carrier and feel it bind and momentairly free itself when the high spot rotates into the cam slot each revolution. You want it to spin totally freely. 5) If it still binds, rinse, lather, repeat. 6) When finished, make sure you get all of the grit from the stone out of everything before final reassembly and relubing. It may help to remove the extractor spring when stoning. Be carefull not to loose it or the insert. Snap it back in by compressing it between the extractor and a hard surface. Big end goes in the extractor. |
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I had a few cast extractors that did that. I swapped them out for the milled ones and it quit. They were angled to high at the rear because of the pin hole location. The cast ones I have show no milling marks on the flats inside or at the two grooves on the sides of the raised portion at the outside end. Some have a small round dot inside near the raised pin hole portion on the inside. Most of the cast ones I have are very hard to get the extractor spring to seat in also.
I would guess it may be the pin hole location on the bolt or extractor or the depth of the front cutout in the bolt that could cause it to happen. |
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Should not matter Stick, the range of travel is limited by the pin and the front of the cut out. The ass end of the extractor should not be able to physically contact the ID of the carrier.
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Did not on mine, I had to correct it. |
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I checked mine and the end of the extractor is flush with the body of the bolt. Bad batch of extractors maybe?
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It REALLY drags against the bolt carrier even when fully lubed. My RRA BCG does not do this and I deem that as ""normal" behavior. HeavyMetal: I'm not sure if its an issue with all CMT bolts or if its just a fluke in this particular extractor/bolt. I measured the depth inside the bolt (where the spring is seated) and the CMT bolt is definitely "shallower". THe extractor is only slightly thicker than the RRA extractor. The bulk of the problem lies with the bolt itself, but using a RRA extractor with the CMT bolt resulted in the slight wear you see in the RRA example shown in the photo. |
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Switching extractors on mine fixed it, still, I fixed the original extractor and it works fine now.
I would see if CMT would adress this as it appears to be a machining issue with the bolt. |
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do you have an insert or some sort of "enhancement" produtct under there?
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Again, what is under will make no difference, its range of motion is checked by the front of the cut out in the bolt unless you are arguing the extractor itself has flex like a spring.
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+1 I do not use the inserts nor do I use an O-ring. Both extractors have the Wolff springs properly installed. The CMT extractor came with a 4-coil spring similar to the Wolff but it appears to be the "HD" spring that is part of the M4 upgrade kit. My RRA came with a smaller coil spring (has only 3 coils). Regardless, it does not matter what I have under there. It's the fact the bolt itself was not machined properly (depth is too shallow for the extractor) and the extractor is a bit thick. |
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I've seen this before. Any guesswhich manufacturer?
Colt, in one of those M16 BCGs from those NIW Colt M16 upper that got out a while back. It had all sorts of stuff wrong with it. Everybody says Colt is the best, and they say that the M16's had a bad rap in Vietnam was undeserved. If all of Colts M16 they send out were as bad as this one, I'd have rather had a baseball bat, because it would have been a more durable club. Extractor was rubbing just like the guy that started this thread. I put in a new extractor with military markings and it worked fine. The Colt extractor was way over dim in the ext pin hole. It was really sloppy loose. It had the weak extractor spring, of course, this is to be expected because they decreased the extractor spring tension so that they wouldn't rip extractor rims off. Put a RRA HB extractor spring it, works great. the gas rings were really tight. I replaced them with RRA gapless rings and the thing slide back and forth like it was half worn out. Cam pin was of the older type heat treat/coating and had worn a considerable groove in it after about 200 rounds in a carbine. Replaced it with a new one and it works great. Here is the thing that was the bastard to track down. The gas key is made out of two passage ways that are supposed to come together in the middle. They didn't, so there was a reduced diameter gas passage. The damn thing drove me batty. I knew it was a problem with the bolt carrier group, because I had shot the barrel before with a different carrier and it had ran fine. With this carrier group, it had a powering problem. It would work for about 8-10 rounds with XM193, but wouldn't go 2-4 shots with wolf. I thought maybe there was a burr or something that would break in but it never did. I replaced the key with a new one and it works great. Thats my story about how I bought a Pony bolt carrier and had to rebuild the whole thing. If a person is around this AR15 long enough, you get to see it from all sides. Brett |
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Sorry, mis read your first post. Though the CMT had lots of rounds thru it.... Send it to CMT for a new bolt. |
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www.stagarms.com Their contact info is there. I am dealing with Mark and/or Jesse on an issue currently. They are responsive to issues with their stuff. |
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Tell 'em to stake their carrier keys better, while you're at it.
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I sent them a link to Tweak's thread |
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Is there a big gunshow/vendor convention somewhere? I haven't gotten any replies back yet. I'm sure Denny or Stag Arms is looking into the issue though
I am not confident in using this bolt + extractor in the rifle. I would not be confident in grinding the extractor just to make it fit, when the real problem is with the bolt. |
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It's not been your month has it . It just goes to show you, it's always something.
One bright thing, your attention to detail is commendable. Mr. Magic would be proud. rj |
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Tell me about it, I don't think I'll ever finish this M4 build
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Just the SHOT Show
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Didn't the SHOT show end on 12 Feb 2006? |
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UPDATE: Talked to Denny and it's normal. He has a bunch of Colt M16 bolts that exhibit the same thing. The chrome lining in the bolt carrier is much harder than the extractor steel. I'm going to slap it into my M4gery build and rock on!
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I am just hoping the $10 extractor doesn't wear out the $70+ bolt carrier. I may try stoning the extractor or just buy a RRA.
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Just call me tomorrow and I will send you another bolt, complete. No problem :) Denny 816 809 9452 |
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Mine has the same wear pattern after 120 rounds. It works fine but now you people have got me worried.
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That's just what some of these threads do. Get people worried over nothing Denny |
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Dont worry about it. I have one the same way and its 20 yrs. old, and all original parts.. Never had any problems with it. I am still using it.
GMan |
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If the inside of the BC gets dry, the friction coupled with the extractor dragging inside the carrier is going to cause problems when using underpowered ammo like Wolf. It just so happens I use only Wolf ammo through the ARs.
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Actually, I had problems with Lake City at a carbine class.
Mine was definately the extractor and not the bolt. Switching extractors fixed it. Arkansas stoning the high spot on the extractor fixed it too. I then replaced the spare with the original extractor. Plenty o' meat there to stone on without hurting anything. |
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