This is a brand new CMT "MP Tested" bolt that I bought with a CMT bolt carrier group.
To the right is a RRA bolt part of a RRA bolt carrier group I bought several years ago. It has about 1000+ rd through it and has run fine thus far. I needed a new BCG for a new AR build.

Notice the excess wear/polishing on the extractor tail. The RRA extractor did NOT have any wear at all until I put the RRA extractor into the CMT bolt and ran it through the CMT bolt carrier manually (notice slight wear at the edge).

I've come to the conclusion that the CMT bolt itself wasn't machined for enough insertion depth of the extractor causing it to stick out higher than the round bearing surface of the bolt. In addition, the CMT extractor is a few thousandths of an inch thicker at the tail end. This extra material coupled with the "improper" depth causes it to stick out and drag against the inside of the bolt carrier. I thought it was tight because of the new gas rings but I found its tight because of this.

Has anyone else seen this before? What did you do besides replace the bolt/extractor?

ETA: Talked to Denny and it's normal wear. 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!

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.

Sounds like a self correcting problem to me.

Quoted: Sounds like a self correcting problem to me.

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.

do you have an insert or some sort of "enhancement" produtct under there?

Quoted: 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.

+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.

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

Quoted: Quoted: Sounds like a self correcting problem to me. 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.

Sorry, mis read your first post. Though the CMT had lots of rounds thru it....

Send it to CMT for a new bolt.

Does anyone have contact info for CMT?

Quoted: Does anyone have contact info for CMT?

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.

Tell 'em to stake their carrier keys better, while you're at it.    

Quoted: Tell 'em to stake their carrier keys better, while you're at it.

I sent them a link to Tweak's thread

ttt bump for night crew

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.

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

Tell me about it, I don't think I'll ever finish this M4 build  

Just the SHOT Show

Quoted: 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

Quoted: Just the SHOT Show Quoted: 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

Didn't the SHOT show end on 12 Feb 2006?

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!

Glad it is not normal on any of mine.

Quoted: Glad it is not normal on any of mine.

+1

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.

Now that's customer service!

Mine has the same wear pattern after 120 rounds. It works fine but now you people have got me worried.

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

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.