I noticed this last night while cleaning my carbine, it almost looks like someone used a grinder on the extractor. It still functions but I was wondering if you guys think its worthwhile to replace since it is a critical part.
Specs: BCM midlength, Daniel Defense BCG, 1700 rounds. I didn’t notice it when I last cleaned at 1050 rounds so it must have happened since then. I have shot steel case through this but not in the last 1200 rounds or so, so I don’t think that’s the culprit.
That is odd, and I do wonder how it happened. I would replace it, just to be safe, as it’s a cheap part. That being said, it is probably worth trying to figure out how it happened, so it does not repeat with a new extractor. perhaps there is some type of burr in the barrel extention that caused this.
Probably a burr or something in your barrel extension. I wouldn’t replace that.
I would think that if there was a burr in the barrel extension then the mark would be more longitudinal. I wonder if a piece of gravel or something got in there and wore it down when it unlocked.
The bolt rotates laterally when it locks into the extension. I’d just monitor it and have an extra extractor… which I’d recommend anyway.
Yes but the bolt is already unlocked when it passes the lugs in the barrel extension, so if there was a burr then I think the mark would be longer. The mark is circumfrential like something was grinding during unlocking, not during rearward travel. But I don’t think there is a burr in there because I don’t see the extractor making contact with anything (even with a snap cap inserted), besides…if there was a burr why would it just now start causing problems at 1700 rounds?
My main concern is not how it happened, but whether or not it is a reason to warrant a replacement.
That mark is on the extractor but is there corresponding wear on the bolt where the parts meet?
Not a scratch. That was the first part I looked at after noticing the mark. I could get a picture with the bolt assembled if you want.
Strange, lateral scratches on a part that moves vertically. If I were to guess it would be grinding marks from a rotary tool. Check whatever the mating surface is for defects at the same location.
Looks like it’s just surface wear.
That’s a pretty thick section of the extractor body, I wouldn’t sweat it. Like Mark said, shoot it and watch it. The claw of the extractor or the pin area are more critical.
Clean and inspect your locking lug area. Flush it out with solvent and blow dry prior to inspection. This is why PMCS is so important. You just never know what you may find.
Perhaps a Blob of foreign matter… 
Just shoot it and keep an eye on it.
Like Quib wrote “Looks like it’s just surface wear.”
It looks as if there was a high spot that made contact and wore the finish off. The striations could be tool marks under the finish. The only way to find out is to purposely remove more of the finish and see if there are tool marks beneath it. As to why it did not show up sooner, an out of spec cartridge case head or some debris under the extractor may have caused it to pivot “open” more than it normally does and the high spot on the extractor rubbed on a lug in the extension.
Also like Quib wrote, it is not a critical area and I would not worry about it.