Copper on Barrel Extension?

[tehpwnag3]

I have it on good authority that complete uppers are headspaced and test fired, and it is highly unlikely that a complete lower bought separately would be the root cause of that smudge. I know the OP says it's copper, but to me, that looks like brass from the shoulder of the case. The opposite side looks to have similar marks as well, but not 100% sure from the photo.

[MSplumber]

I have it on good authority that complete uppers are headspaced and test fired, and it is highly unlikely that a complete lower bought separately would be the root cause of that smudge. I know the OP says it's copper, but to me, that looks like brass from the shoulder of the case. The opposite side looks to have similar marks as well, but not 100% sure from the photo.

I see what you're talking about in the picture. I took the BCG out again to inspect, but nothing's in that spot on the opposite side. Must just be the lighting.

Maybe it is brass and it just looks like copper for some reason.

I also notice a little bit of wear in the upper receiver on the right side near the gas tube. I can't get a picture that shows it well, but looks a little too far forward to be caused by the gas key. I found a picture of someone else experiencing similar wear in their AR. Mine's isn't nearly this worn, but it's in the same spot (this is not my gun, just one that shows wear in the same spot): https://i.imgur.com/0LOQiss.jpg

Oddly enough, I checked one of my other ARs and it has the same wear marks there.

[tehpwnag3]

Most likely caused by the charging handle. All good. Thanks for the follow-up.

I see what you're talking about in the picture. I took the BCG out again to inspect, but nothing's in that spot on the opposite side. Must just be the lighting.

Maybe it is brass and it just looks like copper for some reason.

I also notice a little bit of wear in the upper receiver on the right side near the gas tube. I can't get a picture that shows it well, but looks a little too far forward to be caused by the gas key. I found a picture of someone else experiencing similar wear in their AR. Mine's isn't nearly this worn, but it's in the same spot (this is not my gun, just one that shows wear in the same spot): https://i.imgur.com/0LOQiss.jpg

Oddly enough, I checked one of my other ARs and it has the same wear marks there.

[Dr. Bullseye]

I had similar brass particles and asked about it. People said it was nothing and eventually it all went away and I was fine.

[MSplumber]

Just an update: I’ve managed to get pretty much all of the smudge gone with the chamber brush. I’ll just shoot it more and see if it happens again. Either way if it doesn’t malfunction it shouldn’t be a problem, right?

If it was copper, could it have happened when ejecting a live round? When I first started with it, I shot 5 rounds and ejected the last one to go cold.

I want to be sure it’s not even possibly an issue because I love this rifle. BCM makes an excellent carbine.

[Josefius]

I don’t see a problem.


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[tehpwnag3]

Correct. If it starts to malf, report back.

Either way if it doesn’t malfunction it shouldn’t be a problem, right?

[MSplumber]

I was able to replicate a mark in the same spot by ejecting a live round slowly. Observing it during the process, I can see the tip of the bullet rubbing up against that spot. When I let the bolt fly home before it ejects/extracts, it still rechambers just fine. Anyone else have this happen to confirm that it's normal?

copper2.jpg

[AKDoug]

I was able to replicate a mark in the same spot by ejecting a live round slowly. Observing it during the process, I can see the tip of the bullet rubbing up against that spot. When I let the bolt fly home before it ejects/extracts, it still rechambers just fine. Anyone else have this happen to confirm that it's normal?

copper2.jpg

It is fine. You are overthinking this completely. There is a lot going on in there that you can't see when you are firing the gun, if you worried about every little bit of it you'd never get time to shoot. An empty casing will rock up and out to the right when ejected after firing.