Copper on Barrel Extension?

[MSplumber]

I shot 200 rounds through a new rifle yesterday. As I was cleaning it, I noticed what appears to be a copper mark on the barrel extension/chamber face/whatever you call it. I apologize for the poor picture, but if you expand it it should be visible. I can't think of why that would be there, but I can't get it off. I can't imagine that the tip of a round hit it or something without causing a malfunction, and there were no stoppages when I shot it. The picture isn't oriented well. The mark is to the right of the feed ramps rather than up top like it appears.

Any ideas, and is this indicativecopper.jpg of a problem?

[TomMcC]

Brass cases shed bits of brass here and there when feeding, firing, and ejecting. A piece might have got caught between the bolt and breach face, then smeared when the bolt locked. But who knows for sure. It looks like a non-issue.

[MSplumber]

Brass cases shed bits of brass here and there when feeding, firing, and ejecting. A piece might have got caught between the bolt and breach face, then smeared when the bolt locked. But who knows for sure. It looks like a non-issue.

The color makes it look more like copper than brass. I know it's hard to tell by the picture.

[TomMcC]

Well ask yourself...what in your bcg/barrel extension/upper receiver is made out of copper...anything? Is your lube that color?

[MSplumber]

Well ask yourself...what in your bcg/barrel extension/upper receiver is made out of copper...anything? Is your lube that color?

Nah, I use G96 CLP. The only thing I know for sure that's copper in there is when the bullet is fed. It's a BCM, if it matters. I bought the upper and lower separately.

I gotta think it was a bullet hitting right there during feeding. The angle looks about right, but would it have even fed if that happened?

[markm]

If the gun didn't have a functional issue... it's NOT a problem. There's crap flying around all over in that area.

[TomMcC]

Nah, I use G96 CLP. The only thing I know for sure that's copper in there is when the bullet is fed. It's a BCM, if it matters. I bought the upper and lower separately.

I gotta think it was a bullet hitting right there during feeding. The angle looks about right, but would it have even fed if that happened?

If a bullet point made that upon feeding you would have gotten a pretty gnarly malfunction.

[MSplumber]

Maybe it's from hitting the feedramp, but some of the scraped copper got mashed up against the bolt face like you said earlier with brass. I guess it's not a big deal, I've just never seen that before and this is the first AR I haven't bought as a complete rifle so I'm wary about tolerance stacking. It was bought as a complete upper and a complete lower, though. Both BCM.

[TomMcC]

As long as the guns working it's not a prob.

[26 Inf]

Maybe it's from hitting the feedramp, but some of the scraped copper got mashed up against the bolt face like you said earlier with brass. I guess it's not a big deal, I've just never seen that before and this is the first AR I haven't bought as a complete rifle so I'm wary about tolerance stacking. It was bought as a complete upper and a complete lower, though. Both BCM.

You wouldn't have posted the picture and asked the question if you weren't concerned.

Just to allay your concerns, if you bought the upper as a complete unit from BCM (used the add BCG option) just call BCM and ask if they check headspace before they ship the uppers.

If they didn't and you are still concerned, find a local gun shop/armorer to do it for you.

I'm with the others, though, in the opinion you needn't be concerned.