Removing carbon from face of barrel extension?

[Skyyr]

I have a new upper (only ~500 rounds through it) and I went to clean it after taking it to the range. I noticed that where the BCG came into contact with it, the face of barrel extension was shiny. All around where it did not contact had a coating of carbon - nothing thick, but enough that it looked parkerized/discolored. I've never had this happen before with so few rounds. I believe this to be carbon - how do I remove it? I tried everything but it's almost like the carbon is just thin enough that it's smooth and scrubbing doesn't do much. I used some KG-1 carbon solvent and it didn't appear to do anything.

Any tips?

http://s9.postimg.org/90p5brthn/photo.jpg (http://postimg.org/image/90p5brthn/)

[Heavy Metal]

Might be assembly grease.

[Grand58742]

Have you tried the chamber stars like these?

http://www.midwayusa.com/product/737572/real-avid-ar15-star-chamber-wool-cleaning-pads-pack-of-20

[Tire]

are you sure it's not just uneven finish on the face of the extension?
24669

[markm]

How do you remove it? CLP and Q tips. Just jam them into the corner where the upper and extension corner out..

[Skyyr]

How do you remove it? CLP and Q tips. Just jam them into the corner where the upper and extension corner out..

I tried that - nothing would come off. See the updated image (above).

Notice that where the carrier contacts the extension, it's shiny/polished. Elsewhere, it's discolored. I've never had this happen before.

[markm]

I'm not seeing enough to worry about. Looks discolored around where the carrier hits, but that's it. ??

[Skyyr]

I'm not seeing enough to worry about. Looks discolored around where the carrier hits, but that's it. ??

It's darker in person (the flash greatly lightened it). I'm not so much concerned with it as I am curious as to why, out of several uppers, this one has staining/carbon buildup? And, secondarily, how to remove it.

[LewP]

Looks like oil or grease that has been vaporized and deposited on the barrel extension. Unless it starts to build up I wouldn't worry about it.

Have you been doing some mag dumps?

[Skyyr]

Looks like oil or grease that has been vaporized and deposited on the barrel extension. Unless it starts to build up I wouldn't worry about it.

Have you been doing some mag dumps?

Nope, not even close. Usually 5-round groups at 200+ yds - a slow rate of fire.

[Wolfpack45]

I wouldn't worry about it, looks like normal wear from the bolt carrier face impacting the barrel extension. If you are concerned about it, maybe try a heavier buffer to slow down the cycle a bit and lessen the impact of the bolt carrier. I use the heaviest buffer that functions 100% in my rifles with the lowest powered ammo I can find. usually that means an H2 or H depending on barrel/gas.

[pohjeekiller]

Have you tried the chamber stars like these?

http://www.midwayusa.com/product/737572/real-avid-ar15-star-chamber-wool-cleaning-pads-pack-of-20

Out f'ing standing. Wish I had these back when I was in. That chamber is a beotch to clean.

-J

[Iraqgunz]

My AR's cry everytime a cleaning thread comes up.

[Intransigent]

Cleaning?

[eodinert]

I like to apply a fresh layer of carbon to protect the carbon deposits below.

[markm]

The cleaner the berry, the sweeter the juice.

[PNorris]

Look up toothette oral swabs. Perfect for cleaning the chamber and extension.

[Straight Shooter]

Get a Dewey chamber rod, and G.I. chamber brush and be done with it already.