Rust, carbon buildup, or...?

[Skyyr]

I was cleaning my AR today and noticed that the chamber has a browish discoloration everywhere except where the bolt carrier/bolt come into contact with the front of the chamber. It appears to be carbon buildup, but the crap won't come off.

Is this normal? I have a few AR's and this is the only AR that doesn't seem to want to come clean. Is this carbon? Or something else?

http://i.imgur.com/5m4p1LC.jpg

[foxtrotx1]

Brass, and lube discoloration I think.

[1gunzenuf]

I was cleaning my AR today and noticed that the chamber has a browish discoloration everywhere except where the bolt carrier/bolt come into contact with the front of the chamber. It appears to be carbon buildup, but the crap won't come off.

Is this normal? I have a few AR's and this is the only AR that doesn't seem to want to come clean. Is this carbon? Or something else?

http://i.imgur.com/5m4p1LC.jpg


Are all of your rifles lubed with the same oil?
Has this one been fired more or less than the others that cleaned up?
Did this particular rifle sit for a long time without being cycled or fired?
Any steel cased ammo fired through this one?
And most importantly, did you lube with FireClean? - Sorry, just kidding.
Have you attempted to use chemical cleaners or solvents to remove the discoloration (brake or carb cleaner or a good quality solvent or mineral spirits)?

It does not look like any carbon fouling that I am familiar with. It looks like cooked on lube or some of the gunk off of the cheap steel cased ammo (resin of some kind maybe). Please keep us updated as to whether or not you get it to clean up and what, if anything it took to get the job done.

Then again, if it doesn't affect function, then maybe you just need to shoot it more and see if that works.

[556BlackRifle]

Are you using Crisco? ;)


Seriously, I'm not sure what oil you're using but it looks like varnish. Try some #9 or some other good solvent and see if that loosens it up.

[Singlestack Wonder]

A combination of heat mixed with various gun powders and lubes over time. Its not a problem. The chamber is clean, just discolored.

[Skyyr]

Thanks for the replies.


Are you using Crisco? ;)
Seriously, I'm not sure what oil you're using but it looks like varnish. Try some #9 or some other good solvent and see if that loosens it up.

:P

I use Breakfree CLP for cleaning and storage. I use SLiP EWL 2000 for lube.


A combination of heat mixed with various gun powders and lubes over time. Its not a problem. The chamber is clean, just discolored.

Thanks, makes sense. Is there any practical way to remove it? Or is this normal discoloration over time?

[556BlackRifle]

Thanks for the replies.



:P

I use Breakfree CLP for cleaning and storage. I use SLiP EWL 2000 for lube.



Thanks, makes sense. Is there any practical way to remove it? Or is this normal discoloration over time?

Try carburetor cleaner. It should cut through the varnish. Just make sure not to get it on anything else just incase it may damage the finish.

[bfoosh006]

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[RVTMaverick]

Crisco ( Fireclean )...Now that was funny !

If it is varnish various solvents should clean it off. FYI, It is a non-issue one way or another.

How old is the rifle ? It looks a lot like the OEM rust preventative.


LOL This is Exactly what I was thinking it looked like, (rust preventative)....?

[Skyyr]

Crisco ( Fireclean )...Now that was funny !

If it is varnish various solvents should clean it off. FYI, It is a non-issue one way or another.

How old is the rifle ? It looks a lot like the OEM rust preventative.

This particular one is about four years old, but doesn't have a high round count.

[bfoosh006]

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[Dionysusigma]

For what it is, versus the effort to remove it, versus how it will affect function, I'd go with what several have said and agree to not bother with it.

Think of it like exhaust buildup on a car's tailpipe.

[HansTheHobbit]

I assume you're talking about the brown spotting on the lugs and not the bright brass built up in the crevice between the extension and the barrel. Those dark spots looks like rust to me, but it's hard to tell from a photo. Get after it with a little steel wool and some Hoppe's. Just rub it a little bit, then wipe it with a patch. If it's rust colored, then you know.

I had a rust problem like that not too long ago on a pistol barrel. The steel wool took care of most of it. Successive cleanings, along with Mil Comm MC2500, eventually got the rest of it.