Delete

[P11]

delete

 

[Blastattack]

Not rust, just colorful oxidization.

 

[polkey]

Looks like dried oil or remnants of heat treatment. Stainless barrel?

 

[P11]

carbon fiber wrapped barrel. i think its dried oil.

 

[Magellann]

It looks like dried oil to me too, see if it comes off with a toothbrush and some varsol.

 

[Nbhunt3r]

carbon fiber wrapped barrel. i think its dried oil.

You try cleaning??

 

[P11]

M

You try cleaning??

Yah, g36 and some qtips and a rag. Didnt remove much. Gonna try varsol or brake cleaner next.

 

[toxic]

I vote you're combusting some kind of lubricant. ARs like to run wet but I always avoid oil on the bolt piece with the lugs (not sure what that piece is actually called).

 

[Yycbulletsandbrass]

If the gun runs, stop worrying about it.

 

[Pete001]

It's not rust. Don't sweat it and just enjoy shooting it!

 

[silverfoxdj]

Not rust, just colorful oxidization.

That or some lub residue

 

[Dietz]

Looks like cooked up oil to me.

I vote you're combusting some kind of lubricant. ARs like to run wet but I always avoid oil on the bolt piece with the lugs (not sure what that piece is actually called).

Dude, that's pretty much the last place you should avoid to oil...

It's called the barrel extension.

 

[Cpt.Flan]

Barrel extensions are most of the time made of stainless steel... No rust there.

Did the previous owner shot a lot of laquered ammo in this gun?

 

[Chatrbaz84]

another + vote for not rust

 

[NeonGreen]

dried oil by the looks of it