What's this on my IUR?

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Grapeshot

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Picked up an NIB IUR recently, and it had some weird discolouration on the receiver around the chamber area. Asked the seller, who actually had several of them stocked up, and his are the same. Anybody know what this is?

**Edit/TL;DR: It turned out to be a dry film lube applied by CC. Nothing to worry about.**

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Hasn't been fired by me, and those are three different uppers. Looks like some kind of coating or sealant that has been applied to the area, but I can't find any info about it.
 
Graphite or anti-seize lube or something from the barrel install?

A lot of companies use some sort of dry spray-on lube for packing, does it come off with some CLP or gun cleaner?
 
Almost looks like the area was not anodized. The shape looks like oil or something was present and blocked the anodizing process. I wonder if maybe CC keeps the area that the barrel seats into bare for some reason?
 
2 things

it could be
left over residue from anodizing if so wipe with oil and it will go away.
dry film lube that did not take ( if colt still does this to the inside of the upper)
or lastly defective anodizine.
bbb
 
Mine will be here tomorrow, Ill check to see if it looks like yours.

They are Danish Military contract overruns, As long as its effective to put bad guys 6 ft under, The finish isnt a priority...
 
http://www.m4carbine.net/showthread.php?55930-BCM-Stuff

Scroll to post 3, and they seem to describe what's in the IUR pretty accurately. Milky coating that looks sprayed on. Doesn't come off with CLP. Ran some Qtips over the more heavily sprayed areas and there is definitely some extra lubricity or smoothness there.

Dry Film Lube
One of the most common questions/concerns/complaints we get on the BCM upper receiver is the interior finish. Some folks think its unfinished anodizing, or worn finish, or some type of problem. What you are seeing is a dry film lube and it’s a good thing. Many commercial upper receivers may skip that step as it is a cost savings, and most folks would not notice the difference. But Uncle Sam wants it on there, and so does BCM. The dry film lube is a grayish milky type finish. It is sprayed on the interior after the hard coat anodizing is applied. It is then baked into the receiver for about 45 minutes at 250 degrees. The dry film lube is just what it sounds like. It adds lubricity to the interior of the receiver where the bolt group and charging handle travel. It’s a good thing.
Click to expand...
 
I just looked inside my new to me SA20, and it seems to have that coating as well. The coating on the IUR just seems to be much more liberally applied.
 
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