Weird discoloration on BCG after shooting suppressed, result of high temps?

[Cunnalinguist]

Hey folks,

I'm a bit of a suppressor newb, perhaps only 500 rounds suppressed fire or so since I picked up my first two cans last October, and am wondering what the discoloration all over my BCG is in these pictures.

This is after about 120 rounds of Tula shot through a Saker 7.62 with a 5.56 endcap on a pinned 14.5 middy, stock gas, with Springco red spring and H buffer. I was shooting a moderate rate of fire. The BCG is a SAA nickel boron unit, and was heavily lubed with FireClean the whole session.

So would the high temps and blow back cause this weird, powdery feeling discoloration? I can't decide if it's from the heat drying out the metal that badly, or is the heat wearing through the nickle boron in parts.

On the inside of the BSG the discoloration seems to leave a powderish residue on my fingers, metallic feeling like. I have also seen this type of discoloration on my brake a day or two after shooting suppressed, even after coating it with FireClean.

Ideas?

[militarymoron]

is this before or after cleaning it? if all that comes off, it's not 'discoloration'.

[MegademiC]

^this, probably burnt lube and powder on the carrier. It will look different on a silver base than black (you'll see the true color more). NIB may turn black over time due to carbon adsorption.

[sc63sallad]

I have the same can and have had the same thing happen on my 300 BLK SBR, which is an AAC and also has a Nib carrier. I was a little worried until I cleaned it and it came right off. I wouldn't worry about it much...

[Shiz]

It's the Tula. once you get it clean, shoot some brass cased through it, it will not stain like that.

[Cunnalinguist]

This is before cleaning. The discoloration cleaned up a bit but not totally.

Thanks for the help, guys. Just wanted to make sure I wasn't baking through the finish somehow.

[Turnkey11]

You're not gonna hurt the nib coating.

[Iraqgunz]

I'm curious as to why Tula would be the cause of this. The carbon appearance is normal for most NiB that I see.

[Cunnalinguist]

I've shot Tula before un-suppressed with this same carrier, and didn't have this happen. This is the first time shooting a can on this rifle.

[AK-47]

There are additives in smokeless powder such as calcium carbonate and nitrocellulose that may be depositing out
Due to increased blowback when shooting suppressed mode. Are you seeing the white deposit in the upper too?
The deposits should clean off.