Bluish-green patina on suppressor/mount

[elephant]

What is it? What is it caused from?

I have never encountered this before, but on my KAC CQB 556/MAMS set up, I have discovered a bluish green patina in and around the suppressor mount as well as in the suppressor. This was my first time to shoot this gun and I fired 30 rounds last weekend and after shooting, I thoroughly cleaned with CLP and used wire/nylon brush. The gun has been in an unzipped rifle bag in my home until I took it out today.

I have a SilencerCo Saker 556 with an AAC 51T mount and have fired many rounds through it and never encountered this before.
-Thanks

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[dtschirh]

Looks like copper oxide. I bet Hoppes copper solvent would remove it.

[blade_68]

Not much help but I've had that quite a few times depending on ammo I shoot. Most of time it's after shooting steel case ammo ie: Russia stuff. A mix of copper and burnt primer/ powder mixture. On one flash hider it build up to point I chipped off with a brass hammer.... A lot of rounds fired.

[MegademiC]

Verdigris

[georgeib]

Have you used Hoppes #9 on the gun at any point?

[Failure2Stop]

That's vaporized copper adhering to the muzzle device.
Comes off with some KG1 or other carbon/copper removed and a brush.

[pgh_builder]

Copper residue as others have already said. Should come off with some cleaner and a little elbow grease.

[RHINOWSO]

It helps in tightening your suppressor on the mount, over time... with enough build up...

[Giggles]

I've seen that build up on muzzle devices that were not suppressed. It's not uncommon.

[morpheus562]

Is there any harm in not removing it? I have it on both suppressed and non suppressed guns but never thought anything of it.