blue gunk?

[stag88]

Hey guys I just noticed some blue gunk looking stuff at the end of the gas tube. Upper has about 1100 rounds through it, any ideas on what it is?

[Cincinnatus]

Hey guys I just noticed some blue gunk looking stuff at the end of the gas tube. Upper has about 1100 rounds through it, any ideas on what it is?

Have you cleaned and lubed this upper before? What make/model is it?
Does this look baked on or is it viscous? If the former, it's normal, if the latter, could be some funk from what it was lubed with. Mil-comm perhaps?

[stag88]

It's a bcm upper and bcg. And Yup cleaned and lube every range trip.ill lube it and see if it helps, thanks for the input

[Heavy Metal]

Sounds like Cupric Oxide to me.

[stag88]

And what's cupric oxide? Lol

[txpatriot]

oxidized copper fromm your rounds.it is normal

[5pins]

It's from the brass from the bullet jacket reacting with the cleaning solvents. No big deal, just clean it off.

[Redline]

Read this. I had the same problem but I think mine was more green than blue. But I have noticed blue in the past when I use copper remover solvent. Look at Quib's replies. I did what he said with the BF Powderblast and that stuff came right out: "Hit the gas tube with a few shots of BF Powderblast or carb cleaner." Quib is the guy that has the AR cleaning sticky. Good stuff.

https://www.m4carbine.net/showthread.php?t=44610

[Dirtyboy333]

I have the same "gunk" in my 556 and it was from the mil comm TW25B I use. I made the mistake of lightly lubing the inside of the gas regulator valve and after shooting i noticed the valve and piston were "locked" up with each other.

After beating them apart the culprit was carbonized (?) TW25B that had hardened to a bluish green.