What is this stain on inside the chamber

[dyi]

This is a never shot Sig m400. Anyone know what is this weird stain on the chamber wall?


https://photos.app.goo.gl/KuUe9fy7tzeRbaFq5

THanks,
Dan

 

[Meroh]

This is a never shot Sig m400. Anyone know what is this weird stain on the chamber wall?


https://photos.app.goo.gl/KuUe9fy7tzeRbaFq5

THanks,
Dan

Chamber, or in your upper? Can you zoom out a bit for perspective?

Thanks,

 

[DavenK]

Thats old dry grease/lubricant, wipe it off...

 

[Blastattack]

This is a never shot Sig m400. Anyone know what is this weird stain on the chamber wall?


https://photos.app.goo.gl/KuUe9fy7tzeRbaFq5

THanks,
Dan

That’s not the chamber at all, that’s just the inside on your receiver. Looks like dried lubricant. Try wiping it out. If that doesn’t work, then shoot it. If you experience no problems, then just stop worrying about inconsequential things.

 

[tigrr]

Could be from the type of heat treating they used.

 

[Matt K]

It is called Dry Film Lubricant and is baked on as a factory process. It is a MilSpec requirement.

 

[sidester]

What does it taste?

 

[dyi]

It is called Dry Film Lubricant and is baked on as a factory process. It is a MilSpec requirement.

Thanks guys for all the help! I tried a bronze brush but it's still not coming off. I guess it's what Matt K said.

 

[Rebel Rouser]