28 Nosler after 40 rounds with borescope

[Mram10us]

With the amount of copper you have I would ditch the nylon brushes. Switch to a bronze brunch and boretech products.

Bronze brush with copper removers?

 

[Timeout]

Bronze brush with copper removers?

Yes. You will get a false positive, blue coloration, but many have moved away from the nylon brush in hopes to remove copper. The bronze brush works much better and faster. Contrary to what some believe when used properly it will not harm your barrel. You have a real copper mine there. I hope that once you get it clean it will not appear so rapidly. Sometimes on a new chamber job there is a sharpness where the bullet transitions into the rifling. That leads to tearing of the bullet jacket and depositing copper all through the barrel.

 

[RadioJock]

To get rid of the copper you need to use a bronze brush.
You need a more aggressive copper remover like sweets and a bronze brush. Don't be afraid you won't hurt the barrel.
You need to cut into the copper to start to dissolve it. The solvent need to get under the copper to work it out.
Ask a bench rest shooter how it's done.

 

[Tom Erickson]

 

[Tom Erickson]

Before and after