I have used many bore brushes in the past 30 years and from my experience the bronze bore brushes are the only ones to use. The nylon bore brushes do not work well at all. They fail to remove even carbon fouling let alone lead or copper. Stainless steel bore brushes may be OK but I just don’t like the fact that these are STEEL which is the same material the gun barrel is made from. I don’t know if a stainless steel bore brush can scratch the inside of a gun barrel??? I would rather stick with bronze since I know they work really well and will not scratch or damage a gun barrel. Bronze is softer than steel.