My EABCO accuracy barrel in 6.5 CM is a copper mine. I get 5 shots in a tight group and then it starts to loosen up. 20 rounds down the barrel, and endoscope reveals a bright copper colored bore. Lots of Gunslick foaming bore cleaner, lots of bright blue colored patches later, and then start all over again. Shoots well when clean, but coppers up real fast.

Hope yours is better.