I don't think there are pure copper bb's. BB's generally are copper plated steel. A copper bb would weight less than a steel BB, and therefore have less momentum and penetrating power. T he copper plating eliminates corrosion of the BB and reduces er...
It's not worth the bother. Throw it out and buy a new one (they are quite cheap nowadays).
My kettle is also a breville and originally had the metallic taste you are referring to. I took it back and exchanged it and found the second one to have the same taste. I tried boiling milk and it did dull the taste but remove it altogether. The onl...