Had lots of blue patches out of my 6.5 cm for the 1st 30 rounds had me a little worried. Took it back out yesterday put 50 down the tube the barrel had a little carbon but not even a hint of copper in it not 1 blue patch!!! Best part its shooting in the .2s off a bipod with very little load development!!! I couldnt be happier!!! A big thanks to Jim @ northland great products great service!