Starting to reload a new caliber. I have 6.5 mm CM and 6mm CM brass. I wish to be able at a glance to ID the brass so I don't get it mixed up while shooting or cleaning. I know i can use vinegar and salt to tarnish it but don't know if tumbling will get rid of the tarnish (I assume so). I wish to blacken it without effecting the brass metal. Any Ideas ?