What you are seeing is normal. It comes from the parts rubbing together when racking the slide or shooting the pistol. Make sure to lube those areas and have fun shooting.
Thank you for contacting HK.
Then I would shoot the heck out of it and enjoy it. BUT keep an eye on it.
Already did; they said it was normal. *shrug*this does look REALLY excessive. Especially with such a low round count. The recoil rod should never peen the barrel lug or any part of the barrel with only 600 rounds. Its very strange. Did you send pics to HK? might want to do that and make sure they see what is happening.