Thread: Chamber ringing

I need help understanding chamber ringing. There is info about it on the net but its all Americans practically writing novels about it on other forums and not using layman's term so I still don't know to look out for. A picture speaks a thousand words. Any help will be appreciated.
I loaded some 303 180gn cast pills with 12gn of AP70N, no filler with excellent results in regards to accuracy, grouping and velocity.