The initial TSA person was flipping out over a piece of expended brass in a tube pocket that I never use. The TSA supervisor who responded thought it was kind of funny, and sent me on my way.
The supervisor, in this case, did the right thing. Expended brass is not prohibited. I've heard of people trying to rationalize it as a gun part, but that's ridiculous. It became an issue at our airport because we had a large hunting tourism industry (people wanted to take an Alaskan Grizzly, or Sitka Black Tail) and people like to keep the shell casing that got their trophy. The common sense people among us, of course, wouldn't bat an eyelash at expended brass, but you get those people who think guns and anything related are the devil and make an issue out of a non-issue.