it is extremely difficult to win a defamation suit against news media
As a public figure you are absolutely correct. The standard for Libel against a public figure is pretty stringent. Winning as a "private person" is an entirely different standard that is not nearly so stringent.
Assault Weapon is legally defined by the AWB or local statutes.
I think the difficult part is finding a good case. You more or less have to defend a criminal and most of the 2A rights groups try to avoid that.
I thought there were some civil copyright cases being filed without owner permission a while back. I didn't look into it in too much depth, so I may be remembering incorrectly.