A simple chamber flag made for the AR-15.
Glue a cut down spent .223 case into the bottom of the chamber flag to make it extract like a real case when pulling the charging handle.
Do not insert when hot!
Hint: From what I know, this is banned at IPSC since it includes an ammuniton part.
Print standing up with a impact resistant material such as PETG or Nylon.
The author hasn't provided the model origin yet.