I don't know if you need to define what a firearm is! I think we need to define what a criminal is! Because, according to the 2nd Amendment, the criminal is the one trying to regulate the firearm! Shall not be infringed says it all! But, the criminals are not abiding by this law! Kinda of simple to me! If Its defined as a Firearm! Then it's not possible to regulate it without committing a criminal act! https://youtu.be/i7Wh6aVjt80