Every game I've played where it is relevant uses the "Assault Rifle" term, and way more young people are familiar with game definitions than anything else. Here is roughly how weapons are defined in games:

Submachine gun - Automatic pistol with large clip.

Rifle - Single shot long barrel higher calibre weapon

Battle Rifle - Burst fire rifle with large clip

Assault Rifle - Automatic fire rifle with large clip

Machine gun - Belt fed automatic fire rifle

Edit: Nothing legal about the above, of course, just noting what the general population would associate with each term. And you can understand why people would be worried about automatic fire high calibre weapons. They aren't useful for anything other than to kill lots of people.