Makes it a Level 5 felony for a: (1) licensed importer, licensed manufacturer, licensed dealer, or licensed collector (licensee); or (2) person who is not a licensee (private seller); to knowingly or intentionally sell, trade, give, transport, deliver, or otherwise transfer a firearm to a person whom the licensee or private seller knows is less than 21 years of age. Specifies exceptions that apply to a private seller. Requires a court to impose consecutive sentences upon a private seller who is convicted of certain offenses.