Bill HD.4420 is a proposed legislation in Massachusetts that aims to modernize and reform the states gun laws. The bill is titled "An Act Modernizing Firearm Laws" and is a 140-page proposal that seeks to stem the flow of illegal firearms into the Commonwealth. The bill includes several provisions, such as:

• Creating a database that can track guns used in crimes or taken by law enforcement
• Increasing punishments for not reporting lost or stolen firearms to the police
• Redefining terms related to firearms, including what qualifies as an "assault-style" weapon or a large magazine
• Banning more firearms than any other state in the entire country

The bill has been met with both support and opposition. Supporters of the bill believe that it is a step forward in preventing gun violence and modernizing the states gun laws. Opponents of the bill, including the Gun Owners Action League, a nonprofit gun ownership advocacy group in Massachusetts, argue that the bill violates Second Amendment rights and is too restrictive.

The bill was proposed by Representative Michael S. Day of Stoneham and is currently subject to Joint Rule 12. The bill is being discussed in the House Judiciary Committee and the Committee on Public Safety and Homeland Security. The bill is expected to change significantly if it moves forward, and some lawmakers have expressed the need for a more refined bill to make its way through the legislature.