A firearm locking system includes a magazine plug assembly and a locking bracket. The magazine plug assembly has an outer body configured to fit within a magazine well of a firearm and includes a locking mechanism partially contained within the outer body. The locking mechanism includes a locking bar configured to partially extend into a barrel of the firearm when an actuatable end of the locking bar is pivoted from an unlatched position to a latched position. The locking bar is then held in the latched position by a locking bracket that is secured to the base of the magazine plug assembly by inserting the actuatable end of the locking bar into a cooperatively sized slot within the locking bracket and then inserting a padlock shackle into an opening within the actuatable end of the locking bar.