Abstract: An apparatus and method for locking a gun. The apparatus includes a dummy round configured for insertion into a firing chamber of a gun, a locking component configured for coupling with the dummy round, and an elongated sleeve rotatably coupled with the locking component. The locking component includes a keyed head positioned within a longitudinal channel of the elongated sleeve. The locking component and elongated sleeve are insertable through the discharge end of a gun's barrel. An actuating mechanism, such as a key is insertable through the channel of the elongated sleeve to engage with the keyed head and rotate the locking mechanism relative to the elongated sleeve. Rotation of the locking mechanism effects a friction lock between the locking mechanism and the dummy round.