A magazine is provided for a firearm. The magazine comprises a locking mechanism. The locking mechanism has a user interface adapted to enable a user to select between a locked condition and an unlocked condition. The locking mechanism has a rotor movable between a first rotational position when the locking mechanism is in the locked condition and a second rotational position when the locking mechanism is in the unlocked condition. The magazine comprises an elongated shaft connected to the rotor. The magazine comprises a block element connected to the elongated shaft. The block element is adapted to move between a first position when the locking mechanism is in the locked condition in which at least one of firearm operation and magazine extraction are prevented, and a second position when the locking mechanism is in the unlocked condition in which firearm operation and magazine extraction are enabled.