Disassembly devices for use with firearms and firearms including such disassembly devices are disclosed. An example firearm includes a frame; a breech slide to be coupled to the frame; a barrel; a trigger bar disposed within the frame; and an arm to be pivotable about an axis between a locked position and a unlocked position, the arm being movable to the unlocked position from the locked position based on a magazine engaging an end of the arm, the arm being movable to the locked position from the unlocked position based on the magazine being spaced from the end of the arm or the magazine not being fully received within the firearm, in the locked position, the arm to interact with the trigger bar to secure the trigger bar, in the unlocked position, the lug to be spaced from the trigger bar to enable the trigger bar to move.