A weapon assembly includes a weapon (1) having a weapon barrel (2) which has a barrel bore axis (A), and has a trigger device (3), in which case an aiming device can be attached to the weapon (1) via a weapon-side attachment device (4, 7). A microcontroller (10) is provided, in which a deviation in the alignment of the barrel bore axis (A) of the weapon (1) with the weapon-side attachment device can be stored and can be read by an aiming device. The invention furthermore relates to a method for a weapon assembly, a weapon system and a method for a weapon system. The invention makes it possible to change fire control systems quickly from one weapon assembly to the other.