The more Steam Points that are expended in the Steam Cannon, the greater its maximum range will be. If you choose not to expend any Steam Points in the Steam Cannon, or if the Steam Tank is in base contact with an enemy unit, you cannot fire it that turn.
If you expend a single Steam Point, the Steam Cannon can fire with a maximum range of 12". For each additional Steam Point you expend, the maximum range of the Steam Cannon is increased by 12". The Steam Cannon can only be fired directly ahead.
If the first artillery dice roll is a misfire, the Steam Cannon does not fire and the Steam Tank immediately loses D3 Wounds with no armour saves allowed. The Steam Cannon cannot fire grapeshot.