Fusil of Conflagration

In your shooting phase, you can pick 1 enemy unit within 12" of the bearer and visible to them and roll a dice. On a 1 this artefact cannot be used again for the rest of the battle. On a 2-3 nothing happens. On a 4-5 that enemy unit suffers D3 mortal wounds. On a 6 that enemy unit suffers D6 mortal wounds.