By adding a charge of black powder to your Bomb, you can change it into a Black Powder Bomb. All of this Bomb's damage dice are d12s. If a target has Resistance to Fire damage, it loses that Resistance for this damage roll. If it has Immunity to Fire damage, it instead has Resistance for this damage roll.
You can use this formula a number of times equal to your Intelligence modifier (minimum of once) and regain all expended uses when you finish a Long Rest.