The Combat Drill weapon in Lancer, located on page 155 of the free version, has an unusual (at least within Lancer's system) damage-determination property that has stymied my attempts to calculate its average damage and heat.
For those unaware, the weapon, when rolling for damage, rerolls 1s as per its Overkill tag, dealing 1 heat (internal damage to a mech) to the user for each reroll. When the Combat Drill hits a target that is Immobilized, Prone, or Stunned and its Overkill tag is triggered (i.e. one of its dice rolls a 1), it deals an additional d6 of bonus damage. Damage dice that have already triggered this property can do so again and dice generated by this property can trigger it, theoretically leading to an exponentially increasing number of d6s of damage.
The drill deals 3d6 Kinetic damage and 1d6 Energy damage by default, but bonus damage is a type of the user's choice from among already-dealt damage. How much damage is dealt on average by the drill when its secondary property is triggered? How much heat does the user take on average when the property is triggered?