Coincidental Combustion is a tier 2 skill in Claptrap's Boomtrap skill tree. When Claptrap shoots an enemy with a non-explosive weapon, it has a chance to deal bonus Explosive damage based on the weapon's damage.

Level 1 2 3 4 5
Explosive Damage Chance +7% +14% +21% +28% +35%


  • The bonus explosive damage is equal to 115% of the weapon's base damage at all ranks.
    • The bonus damage is affected by explosive elemental modifiers, and is not affected by the ACTUAL damage of the initial shot. So, a non-elemental shot against an armored target would deal 80% non-elemental damage from the actual bullet, and the full 115% base damage from Coincidental Combustion. Conversely, against a shielded target, the same weapon would deal 100% non-elemental damage from the bullet, and 92% of the weapon's base damage as explosive damage. This is because the .8x modifier is multiplied against the already-boosted bonus damage, resulting in a net of 92% base damage as explosive against a shielded target.
  • Coincidental Combustion does not deal splash damage, and therefore is not affected by Grenade Damage bonuses.
  • Non-explosive bullets reflected off of Claptrap, such as those affected by the Rubber Ducky action package, have a chance to deal bonus explosive damage as if they were fired by claptrap.
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