Gunpowder

Gunpowder is an often-unpredictable substance. As such, firearms, bombs, and other weapons and items utilizing gunpowder have the potential to deal significant damage. If you roll the highest possible number on an individual damage die (such as a 6 on a d6 or a 12 on a d12) when you attack with this weapon, you can roll that die again and add the result to the total. For example, if your 2d4 roll resulted in a 3 and a 4, you can reroll the 4, adding the result to the current total of 7. When a damage die results in the highest possible number on the die, it is called a “burst.”

If you roll the highest possible number again, you can roll the damage die again and add the result to the total, further increasing the weapon’s damage. Any of the damage dice for this weapon, including extra dice such as from a critical hit or sneak attack, can burst and result in a reroll. For each attack you make with this weapon, you can reroll only a number of burst dice equal to your proficiency bonus, regardless of how many damage dice result in the highest possible number.

For example, a 2nd-level rogue fires a pistol and scores a critical hit with sneak attack. The character rolls 4d6 damage dice that result in a 1, a 3, a 6 and another 6. The character then rerolls each 6, resulting in a 4 and a 6. The character adds those results to the current damage total for a final damage total of 26. Since the character’s proficiency bonus is +2, the character can’t reroll the new 6, ending the gunpowder bursts for that attack. When that character makes another attack with the pistol, this process starts anew.

If a single attack with a weapon or item with this property hits multiple targets, the damage is treated as one attack or effect for the purposes of determining how many times the damage can experience a burst, regardless of how many targets take the damage.