Chromatic Bullet

around your firearm, imbuing it with acid,
cold, fire, lightning, poison or thunder energy. This power
surges around the outside of a gun in an effect that is
harmless to you, such as a raging fire or a bubbling film of
acid. This power remains inside your gun for 1 minute after
you cast it unless it is used or another power is put within
your gun, such as Black Bullet. When you succeed an attack
roll with nonmagical ammunition from this gun, the round
instead deals 1d8 damage of the damage type chosen.
This spell's damage increases by 1d8 at 5th level (2d8),
11th level (3d8), and 17th level (4d8).