You transmute as many as three pebbles, which can be no larger than sling bullets, so that they strike with great force when thrown or slung. If hurled, they have a range increment of 20 feet. If slung, treat them as sling bullets (range increment 50 feet). The spell gives them a +1 enhancement bonus on attack and damage rolls. The user of the stones makes a normal ranged attack. Each stone that hits deals 1d6+1 points of damage (including the spell's enhancement bonus), or 2d6+2 points against undead.