Magic Rocket Ammo (3.5e Equipment)
From D&D Wiki
Rockets are made for use in the Rocket Launcher. They appear as small missiles and are loaded into the back of the rocket launcher. They are created using magic enchantments on shells using the Fireball spell. Rarely (at DM's digression) you may find versions which explode in a blast of lightning, or cold, or acid, or sonic. They cannot be activated just by throwing them, they must be fired out by its launcher.
The default DC is (10 + 1/every 200 over base price). The base price is 200 for one rocket. So a DC 18 rocket costs 1800. The least a rocket can cost is 400 (DC 11).
Moderate evocation; CL 10th; Craft Wondrous Item, fireball.