Coilgun Balls
Coilgun Balls are an ammo type only used by the Coilgun. It has 3 different versions.
Tungsten
Tungsten is the first useful ball you will be able to use. It destroys blocks infinitely and pierces through the blocks that it can't.
Crafting recipe for Tungsten Balls.
Ferrouranium
Ferrouranium is highly similar to Tungsten. It destroys and pierces block infinitely. The difference between the two is that Ferrouranium balls do more damage than Tungsten.
Rubber
Rubber is most likely the first ball you will ever use. It does significantly less damage and can "bounce".