What other material is used to make bb gun pellets?

BB usually weigh in at 5.1 grain, they are made of steel, or Zink plated steel, or Copper plated steel. Lead is also used but not as common as Steel.

Pellets come in a variety of sizes. Calibers from .177, .20, .22, .25, 9mm, 357, 45 Cal and 50 caliber. Each of the sizes also come in different weights. Pellets are made from Lead, Gamo produces a gold plated pellet, but the core is Lead. Lead is used because it's soft. The soft lead skirt of the pellet catches the grooves in the barrel when fired, this makes the pellet spin as it leaves the barrel. BB don't spin, they tumble, and are not as accurate s pellets.

Predator Pellets use a combination of Metal and lead in some of their pellet designs.

Pellets also come in different shapes. The four basic shapes are Round (Universal) Flat (Wadd cutter for targets) Pointed ( distance and penetration) and Hollow-point (hunting).

A few other composites are used but manufactures don't like to disclose their secret.