Steel BBs are typically slightly smaller than lead BBs at 0.175-inch (4.4 mm) diameter, although the bore diameter of the barrel are the same.

Some air guns are designed to accept .177 pellets, .177 lead shot, or .175 steel BBs interchangeably.

This is an important consideration in locations where air guns are legally restricted by muzzle energy.

However, because the lighter projectile has a lower ballistic coefficient, it loses its initial energy to air resistance faster than a heavier, slower pellet.

Therefore, a heavier pellet (typically of a larger caliber) may be preferred for hunting.