The ammo used by the A-10 chain gun uses a depleted uranium core that is designed to defeat Chobam and other types of reactive armor. It is also used in F-14, F-15, F-16, and F-18's that are tasked with ground attack missions where active armor tanks are expected to be encountered.

A clarification. The A-10 is equipped with a 30mm weapon, the fighters are equipped with 20 mm. Its the size (30mm) along with the density (depleted uranium) that makes the kinetic weapon so effective against armored targets.