Minecraft wiki entry for Copper_Ingot, associated text: When killed by a player or a tamed wolf, a drowned has a 11% (11⁄100) chance of dropping a copper ingot. With the Looting enchantment, the chance can be increased to 13% (13⁄100) with Looting I, 15% (3⁄20) with Looting II, and 17% (17⁄100) with Looting III.