How many shots does it take from a pistol to braek an iron chestplate?

In minecraft, it takes a total of 19 shots from a pistol (or more specifically, a crossbow) to break an iron chestplate, assuming the shots are not critically hit and the target is not wearing any additional armor or enchantments. However, if the target has protection enchantments or other armor pieces, it may take more shots to break the chestplate.