An ammunition cartridge has a casing and a bullet. The casing has a tubular body closed at one end and attached at the other end to the bullet. An internal surface of the casing attached to the bullet is provided with a coating of copper oxide. The copper oxide may be black, for example black cupric oxide. The coating can result in a more consistent and reliable separation of the bullet from the coated casing compared to an uncoated casing and this can assist the accuracy of the ammunition.