The Full Metal Jacket (FMJ) is a type of bullet commonly used by the military. A lead center (core) is surrounded by a strong metal coating (jacket). This jacket is usually made of a copper alloy, but sometimes it is made of steel. The FMJ does not spread out when it hits a target. It goes deep into its target and is a general-purpose bullet. The FMJ is not recommended for hunting. It is mostly for target shooting and military use.