ok you realize that FMJ bullets are just normal bullets right
like you dont have to specify that a bullet has a full metal jacket, the generic non-hollowpoint non-armorpiercing kind of bullet is characterized by a full metal jacket; ie, it is basically a lump of metal surrounded by another lump of metal for the sake of aerodynamics and smoother internal operations
and beyond that shotguns work by firing lots of little tiny like metal pellets as opposed to a traditional single bullet, and those metal pellets are always just solid metal all the way through because they don't have to be aerodynamic or come into contact with the internals of the gun
like if anything shotgun shells all universally have full plastic jackets