Complex sentence: All shotgun shells (apart from specialized.22 cartridges which hold a very small amount of shot) are center fire, most are made from plastic, shotgun shells, like all centerfire cartridges, can be reloaded and used again.
Split into simpler sentences: All shotgun shells (apart from specialized.22 cartridges which hold a very small amount of shot) are center fire, most are made from plastic. Shotgun shells, like all centerfire cartridges, can be reloaded and used again.