the 243 wssm is an addition to the winchester super short magnum (wssm) family of cartridges, which also include the .223 wssm and the .25 wssm, and the idea behind the 243 wssm was to develop a compact, higher velocity version of the well-established and internationally popular .243 winchester unveiled by winchester in 1955. the 243 wssm was first introduced in 2003.