Winchester Short Magnum, or WSM, refers to a family of rebated bottlenecked centerfire short magnum cartridges developed in the early 2000s by the U.S. Repeating Arms Company, the maker of Winchester rifles and one of the oldest firearms manufacturers in the United States. All of the WSM cartridges are inspired on the .404 Jeffery non-belted magnum cartridge which is shortened to fit a short rifle action (such as a .308 Winchester).[1]
It was developed by Rick Jamison in 1997-1998 as proven in a 2005 lawsuit Jamison vs. Olin Corporation-Winchester division.[2] Jamison was given 7 patents on the cartridge design. U.S. Repeating Arms Company used the same concept and the same base case in creating its even shorter Winchester Super Short Magnum cartridges, three of which were introduced in 2003 and 2004.