Winchester Short Magnum

Winchester Short Magnum, or WSM, refers to a family of rebated rim 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 based on the .404 Jeffery non-belted magnum cartridge which is shortened to fit a short rifle action (such as a .308 Winchester).

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.

The WSM family was inspired partially by a family of proprietary short magnum cartridges developed in late 1997, by John Lazzeroni, derived from a previous line of magnum cartridges he had created. The first Lazzeroni short magnum, the 7.82 Lazzeroni Patriot, was designed to operate in a short-action rifle, instead of requiring a long action. The U.S. Repeating Arms Company was the first major manufacturer to commercialize Lazzeroni's concept, followed shortly thereafter by Remington with their "Short Action Ultra Mag" line.

Another influence was a series of 6 mm cartridges developed for bench-rest target shooting competitions in the 1970s. The idea behind these cartridges was that a short, fat cartridge would be more "efficient" than the traditional long, narrow cartridge, as more of the powder column would be in the immediate vicinity of the primer as it detonated. In turn, this would mean that a cartridge of this type would be able to propel a bullet at speeds comparable to those of "magnum" cartridges of the same caliber using significantly less powder.

The dimensions of the basic case are:

The WSM family of cartridges are Delta L problem cartridges, meaning they can present unexpected chambering and/or feeding problems. The Delta L problem article explains this problem in more detail.

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