Short Magnum
Also: WSM · SAUM
A fat, short, beltless high-capacity cartridge designed to deliver magnum performance from a compact short-action rifle.
A short magnum is a cartridge built on a wide, stubby, beltless case that packs magnum-level case capacity into a length short enough for a short action. The Winchester Short Magnum and Remington Short Action Ultra Magnum lines popularized the format in the early 2000s, using a rebated rim so the fat body could still feed from a standard bolt face. The short, fat powder column is often credited with efficient, uniform ignition.
These rounds aim to match or approach the velocity of longer belted magnums in a lighter, handier rifle. The tradeoff is that the large charge behind a given bore can push a cartridge into overbore territory, where added powder yields diminishing velocity, but with faster throat erosion and shorter barrel life.