.300 Winchester Short Magnum (also known as .300 WSM) is a .30 caliber rebated rim bottlenecked centerfire short magnum cartridge that was introduced in 2001 by Winchester.
.300 Winchester Short Magnum Wikipedia
The cartridge overall length is 72.64 mm, cartridge case is 53.34 mm in length and the bullet diameter is .308 in (7.82 mm), which is common to all U.S. .30 caliber cartridges. The principle at work in the short magnum cartridge is the advantage of fitting larger volumes of powder in closer proximity to the primer's flash hole, resulting in more uniform, consistent ignition.
The advantage to this round is the ballistics are nearly identical to the .300 Winchester Magnum, but in a lighter rifle with a shorter action. A disadvantage of cartridge case designs with relatively large case head diameters lies in relatively high bolt thrust levels exerted on the locking mechanism of the employed firearm. Also in small ring actions the larger chamber diameter removes more steel from the barrel tenon making it weaker in a radial direction .
The .300 WSM is adequate for hunting moose, black bear, brown bear, elk, mule deer, and white-tailed deer in forests and plains where long range, flat shots are necessary. The .300 WSM is also used in benchrest shooting.
The .300 WSM has a standard bullet diameter of .308 or 7.62mm and takes advantage of the numerous bullet options available in that caliber.
The .300 WSM is a Delta L problem cartridge, meaning it can present unexpected chambering and/or feeding problems. The Delta L problem article explains this problem in more detail. The .300 Remington Short Action Ultra Magnum has very similar cartridge dimensions but is not interchangeable.10.69 g (165 gr) Full Metal Jacket(FMJ): 982 m/s (3,223 ft/s)
11.66 g (180 gr) Full Metal Jacket(FMJ): 943 m/s (3,095 ft/s)