270 Winchester Short Magnum
270 WSM cartridge
Type Rifle
Place of origin USA
Production history
Designer Winchester
Designed 2002
Produced 2002
Parent case .300 WSM
Case type Rimless, bottleneck
Bullet diameter .277 in (Bad rounding hereScript error mm)
Neck diameter .3140 in (Bad rounding hereScript error mm)
Shoulder diameter .5381 in (Bad rounding hereScript error mm)
Base diameter .5550 in (Bad rounding hereScript error mm)
Rim diameter .535 in (Bad rounding hereScript error mm)
Rim thickness .054 in (Bad rounding hereScript error mm)
Case length 2.100 in (Bad rounding hereScript error mm)
Overall length 2.860 in (Bad rounding hereScript error mm)
Rifling twist 1-10"
Primer type Large rifle magnum
Maximum pressure 65,000 psi (Bad rounding hereScript error MPa)
Ballistic performance
Bullet weight/type Velocity Energy
90 gr (Bad rounding hereScript error g) JHP3,700 ft/s (Bad rounding hereScript error m/s)2,737 ft·lbf (Bad rounding hereScript error J)
130 gr (Bad rounding hereScript error g) HP3,295 ft/s (Bad rounding hereScript error m/s)3,135 ft·lbf (Bad rounding hereScript error J)
140 gr (Bad rounding hereScript error g) SP3,250 ft/s (Bad rounding hereScript error m/s)3,284 ft·lbf (Bad rounding hereScript error J)
150 gr (Bad rounding hereScript error g) SPBT3,136 ft/s (Bad rounding hereScript error m/s)3,276 ft·lbf (Bad rounding hereScript error J)
Test barrel length: 24"
Source(s): "Shooting Times" [1] / Accurate Powder [2]

The 270 Winchester Short Magnum or 270 WSM is a short, unbelted, magnum Cartridge (firearms) created by necking down the .300 Winchester Short Magnum and fitting it with a .277 caliber bullet. The correct name for the cartridge, as listed by the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI), is 270 WSM, without a decimal point.[3]


When it was introduced, the 300 WSM sported a new case that showed a lot of promise for uses in other calibers. In 2002 Winchester introduced new cartridges in its Winchester Short Magnum family, including the 7 mm WSM and 270 WSM. This new .270 cartridge was the third commercial .270 ever produced, and the first one in 60 years.[1]

The 270 WSM is an improvement over the older 270 Winchester providing higher velocity with bullets of the same weight, and thus a flatter trajectory and more energy. Velocities tend to be about 250 ft/s (Bad rounding hereScript error m/s) faster, in a cartridge that is shorter and can therefore be used in a shorter action for a more compact rifle if desired.

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