The 270 Winchester Short Magnum

or 270 WSM is a short, unbelted, magnum cartridge 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 It is a member of the Winchester Short Magnum family of cartridges.

270 Winchester Short Magnum

270 WSM cartridge


Place of origin

Production history





Parent case
.300 WSM

Case type
Rimless, bottleneck

Bullet diameter
.277 in (7.0 mm)

Neck diameter
.3140 in (7.98 mm)

Shoulder diameter
.5381 in (13.67 mm)

Base diameter
.5550 in (14.10 mm)

Rim diameter
.535 in (13.6 mm)

Rim thickness
.054 in (1.4 mm)

Case length
2.100 in (53.3 mm)

Overall length
2.860 in (72.6 mm)

Rifling twist

Primer type
Large rifle magnum

Maximum pressure
65,000 psi (450 MPa)

Ballistic performance

Bullet mass/type

90 gr (6 g) JHP
3,700 ft/s (1,100 m/s)
2,737 ft⋅lbf (3,711 J)

130 gr (8 g) HP
3,295 ft/s (1,004 m/s)
3,135 ft⋅lbf (4,250 J)

140 gr (9 g) SP
3,250 ft/s (990 m/s)
3,284 ft⋅lbf (4,453 J)

150 gr (10 g) SPBT
3,136 ft/s (956 m/s)
3,276 ft⋅lbf (4,442 J)


Following the immediate success of the .300 WSM in 2001, the .270 and 7mm WSM were introduced in 2002. The last of these cartridges, the .325 WSM, was introduced in 2005.270 winchester short magnum

Like its siblings, the .270 WSM has gained a steady following for a variety of reasons. One of the foremost factors in the success of these cartridges has been the reduction in both size and weight of rifles in comparison to traditional magnum chamberings. The .270 WSM has also given fans of the .270 Winchester a cartridge which boasts greatly enhanced performance supported by readily available factory ammunition.270 winchester short magnum

These cartridges have quickly became popular world wide, with a variety of ammunition found in gun stores around the world. The WSM’s have also received a small amount of negative criticism. Poor magazine to chamber feeding and excessive pressures resulting in difficult extraction have been major complaints. Both of these issues have been addressed at a design level. The most recent of complaints has been the cost of ammunition, ever rising due to metal market demands in developing nations.270 winchester short magnum

The .270 WSM is the third in what is now called the trio of .270 (.277”) caliber commercial cartridges. These include the .270 Winchester, .270 WSM and the .270 Weatherby Magnu