7 mm WSM

7 mm Winchester Short Magnum
WSM and WSSM family of cartridges. From left to right: .223 WSSM, .243 WSSM, .25 WSSM, .270 WSM, 7 mm WSM, .300 WSM, .325 WSM.
Type	Rifle
Place of origin	United States
Production history
Designer	Winchester
Designed	2001
Specifications
Parent case	.404 Jeffery
Case type	rebated rim, bottleneck
Bullet diameter	0.284 in (7.2 mm)
Neck diameter	0.321 in (8.2 mm)
Shoulder diameter	0.538 in (13.7 mm)
Base diameter	0.555 in (14.1 mm)
Rim diameter	0.535 in (13.6 mm)
Case length	2.100 in (53.3 mm)
Rifling twist	1 turn in 9.5"
Primer type	large rifle magnum
Ballistic performance
Bullet mass/type Velocity Energy 160 gr (10 g) 3,050 ft/s (930 m/s) 3,304 ft·lbf (4,480 J)
Source(s): Winchester

The 7mm Winchester Short Magnum (also known as the 7mm WSM) is a centrefire cartridge developed in partnership with Browning Arms Company and Winchester ammunition, making its debut and introduced to the shooting public in 2001.

The 7mm WSM is similar to the .300 WSM and .270 WSM cases necked down to handle .284" bullets. However, the distance from the casehead to the datum line on the shoulder is longer for the 7WSM, preventing accidental chambering or firing of the .284" 7mm bullet in .270 WSM's .277" bore.

The 7mm WSM cartridge achieves its useful purpose as an excellent cartridge for larger mule deer, sheep, black bear and elk.

Winchester claims a muzzle velocity (MV) of 3,225 ft/s with a 140 grain bullet for their 7mm WSM cartridge; the claimed muzzle energy (ME) is 3,233 ft. lbs. With a 160 grain bullet the Winchester figures are 2990 ft/s and 3176 ft. lbs. at the muzzle. The lighter, shorter 7mm bullets are preferred in these short case magnums.

The 7mm WSM has failed to gain the same popularity as the other cartridges in the WSM family. The shortened necks of the cases don't make the 7mm WSM particularly well suited to heavier bullets, limiting the cartridges usefulness on larger game. As well the 7mm WSM shoots about 100 ft/s slower than the 7mm Remington Magnum with heavier bullets.

Cost is another factor limiting popularity. Ammunition prices are higher than that of the 7mm Remington Magnum and of the .280 Remington. Both of which have similar performance to the 7mm WSM, with the 280 Rem having slightly less muzzle energy and the 7mm Rem Mag having slightly more.