.325 WSM

.325 Winchester Short Magnum (also known as .325 WSM, commonly pronounced as "Whizzum") is a 8 mm (.323 in) caliber rebated rim bottlenecked centerfire short magnum cartridge that was introduced in 2005 by Winchester Repeating Arms Company. It is a member of the Winchester Short Magnum family of rifle cartridges.

The .325 WSM was designed to take on the thick-skinned and heavy-shouldered big game animals found from Alaska to Africa. Combining the velocity of the .300 Winchester Magnum with the knockdown power of the .338 Winchester Magnum, the .325 WSM offers the power needed to take on big game animals in a lighter short action rifle. Like all .300, 8 mm and .338-caliber magnum cartridges the .325 WSM can not be universally used on African game since certain sub-Saharan Africa countries have a 9.53 mm (.375 in) minimum caliber rule for hunting Big Five game.

Cartridge dimensions
The .325 WSM has 5.39 ml (83 grain) H2O cartridge case capacity.



.325 WSM maximum cartridge dimensions. All sizes in millimetres (mm).

Americans would define the shoulder angle at alpha/2 = 35 degrees. The common rifling twist rate for this cartridge is 254 mm (1 in 10 in), 6 grooves, Ø lands = 8.00 mm, Ø grooves = 8.20 mm, land width = 3.10 mm and the primer type is large rifle magnum.

According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) guidelines the Winchester Short Magnum family of rifle cartridges can handle up to 445 MPa (64542 psi) piezo pressure. In CIP regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum CIP pressure to certify for sale to consumers.

The .325 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 German 8 x 68 S cartridge introduced in 1939 is probably the closest ballistic twin of the .325 WSM. The .325 WSM is considerably shorter and fatter and has a more radical rebated rim, much steeper shoulder angle and a shorter neck (7.82 mm) than the 8 x 68 S. This makes the 8 x 68 S case with its 9.11 mm long neck better suited for loading long heavier bullets and due to its sleeker exterior shape bound to cycle more reliable in bolt action rifles in extreme situations. On the other hand the proportions of .325 WSM promote good internal ballistic efficiency that makes that the .325 WSM can fire shorter lighter bullets at slightly higher muzzle velocities whilst using less propellant than the classically proportioned 8 x 68 S.

8 mm cartridges compared
Maximum muzzle velocity comparison in % of the probably most proliferated European and American 8 mm rifle cartridges out of 650 mm (25.59 in) long barrels loaded with relatively light to heavy 8 mm bullets to their CIP or SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) sanctioned maximum pressures.

This comparison is not totally objective since the 8 mm Remington Magnum and .325 WSM operate at 445 MPa (65000 psi), the 8 x 68 S at 440 MPa (63817 psi), the 8 x 64 S at 405 MPa (58740 psi) and the 7.92 x 57 mm Mauser at 390 MPa (56564 psi) maximum chamber pressure. Higher chamber pressure results in higher muzzle velocities.

Categories
Cartridge:rifles