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Reloading The .25 WSSM

In the former days of shooting and ammunition, the term “short magnum” meant a cartridge based on the .300 H&H Magnum case cut down to about 2½ inches. Nowadays, there are lots of “short magnums” with case lengths and diameters all over the place. In 2001, Winchester introduced the .300 WSM, followed soon after by the .270, 7mm and .325 WSMs. These are loosely based on the .404 Jeffery case shortened to 2.1 inches and have a body diameter of .555 inch.

In the mid-1990s Winchester introduced a trio of short magnums in .223, .243 and .25. Called Winchester Super Short Magnums, their cases are the same diameter as the WSMs, but only 1.670 inches in length.

The .25 WSSM was designed to duplicate the .25-06, and in some instance, it does. With 100- to 120-grain bullets, velocities approach that threshold, but the newer cartridge can do so only by operating at higher pressures—65,000 psi compared with the .25-06’s 53,000 psi. The main vehicles for the .25 WSSM were the Browning A-Bolt and Winchester Model 70. Unfortunately, both have been discontinued. Thus, the seeker of a bolt-action .25 WSSM must scour the used-gun market.

Olympic Arms Company produces an extensive line of ARs in a host of calibers, and its Model K8-MAG is offered in the three WSSMs noted above. The K8-MAG comes with a 10-round magazine, which is actually a modified 5.56 AR magazine, and it functioned 100 percent—as long as the cartridge’s OAL was right.

Maximum length for the .25 WSSM is roughly 2.700 inches, which is too long for an AR mag. Therefore, bullets in handloads must be seated to 2¼ inches to feed properly. Factory loads at 2.34 inches in length won’t work in the K8-MAG. This is, of course, of little consequence for the handloader.

Handloading the .25 WSSM is about like any other bottlenecked rifle round. The main problem you might occur is case life. The drastic reduction in diameter required to form the .25 WSSM case seriously work-hardens the neck and shoulder areas, and split cases are frequent after a few firings.

One could easily solve this problem by annealing, of course. It should also be noted that the necks of this case are somewhat thicker (at .021 inch) than some other .25-caliber cartridges, such as the .257 Roberts and .25-06 at .0165 inch. This makes seating bullets in a new case difficult unless the inside of the case neck is polished and/or lubed prior to bullet seating. Lightly chamfering the case mouth is also recommended.


The correct shell holder is the same one used for the WSMs. Don’t over-lube, or dents will occur in the case’s 30-degree shoulder. Even though the .25 WSSM is a “magnum,” its modest case capacity really calls for standard primers.

While this cartridge can certainly be used for varmints, few will lay down an extended barrage in a dog town with it. For low-volume, long-range shooting, the 87-grain Sierra SPT at 3,036 fps over 47.5 grains of Big Game makes a serious coyote load, however.

The .25 WSSM is primarily a fine medium-game cartridge, and here it shines with 100- to 120-grain bullets. Moving up in bullet weight leads to the 115- and 117-grain spitzer boat tails from Nosler, Hornady and Sierra, and each excell with the selected handload.

The 120-grain, controlled-expansion bullets are for larger game. Nosler’s 120-grain Partition zipped along at 2,771 fps with 43.0 grains of Reloder 17. The 120-grain Speer Grand Slam, in front of 44.1 grains of H-4350, clocked over 2,700 fps and groups were under an inch. Speer’s 120-grain Hot-Cor continues to carry its share of the load. With 39.3 grains of Ball-C (2), it cruised at 2,642 fps and punched 1½-inch groups.