Reloading the .25 WSSM
March 03, 2011
Back when the Earth was flat and I still had hair, the term "short magnum" meant a cartridge based on the .300 H&H Magnum case whacked off to about 2½ inches. No more. 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 by the .270, 7mm and .325 WSMs. These are loosely based on the .404 Jeffery case shortened to 2.1 inches, and they have a body diameter of .555 inch — bigger than the belt of the older H&H case.
In the mid-1990s Winchester stunned the shooting world with another 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. Our test gun this month was a production K8-MAG in .25 WSSM sporting a 24-inch barrel with a 1:10 twist.
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 — obviously too long for an AR magazine — so bullets in handloads must be seated to 2¼ inches to feed properly. And, no, 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. All of the test loads reported here were loaded to 2¼ inches, and functioning was 100 percent.
Handloading the .25 WSSM is about like any other bottlenecked rifle round. The only problem that surfaced during testing was 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.
Now that we've gotten that out of the way, let's get down to loading. I used a set of Redding dies to prepare the test loads. 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. I used Winchester WLRs for all loads save one, which was started by CCI-250 magnum caps, and all worked perfectly.
A wide variety of powders such as H-4350, Reloders 17 and 19, Varget, Hunter and W-760 worked well in the .25 WSSM. IMR-4007SSC was a standout in the semiauto with several loads.
While this cartridge can certainty be used for varmints, probably 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. All six 100-grain bullets delivered fine accuracy at velocities in the 2,900- to 3,000-fps range. The Speer Hot-Cor with 47.0 grains of H-4350 was barely shy of the 3,000 fps mark and turned in 1¼ -inch groups. Hornady's 110-grain InterBond and 46.3 grains of Reloder-19 yielded .74-inch groups and a 2,824 fps average.
Moving up in bullet weight leads to the 115- and 117-grain spitzer boattails from Nosler, Hornady and Sierra, and each excelled with the selected handload. A top pick would be the 115-grain Ballistic Tip over 37.2 grains of Varget. The velocity of this load is a modest 2,679 fps, but groups averaged .71 inch.
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.
Time will tell if the .25 WSSM will win the hearts of American shooters. But one thing's clear. With the proper loads, the .25 WSSM can hold its own in power, accuracy and reliability in an AR.