Compared: The .25 WSSM and .257 Weatherby Magnum

By Chuck Hawks

This comparison is not my fault! If Winchester had named their Winchester Super Short Magnum (WSSM) line of cartridges "WSSC" for "Winchester Super Short Cartridge" I would have no quarrel with them. For, you see, the word "magnum" as applied to rifle cartridges implies a larger than normal case, just as it does in wine bottles, not a smaller one.

But, since they insist that the .25 WSSM is a magnum rifle cartridge, it must be compared with other .25 caliber magnum rifle cartridges, the best known of which is the .257 Weatherby Magnum.

Both the .25 WSSM and .257 Wby. Mag. are at their best with bullets weighing between 115 and 120 grains. Both cartridges use the same .257" diameter bullets.

Incidentally, because the .257 Weatherby was shortened enough to fit in a standard (.30-06) length action and the .300 H&H parent cartridge requires a longer "magnum" length action, the .257 Weatherby was once referred to as a "short magnum." So I guess in this article I am comparing the original short .25 magnum to a newer and even shorter .25 magnum.

Can the .25 WSSM run with the big dogs? Can it live up to its magnum label? We are about to find out.

The .257 Weatherby Magnum

The .257 Weatherby Magnum was introduced in 1944 as a proprietary cartridge based a necked-down .270 Wby. case. The .270 Wby. Mag. was itself based on a shortened and blown-out .300 H&H Magnum case. The .257 retains the standard belted rimless case configuration of the .270 and .300 Magnums and uses the unique Weatherby double radius venturi shoulder design.

Weatherby offers six factory loads for their .257 Magnum. The varmint load drives an 87 grain Hornady Spire Point bullet at a muzzle velocity (MV) of 3825 fps. For CXP2 class (medium) game such as deer, sheep, pronghorn, and black bear Weatherby offers a 100 grain Hornady Interlock Spire Point bullet at a MV of 3602 fps, 115 grain Nosler Ballistic Tip and Barnes-X bullets at a MV of 3400 fps, a 117 grain Hornady Interlock RN bullet at a MV of 3402 fps, and a 120 grain Nosler Partition bullet at a MV of 3305 fps.

Weatherby offers the .257 Magnum in several of their Mark V rifle models as well as their more economical Vanguard line. All Mark V .257 rifles are supplied with 26" barrels as of this writing; Vanguards come with 24" tubes. Although it clearly has ultra-long range varminting capabilities, the .257 is primarily a big game cartridge and Weatherby does not offer it in their Super VarmintMaster models.

The .25 WSSM

Winchester introduced the .25 WSSM 60 years after the design of the .257 Weatherby. It is based on a necked-up .243 WSSM case with a slightly sharper 30 degree shoulder. They offer a Supreme varmint load that drives an 85 grain Nosler Ballistic Silvertip bullet at a MV of 3470 fps. Winchester offers two loads for the .25 WSSM intended for hunting CXP2 class game. One of these is a Supreme 115 grain Ballistic Silvertip bullet at a MV of 3060 fps. The other is a Super-X load using a 120 grain Positive Expanding Point bullet at a MV of 2990 fps. This should be the best .25 WSSM load for North American mule deer, sheep, mountain goats, black bear, and other game of similar size.

Browning and Winchester make special super short actions for the WSSM series of cartridges. Big game and varmint style rifles are offered. The varmint models come with 24" barrels; the sporter versions of the Browning A-Bolt II come with 21" barrels and the sporter versions of the Model 70 come with a 22" barrels.


As we have already seen, the .257 Wby. Mag. has a big velocity advantage over the .25 WSSM. With the 85-87 grain varmint bullets the difference in MV is 355 fps. With 115 grain bullets the Weatherby's velocity advantage is 340 fps. And with the 120 grain bullet, the difference in MV is 315 fps in favor of the .257 Wby. This is an enormous velocity disparity between what are alleged to be magnum cartridges of the same caliber. Maybe WSSM really stands for "Winchester Super Slow Magnum."


Since both cartridges use the same weight bullets, and the .257 Weatherby shoots them a lot faster, it stands to reason that the .257 will also deliver more kinetic energy to the target. Reason, in this case, is correct. Energy matters in a big game hunting cartridge because it is a prime component of killing power. Here is an energy comparison in foot pounds for the two primary weights of big game bullets as factory loaded at the muzzle (ME) and at 200 yards.

  • .25 WSSM, 115 grain bullet: ME 2392 ft. lbs.; 200 yds. 1778 ft. lbs.
  • .257 Wby., 115 grain bullet: ME 2952 ft. lbs.; 200 yds. 2226 ft. lbs.
  • .25 WSSM, 120 grain bullet: ME 2383 ft. lbs.; 200 yds. 1612 ft. lbs.
  • .257 Wby., 120 grain bullet: ME 2910 ft. lbs.; 200 yds. 2091 ft. lbs.

Once again the comparison is very one sided. The .257 Weatherby exceeds the .25 WSSM in energy at the muzzle by an average of 543.5 ft. lbs. The .257 Weatherby exceeds the .25 WSSM in energy at 200 yards by an average of 463.5 ft lbs. The difference in energy is huge.


Loaded to the maximum permissible pressure the .257 Weatherby shoots flatter with the same weight bullet than the .25 WSSM because it has significantly greater powder capacity and also operates at slightly higher pressure (53,500 cup compared to 52,000 cup). For example, comparing identical 120 grain bullets (BC .391) in both calibers at claimed factory load MV, we can see on the "Expanded Rifle Trajectory Table" that the .257 Wby. factory load has a maximum point blank range (+/- 3") of 317 yards, compared to a MPBR of only 291 yards for the .25 WSSM.

Using the maximum point blank range shows the optimum trajectories for both cartridges. Using a 200 yard zero for both cartridges and calculating the drop at longer range (as Winchester does in their ballistics tables) would simply magnify the difference between the two cartridges, making the .257 Weatherby look even better.

The real world difference between the two cartridges is even more pronounced. All Weatherby Mark V rifles are supplied with 26" barrels, the length for which Weatherby factory ballistics are developed. Winchester factory ballistics for the .25 WSSM were developed in 24" barrels, but Winchester Model 70 hunting rifles actually come with 22" barrels. The resulting velocity loss means that the 120 grain .25 WSSM factory load does not come close to its advertised velocity and trajectory in the field. The 120 grain Winchester factory load was reported (by David M. Fortier in Shooting Times magazine) to actually chronograph 2834 fps from a Model 70. That lowers its MPBR to only 273 yards, which can not in any way be called magnum performance.

So while the .257 Weatherby Magnum is a true ultra-long range rifle, and one of the flattest shooting calibers on the market, the .25 WSSM barely qualifies as a long range caliber at all. Its MPBR with a 120 grain bullet is actually very similar to that of the .257 Roberts (271 yards).

Killing power (Optimal Game Weight)

Next, let's take a look at the .25 WSSM and .257 Weatherby Magnum in terms of killing power. A 120 grain bullet is probably the best alternative for the largest game that one might choose to hunt with any .25 caliber magnum cartridge. This heavier bullet with its sectional density of .260 is what gives the big case .25's their margin of superiority over the .24/6mm class of cartridges.

According to the "Expanded Optimal Game Weight" table, with identical 120 grain bullets at factory load velocities the maximum optimal range on 400 pound game is: 130 yards for the .25 WSSM, and 280 yards for the .257 Weatherby Magnum. The Weatherby cartridge offers over twice the optimum killing range of the WSSM cartridge!

Overall performance

In terms of performance, no matter what you look at (velocity, energy, trajectory, or killing power), the .257 Weatherby Magnum is superior to the .25 WSSM. Since the .257 has greater case capacity and has a slightly higher maximum average pressure limit, it can be no other way. It is literally impossible for the .25 WSSM to equal the performance of the .257 Weatherby Magnum with full power loads, whether factory loads or reloads.

That is understandable and, frankly, expected. What is unexpected is the extent of the performance gap between the two cartridges. Surely Winchester could (and should) have made a similar comparison while developing their .25 caliber "magnum." Perhaps then they would have reconsidered their plans.

Clearly the larger .270 WSM case would have been a better choice as the basis for a proposed .25 Magnum. Even then the .257 Weatherby would have an advantage, but at least the gulf between the performance of the two cartridges would not be so embarrassingly wide.

Other factors

Leaving aside performance, which is pretty hard as performance is what magnum rifle cartridges are supposed to be about, let's take a brief look at other factors that may at least partially redeem the .25 WSSM. These include accuracy, the rifles in which the cartridges are chambered, reliability and recoil.


Short, fat rifle cartridges like the .25 WSSM are supposed to have excellent inherent accuracy. Winchester claims in their advertising that this is true. Of course, Weatherby advertising also claims superior accuracy for their rifles and ammunition.

I have always held that other factors, such as the quality of the rifle and the loads fired in it, are far more important to accuracy than the shape of the cartridge case. And that appears to be the situation here, for Browning and Winchester make no accuracy guarantee of any kind for their .25 WSSM rifles and ammunition.

But Weatherby not only claims superior accuracy for their rifles and cartridges, they guarantee that every Weatherby .257 Magnum rifle will deliver 1.5" 3-shot groups at 100 yards with Weatherby factory loaded ammunition. ("However, it is common for Weatherby rifles to shoot much tighter groups straight out of the box.") Apparently Weatherby has more confidence in their advertising claims than does Winchester.

No bonus point for the .25 WSSM in accuracy. In fact, it is the .257 Weatherby Magnum that gets the bonus point for accuracy, guaranteed!


The little .25 WSSM cartridge is supposed to be a natural for light weight, easy to carry rifles. After all, it uses an action about an inch shorter than the standard length action required for the .257 Weatherby Magnum cartridge. The Model 70 Ultimate Shadow with a composite stock weighs 6.5 pounds in .25 WSSM, and the Model 70 Featherweight with its walnut stock weighs only 6 pounds. And that is, indeed, a lightweight rifle. Both of these rifles come with 22" barrels.

But the Weatherby Ultra Lightweight and Super Big Game Master Mark V rifles in .257 Wby. Mag. weigh only 6.75 pounds, and come with 26" barrels. Those are the Weatherby models most similar to the Winchester Ultimate Shadow.

That's a 4" longer barrel, the heaviest component of any rifle, and the weight of the Weatherby rifles, including the longer action, is only 4 ounces greater than the Ultimate Shadow! Maybe the super-short action really doesn't make all that much difference in the total weight of a rifle. Perhaps the weight of other components such as the stock and barrel (not to mention a scope and mount) are far more important.


One factor that certainly isn't going to favor the .25 WSSM is reliability. The same shape that is supposed to make the cartridge slightly more accurate (if all other factors are equal, which they never are) undeniably makes it less reliable.

The design of the two cartridges should be touched on briefly as it relates to use in hunting rifles. The .257 Weatherby is a normally proportioned, modern hunting cartridge of proven feed reliability in bolt action rifles. On the other hand the extremely short and fat, sharp shouldered, rebated rim .25 WSSM is a nightmare shape in terms of feed reliability. It looks like a jumbo size bench rest cartridge of the 6mm PPC type, and they are intended for use only in single shot rifles.

Short and fat is the worst possible cartridge geometry in terms of feed reliability. When every shot counts . . . the smart money is on the .257 Weatherby Magnum.


I can practically guarantee that the recoil of a typical .25 WSSM rifle will be less than the recoil of a typical .257 Weatherby rifle. Recoil is a function of the total mass expelled from the muzzle of a rifle (bullet and powder gasses) moderated by the weight of the rifle. The extra weight of the Weatherby rifles is not going to overcome the fact that the bigger .257 Weatherby Magnum case holds a lot more powder than the .25 WSSM case.

The "Expanded Rifle Recoil Table" credits the .25 WSSM with the 120 grain factory load with a recoil energy of 13.8 ft. lbs. in a rifle with a total weight (including scope) of 7.25 pounds. The same table credits the .257 Weatherby Magnum with recoil energy of 15.1 ft. lbs. from a rifle (such as a Weatherby Mark V Deluxe) with an all-up weight of 9.25 pounds. The recoil figure for the .257 Mag. would be higher in a Weatherby Ultra Lightweight rifle.

No question that the .25 WSSM kicks less than the .257 Wby. Mag. in rifles of the same weight. Since the .25 WSSM doesn't perform like a magnum cartridge, it doesn't kick like one, either.

Other .25 caliber cartridges & Conclusion

To put the .25 WSSM and .257 Weatherby Magnum in proper perspective, let's compare the muzzle velocity of five of the best known .25 caliber cartridges using full power loads with 117-120 grain bullets in barrels of typical length. The list would look something like this:

  1. .257 Weatherby Magnum (26" brl.) - MV 3305 fps.
  2. .257 Weatherby Magnum (24" brl.) - MV 3200 fps.
  3. (tie) .25-06 Remington & .25 WSSM (24" brl.) - 2990 fps
  4. .257 Roberts Improved (24" brl.) - 2900 fps.
  5. .25 WSSM (22" brl.) - 2834 fps.
  6. .257 Roberts +P (24" brl.) - 2780 fps.

It is clear that the only real .25 caliber magnum on the list is the .257 Weatherby. Its performance is clearly superior to the other four cartridges, occupying the first two places. It is also apparent that the .25 WSSM offers good, but not magnum, performance compared to the standard .25 caliber cartridges. Its advertised ballistics put it in a tie for third place, and its real world ballistics put it in fifth place (out of 6). I guess that is as good a summary as any of the comparison between the .25 WSSM and the .257 Weatherby Magnum.

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Copyright 2004, 2012 by Chuck Hawks. All rights reserved.