Compared: .300 WSM and .300 Win. Mag.

By Chuck Hawks

The .300 Winchester Magnum is the most popular of the many .300 Magnum cartridges, and the only one on the top 10 best selling list of the "big three" U.S. ammunition manufacturers (Federal, Remington, Winchester). The .300 WSM is a short action cartridge intended to equal .300 Win. Mag. ballistics with 150-180 grain bullets. Since Winchester has taken direct aim at their own best selling .300 Magnum cartridge with the new .300 WSM, a comparison seems inevitable.

Since the published ballistics of the two cartridges are so similar, and they can be loaded with identical bullets, there is little point to an extensive ballistic comparison. This article will look primarily at other differences between the two cartridges.

The .300 Winchester Magnum

The .300 Winchester Magnum was introduced to a waiting world in 1963. Unlike previous successful .300 Magnums (.300 H&H, .300 Weatherby), the .300 Win. Mag. was designed for use in standard (.30-06) length actions. There were a lot more standard length rifle actions in the world than long "magnum" actions so, given Winchester's marketing clout, the popularity of the new .300 Winchester cartridge was assured.

The .300 Win. Mag. is based on the .300 H&H case shortened to a case length of 2.62" and a cartridge overall length of 3.34". This is a standard belted case with a rim diameter of .532", very little body taper, a sharp 25 degree shoulder, and a short .264" neck.

The purpose of this design is to maximize powder capacity, allowing the .300 Win. Mag. to outperform other standard length .300 Mag. cartridges and equal or exceed the performance of the .300 H&H Magnum. In fact, the .300 Win. Mag. comes within about 200 fps of the .300 Wby. Mag. with a 180 grain bullet.

The weak point of the design is the very short neck, which makes 200 grain bullets the practical maximum weight. The longer 220-250 grain bullets extend too far into the powder space and defeat the purpose of the cartridge.

Winchester factory loads for the .300 Win. Mag. drive 150 grain bullets at a MV of 3260-3290 fps, 165 grain bullets at a MV of 3120, and 180 grain bullets at a MV of 2960-3070 fps. The Hornady Heavy Magnum factory load drives a 180 grain bullet at a MV of 3100 fps.

Factory ballistics for the .300 Win. Mag. are achieved in 24" test barrels, and most hunting rifles in the caliber come with 24" or 26" barrels, so the advertised ballistics usually check out pretty closely when chronographed in hunting rifles.

For more information about Winchester's Big .30, please see my article "The .300 Winchester Magnum" on the Rifle Cartridge Page.

The .300 WSM

Winchester based their .300 Short Magnum on the .404 Jeffery elephant rifle case, drastically shortened to a case length of 2.1" and a COL of 2.860". The .300 WSM has a rebated rim that will match up to a standard magnum diameter bolt face. It has a very sharp 35 degree shoulder angle. The case neck is slightly less than one bullet diameter, at 0.295" long. The result of these design trade-offs (sharper shoulder, short neck, fat case with rebated rim) is that the .300 WSM has a similar powder capacity to the .300 Win. Mag. case.

For technical reasons fat, short, rebated rim cartridges with very sharp shoulders tend to cause feeding problems from the box magazines typically found in bolt action (and other types of repeating) rifles. This may be why Winchester offers the .300 WSM only in controlled round feed models of their Model 70 rifle. Savage 110's and Browning A-Bolt II's, however, are push feed rifles and they are also available in .300 WSM caliber.

I have received reports from the field of feeding problems with WSM rifles. While these reports are not so frequent that I would necessarily advise against purchasing a .300 WSM rifle, it is something to keep in mind. It is clear that .300 WSM rifles are not as reliable as .300 Win. Mag. rifles because of this problem.

Winchester factory loads for the .300 WSM come with 150 and 180 grain bullets. The 150 grain Ballistic Silvertip bullet has a catalog muzzle velocity (MV) of 3300 fps and muzzle energy (ME) of 3628 ft. lbs. The 180 grain bullets include a Power Point and a premium Fail Safe and both have catalog MV's of 2970 fps and ME's of 3526 ft. lbs. These velocities were developed in 24" test barrels. Federal and Remington also offer .300 WSM loads with 180 grain bullets at similar velocities.

Winchester wisely provides 24" barrels on all .300 WSM caliber rifles. Browning, however, has standardized the somewhat unusual length of 23" for their .300 WSM rifle barrels. The velocity loss in these shorter barrels should amount to about 30 fps, according to Remington estimates. For more information about the .300 WSM please see my article "The .300 WSM" on the Rifle Cartridge Page.

Factory loads

The .300 WSM was designed to give .300 Win. Mag. performance in a short action rifle with bullets of 150-180 grains and, as we have seen above, this it does. There is very little difference between the ballistics of the two calibers as factory loaded.

The difference is in the variety of factory loads available. The .300 Win. Mag. is a worldwide hunting cartridge, and practically all ammunition manufacturers load for the caliber. The 2004 edition of the Shooter's Bible, for example, lists 55 different factory loads for the .300 Win. Mag., in bullet weights of 150, 165, 180, 190, and 200 grains. And those are just the loads commonly encountered in the U.S. They do not include many loads available from European, African and Australian cartridge manufacturers.

The same Shooter's Bible lists exactly 9 factory loads for the .300 WSM, in bullet weights of 150 grains (2) and 180 grains (7) only. The hunter who relies on shooting factory loads could quickly run into trouble if his particular rifle did not provide its best performance with one of those bullet weights or loads.

Clearly, the hunter who shoots a lot of factory loads would do well to choose the .300 Win. Mag. So would the hunter who is planning to hunt on a continent other than North America, as I know of no .300 WSM ammunition being loaded overseas.


There are plenty of bullet choices for any .30 caliber rifle, and the selection is the same for the .300 Win. Mag. or the .300 WSM. The situation is much the same for powders, and both calibers use large rifle magnum primers.

But .300 Win. Mag. brass is much more available than .300 WSM brass. And, in a pinch, .300 Win. Mag. brass can be formed from just about any full length case based on the original .375 H&H belted magnum case, of which there are many. The .300 WSM can be formed only from .404 Jeffery cases, which are very difficult to come by.

Bear in mind that although most reloading manuals show reloads for heavy bullets of 200-220 grains, neither of these cartridges is at its best with heavy bullets. Anyone, and particularly a reloader, purchasing a .300 Magnum rifle for use with heavy bullets should consider a full length magnum cartridge, such as the .300 H&H or .300 Weatherby Magnums.

The .300 Win. Mag. case has slightly greater capacity than the .300 WSM case. The sixth edition of the Hornady Handbook of Cartridge Reloading shows that the .300 Win. Mag. averages about a 50 fps advantage with all bullet weights (110-220 grains).

However, the Hornady .300 Win. Mag. test rifle had a 25" barrel, and the .300 WSM test rifle had a 24" barrel. If we subtract 30 fps from the .300 Win. figures to correct them for a 1" shorter barrel, the velocity advantage becomes 20 fps across the board. If both cartridges are loaded to the same MAP, this is probably indicative of the .300 Win. Magnum's slight advantage in case capacity. On the other hand, many .300 Win. Mag. rifles do have barrels 1"-2" longer than those supplied on .300 WSM rifles, so for these rifles the .300 Win. Magnum's velocity advantage is probably 50-80 fps.

Availability of rifles

The .300 WSM has caught on well for a new cartridge in an already over crowded caliber. Bolt action hunting rifles are available from several major manufacturers including Browning, Ruger, Savage, Winchester, and Weatherby (Vanguard). In addition, Browning offers their BAR autoloader and BLR lever action models in .300 WSM.

On the other hand, almost every model of bolt action rifle that can be chambered for the cartridge is available in .300 Win. Mag. The available rifle models include single shots, a couple of autoloaders, and the aforementioned BLR lever action. No other .300 Magnum cartridge comes close to the .300 Win. in terms of the numbers and variety of available rifles. In availability of rifles, new or used, the .300 Win. Mag. has a clear advantage.


One of the most heavily touted (hypothetical) advantages of the WSM cartridges is their "inherent" accuracy. Unfortunately, this is due more to their resemblance to the short, stubby cartridges popular in the world of bench rest target shooting, rather than any documented advantage in the field.

In the field, the difference between the intrinsic accuracy of these two rifle cartridges is so tiny (if it exists at all) that other factors are overwhelmingly more important. These include, but are not limited to, the rifle (barrel, bedding, action, trigger, care of assembly, etc.), the ammunition (the precision of the various components and the care with which they are assembled), the interaction of the individual rifle with the particular load chosen (hunting ammunition is normally chosen more for its ballistics and terminal performance on game than its accuracy), external conditions (wind, weather, temperature, altitude, etc.), the steadiness of the position from which a shot is fired (from an impromptu rest, prone, sitting, standing, etc.), and most of all the skill of the shooter. Compared to these variables, some of which are huge, any theoretical difference between the intrinsic accuracy of the .300 WSM and .300 Win. Mag. cartridges is absolutely meaningless.

Rifle size and weight

The whole point to the .300 WSM is that it can be used in short action magnum rifles. In the past there have been very few short action rifles with magnum bolt faces, but that is changing. Bolt action rifles from Browning, Remington, Ruger, Savage, Winchester and others are now available for the various short magnum cartridges.

The difference between a standard length action, such as required for the .300 Winchester Magnum, and a short action is about 1/2". Given the same barrel length, stock (length of pull) and so forth, a rifle chambered for the .300 WSM should be about 1/2" shorter than an equivalent rifle in .300 Win. Mag. If the former is, say, 44.5" in overall length with a 24" barrel, the latter should be 44.0" in overall length with a 24" barrel.

Because the short action rifle loses 1/2" out of its middle (action and stock), it is also slightly lighter. This is not always evident from the catalog weight of rifles, since the difference is so slight (usually just a couple of ounces). But other things being equal, it is there. The 2004 Remington catalog shows that their Model 700 BDL SS short magnum rifle with a 24" barrel weighs 7 3/8 pounds, while the standard length magnum version of the same rifle weighs 7 1/2 pounds. That is a 2 ounce difference in weight.

So there is a difference in the overall length and weight of otherwise identical .300 WSM and .300 Win. Mag. rifles. We can estimate that an otherwise identical .300 WSM rifle is about 1/2" shorter and 2 ounces lighter.

The 1/2" shorter length is a slight advantage for the .300 WSM. The difference in weight may or may not be an advantage. For carrying long distances, 2 ounces less weight is a slight advantage. When actually shooting the rifle, particularly during practice sessions at the range, 2 ounces less weight is a slight disadvantage, because less weight means more recoil. The most important thing to remember is that in size and weight there is really not much difference.

Magazine capacity

Because the .300 WSM cartridge is fatter than the .300 Win. Mag. cartridge, an internal box magazine of the type found in most modern bolt action hunting rifles may hold one additional .300 Win. Mag. cartridge. This depends on how the internal volume of a specific magazine compares to the volume occupied by the cartridges. In Savage rifles the .300 WSM magazine capacity is 2 rounds, while the .300 Win. Mag. capacity is 3 rounds. In Winchester M70 rifles the magazine capacity in either caliber is 3 rounds, and in Browning A-Bolt II rifles the magazine capacity in either caliber is 4 rounds.

CXP2 and CXP3 game

In terms of effectiveness (killing power) on typical CXP2 game, such as deer, antelope, goats, wart hog, wild sheep, feral hogs, black bear, red stag, and caribou there is no practical difference between the .300 WSM and .300 Win. Mag. Nor is there any difference between the two cartridges when larger CXP3 class game is the quarry. Examples of typical CXP3 game include Scandinavian moose (alg), North American moose, Rocky Mountain elk, Roosevelt elk, zebra, kudu, and wildebeest.

None of these animals are normally classed as dangerous game, and all can be humanely killed by a single well placed bullet from any .300 Magnum rifle. Should a malfunction occur, which is unlikely in any case, a trophy may be lost but no real harm is done. It is not a life and death matter.

Dangerous game

Hunting dangerous game, on the other hand, is an entirely different matter. I would not recommend the .300 WSM cartridge for hunting any type of dangerous game. The ballistics of the .300 WSM and .300 Win. Mag. are undoubtedly sufficient for all of the big predators (cats and bears). Many Alaskan brown bears and African lions, for example, have been taken with .300 Magnum rifles.

But it would be foolish to choose a rifle in .300 WSM when the same or a similar rifle is available in .300 Win. Mag. Even though the statistical difference in feed reliability is slight, it does exist. And anyone hunting dangerous game owes it to himself and to his tracker, guide, or some innocent person who may later cross a wounded animal's path, to eliminate all possible risk. A failure to feed when a follow-up shot is needed could potentially have disastrous consequences. Hunting dangerous game is a life and death matter, and it is often not the hunter, but a bystander, who is killed.


Any .300 Magnum rifle kicks more than most shooters can stand. A great many .300 Magnum fans won't admit it, but practically anyone can shoot better with a rifle that kicks less. And bullet placement is the most important factor in killing power. Literally any animal that can be killed by a well placed bullet from a .300 Magnum can also be killed by an equally well placed bullet from a .30-06. A point to remember before you buy that new .300.

It has been alleged that the .300 WSM kicks less for the same bullet weight at the same MV than the .300 Win. Mag. This is supposed to be due to its "more efficient powder burn." So just how much difference is there in recoil between the .300 WSM and .300 Win. Mag.?

Since we have already acknowledged that the .300 Win. Mag. has a slightly greater powder capacity, we can assume that this will contribute to increased recoil. The more powder you burn, the more recoil you generate.

On the other side, we have also acknowledged that in otherwise identical rifles the .300 WSM should weigh about 1/8 pound less, and the lighter the rifle the more it kicks. Let's see how these factors average out.

Lets say that our typical .300 WSM rifle weighs 8 pounds 6 ounces (8 3/8 pounds), and our typical .300 Win. Mag. rifle weighs 8 pounds 8 ounces (8 1/2 pounds), both with identical 1 pound scopes and mounts. .300 WSM factory loads are available in two bullet weights, 150 and 180 grains, so let's compare those two bullet weights. To be as fair as possible, let's compare those two bullet weights at identical velocities, using the same powders.

According to the sixth edition of the Hornady Handbook, 69.5 grains of H4350 powder can drive a 150 grain bullet to a MV of 3200 fps in the .300 WSM. (No powder listed can duplicate the MV of 3300 fps claimed for the 150 grain factory load in the WSM, although 5 different powders can achieve 3300 fps in the .300 Win. Mag.) And 70.8 grains of H4350 can drive a 150 grain bullet to 3200 fps in the .300 Win. Mag.

AA Magpro is the only powder listed in the Hornady Handbook that can drive 180 grain bullets to a MV of 3000 fps in both cartridges, duplicating the 180 grain factory loads. It takes 80.0 grains of powder in the .300 WSM and 76.9 grains in the .300 Win. Mag.

Using those loads for comparison, here are the recoil energy figures:

  • .300 WSM, 150 grain at 3200 fps = 24.6 ft. lbs.
  • .300 Win Mag, 150 grain at 3200 fps = 24.6 ft. lbs.
  • .300 WSM, 180 grain at 3000 fps = 31.8 ft. lbs.
  • .300 Win Mag, 180 grain at 3000 fps = 30.3 ft. lbs.

Looking at those numbers, I would have to say that there is no significant difference in the recoil of the two cartridges. What happened to the alleged "more efficient powder burn" in the .300 WSM I could not say.


In several categories the two cartridges are essentially equal. In others the .300 Win. Mag. emerged the clear winner. Only in overall rifle length was the .300 WSM clearly superior (shorter), and then by only 1/2". Whether that 1/2" in rifle length is sufficient reason to select a cartridge that is inferior, or at best merely equal, in every other respect I leave to you to decide.

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