The 300 WSM
By Ron Spomer

Ron Spomer Outdoors Baker's doz. 30 cals.


The 300 Winchester Short Magnum (fourth from right) is magic. Or so goes the advertising hype. This short, fat case is supposed to match the ballistics of the old, long 300 Win. Mag. (fifth from right) while burning 10 percent less powder; cycle through shorter, lighter rifles; be more accurate; recoil less and kill like lightning crossed with the hammer of Thor.


Well, sort of.


While the 300 WSM, sprung on an unsuspecting public in 2000, is indeed one fine, efficient cartridge, its biggest magic is the enthusiastic press it’s generated. Shooters are smitten. But should they be?


Perhaps. For decades our biggest, fastest magnums have been based on the long, belted H&H magnum case (sixth from right), which is the parent case for the 300 Winchester Magnum, the 7mm Rem. Mag., 264 Win. Mag., most of the
Weatherby Magnums and more. All use the H&H .532 inch diameter head and .511 inch diameter body. The 300 WSM body is closer to the dimensions of the much fatter 404 Jeffery case. And, like the Jeffery, it has no belt.


Body diameter at the base is .555 and it barely tapers over the 1.464-inch run to the start of the 35-degree shoulder. This creates a storage reservoir for a considerable quantity of powder in a cartridge with an overall length of 2.86 inches, just a smidge longer than the .308 Winchester (fourth from left.) That means the 300 WSM does indeed cycle through short-action rifles, and those are always ballyhooed as being shorter, lighter, stiffer and faster to cycle than standard or magnum length actions. All true. But of dubious value in hunting rifles.


All else being equal, a short-action rifle will weigh two to four ounces less than its equivalent standard action (30-06 length, seventh from right), perhaps six to eight ounces lighter than an H&H full magnum length (300 Wby. Mag, third from right.) How much time is saved in bolting in a follow-up shot? Who knows. Micro seconds. Once you get used to cycling your action, regardless its length, it’s no big deal. You can, however, get into trouble if your muscle memory is keyed to a short action and you switch to a long. You might short-stroke it and fail to bring a new round into battery. So there is an argument for consistency if you own more than one rifle. But should you sell a magnum action rifle just to gain recycling speed? I wouldn’t.


The stiffness inherent in a shorter action can contribute to accuracy because it reduces vibrations and flexing. Flex in the action can result in slight bending of the bolt/breech lock-up and alignment of the cartridge in the chamber. Solid, consistent bedding of the action against the stock nullifies such flex. But you’re not likely to notice or benefit from this unless you’re trying to shave .001 inch off your target group.


For hunting, don’t worry about it.


That takes us to efficiency and reduced recoil. It does appear to be true that the .300 WSM is more efficient than its longer magnum cousin. Handloading manuals show recipes calling for 5 to 10 percent less powder in the WSM to match velocities in the 300 Win. Mag. More efficient burning in the sharp-shouldered case is usually credited for the efficiency gain. You won’t see this reduced powder charge reflected in factory ammunition prices, but if you handload and shoot hundreds of rounds a year, you can save a few dollars with the 300 WSM. The reduced recoil -- if Newton of apple-falling fame was correct in his prediction that for every action there is an opposite, equal reaction – will be slightly less in the WSM because there may be 5 to 7 fewer grains of powder. Personally, I don’t believe I can feel this difference, but many WSM lovers swear they do.


Even without the hype, the 300 WSM is a fine, efficient cartridge for throwing 150- to 180-grain .308 bullets at 3,300 to 3,080 fps. That’s good enough for anything short of elephants and I wouldn’t bet against it there. For North America the 300 WSM is a superb, no-questions-asked, do-it-all cartridge. A bit excessive for pronghorns and small whitetails, for sure, but, as someone once said, they can’t be too dead. A 150-grain spire point sighted at 200 yards will drop just 5.4 inches at 300 yards, 16 inches at 400 yards and carry 2,200- and 1,900 ft. lbs. respectively. Elk, moose and grizzlies won’t like that. Free recoil energy in an 8-pound rifle should be around 24 ft. lbs. Compare this to 19 ft. lbs. with the same bullet from a .30-06. Due to the sharp shoulder of the WSM case, handloaders should rarely have to trim these cases.


All things considered, the 300 WSM is one heck of a cartridge. If you’ve been hankering for a .308 magnum, this could be it. If you already have a 300 Win. Mag. or Weatherby Mag., you won’t gain anything but the thrill of a new rifle. And that’s excuse enough for some of us.


P.S.  The big cartridge on the far right is the 30-388 Wby. Mag. Next to it is the 300 Rem. Ultra Mag. The stubby one on far left is the 30 Remington, a handloading option. Next in line is the 30-30 Win., then 300 Savage, 308 Win., 30 TC and 308 Marlin. Do you think we have sufficient 30 caliber options?

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