The Evolution of Magnum Rifle Cartridges
By Chuck Hawks
The "magnum" concept as applied to wine indicates an outsize bottle. As applied to rifle cartridges it implies a larger than standard case. Until recently, magnum rifle cartridge cases headspaced on a belt at the head of the case. The presence of such a belt, in the collective mind of the shooting public, indicted a magnum cartridge.
The British firm of Holland & Holland pioneered magnum rifle cartridges. The first of these was the .375 H&H Magnum, introduced in 1912 and still going strong today. The .375 H&H was a true magnum cartridge in that it was based on a big case and delivered higher ballistic performance than previous cartridges of the same caliber. It also introduced the belt as a method of positively maintaining correct headspace. The big .375 Magnum case is 2.850" long with a rim/belt diameter of .532" and a base diameter of .513". For years these dimensions were common to all magnum rifle cartridge cases.
Holland & Holland followed the success of their .375 with .300 and .244 caliber cartridges based on the same case. H&H also introduced a .275 (7mm) Belted Magnum cartridge on a shortened version of the .375 case that measured 2.500" in length. And, in the 1920's, a smaller belted case with a rim/belt diameter of .467", base diameter of .450", and case length of 2.490" for their .240 Magnum Rimless.
Thus, from the originator of the modern magnum rifle cartridge, we see all of the trends to downsize that have more recently so muddied the magnum waters. But, note that the two things all of these H&H Magnums had in common when introduced was performance superior to standard (non-magnum) rifle cartridges of the same caliber and a belted case.
In North America in the mid-1940's, Roy Weatherby experimented with shortening, necking down, and blowing out the .300 H&H belted case to produce his .257, .270, and 7mm Weatherby Magnums. He used the full length H&H case fire formed for greater capacity for his .300, .340 and .375 Weatherby Magnums. All Weatherby Magnum cases use a sharp, double radius shoulder. The .257, .270, and 7mm Weatherby Magnums have a case length of 2.549" and an overall cartridge length that allows them to feed and function in standard (.30-06) length rifle actions. The .300, .340, and .375 Weatherby Magnums, with a case length of 2.825", require a long or "magnum" (.375 H&H) length rifle action.
The cartridges that Roy Weatherby developed in the 1940's and 1950's set the standard for the development of most other magnum cartridges. All offered substantially increased performance compared to standard rifle cartridges of the same caliber.
Subsequent magnum rifle cartridges that followed the same basic principles were the 7x61mm S&H, .308 and .358 Norma Magnums, .264, .300, .338, and .458 Winchester Magnums, and the 7mm, 8mm, and .416 Remington Magnums. All of these are based on a blown out .375 H&H case. All but the 8mm and .416 Rem. Magnums are shortened to function in standard length rifle actions. They outperform previous standard cartridges such as the 6.5x55, .280 Remington, .30-06, 8x57, .33 Winchester, and .35 Whelen.
The .416 and .458 Magnums are specialized cartridges for use on thick-skinned dangerous game. The .458 Win. Mag. was designed to duplicate the performance of the British .450 Nitro Express elephant cartridge in a modern offering that would function in standard length bolt action rifles. ("Express" was a British term used to denote a more powerful version of a cartridge; the predecessor of "Magnum.") The later .416 Rem. Mag. was designed to provide .416 Rigby ballistics in a conventional magnum format.
In 1965 Remington introduced the first true "short magnum" cartridge, the .350 Remington Magnum, based on a shortened and necked-up version of their 7mm Rem. Mag. case. The intent of the .350 was to exceed the ballistics of the previous .358 Winchester in a cartridge of similar overall length. Like the .358, the .350 Mag. and its running mate the 6.5mm Remington Magnum (which handily exceeds the performance of the 6.5x55) were designed to function in short (.308 Winchester) length rifle actions. The basic blown out .375 H&H case had been shortened to only 2.170" in length and the length of magnum cartridges had reached its practical minimum.
Commercially the .350 was not very successful, although it handily outperformed the .358 Win. Gun writers compared the .350 to the wildcat .35 Whelen, the .30-06 case necked-up to accept .358" bullets and for which no pressure standards existed, and condemned it for only equaling the wildcat's performance. In fact, the fuss that erupted over the .350 Rem. Mag. in the gun magazines of the time created a demand for a SAAMI standardized version of the .35 Whelen, which Remington provided in 1987. How times (not to mention the integrity of the firearms press) have changed! But more on that later.
Weatherby pioneered what I call the "super magnum" when Roy designed a belted version of the .416 Rigby elephant rifle case, gave it a double radius shoulder, and necked it to accept .375" bullets, thus creating the .378 Weatherby Magnum. The same case was later necked-up to become the .416 and .460 Weatherby Magnums and down to become the .30-378 and .338-378 Weatherby Magnums. These monsters have a .579" rim diameter, .603" belt diameter, .582" base diameter, and a 2.913" case length. All of these cartridges substantially out perform equivalent caliber magnums based on the full length .375 H&H case.
Remington got into the super magnum business when they introduced their line of Ultra Mag cartridges in 1999. These are full (.375 H&H) length magnums based on the big .404 Jeffery elephant cartridge case. The rim diameter of the Ultra Mags is .534" so that they will mate to the bolt faces of existing magnum actions, but the base diameter is .550". This makes the Ultra Mags rebated rim cartridges, and they lack the familiar magnum belt. The Ultra Mag cartridges headspace on the shoulder. The intent of the Remington Ultra Mag series is to outperform the magnum cartridges based on the .375 H&H case.
Nearly simultaneously with the development of the Ultra Mag super magnums, Remington engineers and technicians were also working on a drastically shortened version of their new case, intended to function in short action rifles. This was to be a new line of short action magnums with a very different design goal: merely equaling, not exceeding, the performance of the previous generation of standard length magnum cartridges. Specifically, the popular 7mm Remington and .300 Winchester Magnums defined the performance goals of the new Remington Short Action Ultra Mag (SAUM) cartridges.
About the same time, after a long hiatus in the introduction of new magnum cartridges, Winchester kicked over the traces in 2001 by introducing their line of WSM (Winchester Short Magnum) cartridges. The .300 WSM and 7mm WSM had exactly the same design goal as the Remington .300 and 7mm Short Action Ultra Mags, and were also based on a drastically shortened version of the .404 Jeffery case. Winchester got the first of their short action magnums to market about six months ahead of the Remington SAUMs, securing a lead in sales that they have maintained to this day.
Winchester also made a very smart move by introducing a .270 WSM cartridge. There has been a market for a short action .270 for generations, and the .270 WSM fills that need. It is also the only one of the new generation of short magnum cartridges that even pretends to exceed the performance of an existing cartridge.
I understand that Winchester had hoped to further extend their WSM line to include .25 and .338 caliber short magnums. Unfortunately, the much-touted "short/fat" case geometry proved to be severely limited in versatility. 8mm (.32 caliber) proved to be the practical upper limit and .270 the lower limit.
To get around the latter, Winchester introduced a line of Super Short Magnum (WSSM) cartridges in .22, .24, and .25 caliber based on a radically shortened version of their already short WSM case. These became the first of what I call the "non-magnum" magnums, designed to merely equal, rather than exceed, the performance of an existing standard cartridge. The .223 WSSM is the ballistic equal of the .220 Swift, the .243 WSSM is the ballistic equal of the 6mm Remington, and the .25 WSSM was designed to equal the .25-06 (debatable--in reality it's about like a .257 Roberts Improved).
Their tiny (but fat) rebated rim cases are only 1.670" long and the cartridge overall length is specified as 2.360". They simply lack the case capacity (not to mention a belt) to qualify as magnum cartridges of any sort. The fundamental meaning of magnum, remember, is "big case." The modern firearm press, in sharp contrast to the gun magazines of the 1960's that greeted the original .350 and 6.5mm short magnums with disdain, very conspicuously failed to point this out to their readers.
The reason for the travesty of the Winchester Super Short "Magnums," and for that matter the redundant WSM and SAUM cartridges, is simple: the word magnum sells rifles and ammunition. (And the popular gun magazines are too dependent on advertising from the major arms and ammo manufacturers to bite the hand that feeds them.) It's a matter of marketing, not performance. As we used to say about wanna-be hot rods in my flamed-out youth, "all show and no go."
Note: The rifle cartridges mentioned in this article are covered in detail in articles that can be found on the Rifle Cartridge Page.
Copyright 2005 by Chuck Hawks. All rights reserved.