The Short Magnum Cartridges
By Chuck Hawks
The first true commercial short magnum was the .350 Remington Magnum, introduced in 1965 by Remington. The 6.5mm Remington Magnum followed it the next year. These are short action calibers, designed to work through .308 Winchester length actions. They are both belted magnums based on a blown out .375 H&H case with a 25-degree shoulder, reduced to a length of 2.17 inches. Overall cartridge length is 2.8 inches.
Neither of Remington's original short magnums were commercial successes, although the .350 gained a sort of cult following. Factory loaded ammunition for the 6.5 and .350 Magnums was (temporarily) discontinued during the 1990's.
The .350 was reinstated in 2003 when Remington brought out the Model 673 bolt action rifle for the caliber. The Remington Custom Shop also chambers rifles for the .350 Magnum, which seems to have caught its second wind in the 21st Century. It was a cartridge decades ahead of its time when it was introduced.
The 6.5mm Rem. Mag. was reintroduced in 2004, also in the Model 673. It is worth noting that the 6.5mm Mag. handily out-performs the new .25 WSSM, also introduced in 2004, as a big game hunting cartridge.
Given the initial lack of consumer acceptance, the development of short magnums languished after 1966. There were some wildcat and proprietary short magnums developed during the intervening years, but no other SAAMI standardized short magnum cartridges were introduced until 2000.
That's when Winchester kicked over the traces and brought out their .300 WSM cartridge, based on a new bottleneck case with a head diameter of .555 inch and no belt. The WSM magnum case has a 35-degree shoulder, a length of 2.1 inches, and a very short neck. The overall cartridge length is 2.86 inches.
Meanwhile, Remington had made the first .300 Short Action Ultra Mag cases in 1999 and was already well along in the process of developing their Short Action Ultra Mag cartridges. These are based on the fat (.550 inch head diameter), beltless, .300 Ultra Mag case shortened to a length of 2.015 inches. The 30-degree shoulder angle of the parent case was retained, and the neck is very short. The overall cartridge length was set at 2.825 inches. This length was chosen to allow it to work in the Model 7 short action rifle. Remington introduced their .300 SAUM shortly after Winchester's .300 WSM hit the market.
The main argument in favor of any of the short magnums is their alleged greater efficiency due to their shorter powder column. The theory is that this shorter but wider powder column is more quickly and evenly ignited by the explosion of the primer, yielding more consistent pressure and somewhat improved accuracy compared to a standard length cartridge of the same capacity. More important, the short magnum cartridges work through short rifle actions, which saves about 1/2 inch of bolt throw as well as overall rifle length, and a few ounces of weight. (The latter is rather a mixed blessing when shooting a magnum cartridge.)
In reality, many factors influence intrinsic accuracy and performance more than the length of the powder column inside of the cartridge. Paramount are the uniformity and concentricity of the bullet, the quality and precision of the rifle barrel, the care taken in bedding the barrel and inletting the stock, and the care with which the loads are assembled and matched to the rifle. In a hunting rifle, any advantage conferred by a shorter powder column is insignificant.
All of the WSM and SAUM cartridges use a .532-.534 inch rebated rim of standard (.375 H&H) Magnum diameter. Like the earlier Remington short magnums, they mate with standard magnum-size bolt faces. However, their fat bodies have a head diameter immediately above the extractor groove of about .55 inch. The body of the case is bigger around than the rim. This miracle of design is called a rebated rim and it allows increased powder capacity compared to the earlier .350 Magnum case, at the price of decreased feed reliability and one cartridge less magazine capacity.
With any rebated rim case, the face of the bolt has less overlap with the rim of the case as it attempts to slide it forward and out of the magazine lips. This can lead to feeding failures and over-ride jams. For this reason, cartridges with rebated rims are not regarded as a good choice for use in rifles that might be used on dangerous game. Magazine capacity may be reduced by one cartridge because the WSM and SAUM cases are so fat--another reason standard magnum cartridges are preferred for use on dangerous game. (An unnecessary reduction in firepower is clearly undesirable when hunting dangerous game.) Nor are their sharp 30-35 degree shoulders conducive to smooth and reliable feeding. In fact, one of the justifications for the extremely sloping 8.5 degree shoulders of the original .375 and .300 H&H Magnum cartridges was feed reliability because of their anticipated use on dangerous game.
Following the initial success of the .300 WSM, the .270 WSM, 7mm WSM and 7mm SAUM were introduced. In 2005 the .325 WSM came along. While the .350 Rem. Mag. and 6.5mm Rem. Mag. are unique because of their short, belted cases (and easy to tell apart because one has a skinny bullet and one a fat bullet), the new WSM and SAUM short magnums all look very similar to each other. None, however, are interchangeable.
In 2003 Winchester introduced a line of Super Short Magnum (WSSM) cartridges, starting with the .223 WSSM and .243 WSSM. In 2004 they announced the .25 WSSM. All of these are based on the WSM case shortened to a length of only 1.65" and a COL of 2.36". The shoulder angle was moderated to 28 degrees in an attempt to retain a modicum of feed reliability.
The WSSM cartridges have caused major problems for rifle designers attempting to work with these very short, very fat cases, because they are an inherently poor design for use in the box magazines of almost all modern repeating rifles. The WSSM's are really best suited for use in single shot rifles, just like the bench rest cartridges that inspired them and they have been a sales flop. As far as I can tell, all WSSM caliber rifles have been discontinued, although Winchester continues to offer the ammo.
The most recent short magnum cartridges, as of this writing, are the .300 and .338 Ruger Compact Magnums (RCM). These .308 length offerings, developed by Hornady for Ruger, are based on shortened .375 Ruger case. This is a beltless bottleneck case with a rim and head diameter of .532". The RCM's were introduced in 2008.
Hornady offers .300 RCM factory loads with 150, 165 and 180 grain bullets; 200 and 225 grain bullets are offered in the .338 RCM. The performance of the .300 RCM is comparable to that of the other .300 short magnums, while the .338 RCM--a true medium bore cartridge--is comparable to the .350 Rem. Mag. and superior to the .325 WSM.
Note that these RCM cartridges are not rebated rim designs. This means that they offer improved feeding reliability compared to the WSM and SAUM short magnums. As such, they (along with the 6.5mm and .350 Rem. Mags.) are the best designed and most reliable of the short magnum cartridges. For 2017 they are available ONLY in the Ruger Guide Gun.
Let's take a look at the ballistics and prospects of the various short magnum cartridges, starting with the WSSM trio. These should have been named WSSC (Winchester Super Short Cartridge), for the WSSM cartridges are not magnum cartridges in any sense of the word and thus do not really merit inclusion in this article. The WSSM's are hard pressed to equal the performance of existing short action cartridges, such as the .220 Swift, 6mm Remington and .257 Roberts +P. Their performance is easily exceeded by standard cartridges, such as the .25-06. Compared to true magnum cartridges such as the .240 and .257 Weatherby Magnums they are an embarrassment. They have not achieved any lasting commercial success and WSSM rifles have already been discontinued.
The true short magnum cartridges begin with the 6.5mm Rem. Mag. The Remington 6.5mm Magnum factory load drives a 120 grain bullet to a muzzle velocity (MV) of 3210 fps and muzzle energy (ME) of 2745 ft. lbs., well beyond the performance of the standard short action .260 Remington. The Hornady Reloading Handbook lists loads up to 3000 fps with 140 grain bullets, and 2800 fps with their 160 grain bullet. All velocities were measured in a 24 inch rifle barrel. IMR 4350 seems to be an efficient powder for this cartridge.
The 6.5mm Remington Magnum is a flat shooting, long range CXP2 class game (deer, antelope, sheep, goat, and black bear) cartridge on the order of the .270 Winchester. It has plenty of killing power, even when fired from a 22 inch barrel. And it offers moderate recoil (13.1 ft. lbs. in an 8 pound rifle) in the light weight hunting rifles that are the natural home of short magnum cartridges.
The newer .270 Winchester Short Magnum cartridge has factory loads using a 130 grain bullet at a MV of 3275 fps and ME of 3096 ft. lbs., a 140 grain bullet at a MV of 3125 fps and ME of 3035 ft. lbs. and a 150 grain bullet at a MV of 3150 fps and ME of 3304 ft. lbs. These figures were all taken in a 24 inch test barrel.
The .270 WSM shoots as flat as the 6.5mm Magnum and hits a little harder. It is probably a better choice than the 6.5 Magnum for large CXP3 class game like elk. The .270 WSM kicks a lot harder than the 6.5mm Magnum, just under 19 ft. lbs. in an 8 pound rifle, but less than the other short magnum cartridges.
The 7mm WSM and 7mm Rem. SAUM boast similar ballistics, although neither has become popular. The following are Winchester 7mm WSM figures, with Remington 7mm SAUM figures in parenthesis. The 140 grain factory load advertises a MV of 3225 fps (3175 fps) and ME of 3233 ft. lbs. (3133 ft. lbs.). The 150 grain factory load advertises a MV of 3200 fps (3110 fps) and a ME of 3410 ft. lbs. (3221 ft. lbs.). The 160 grain factory load claims a MV of 2990 fps (2960 fps) and ME of 3176 ft. lbs. (3112 ft. lbs.). All figures taken in 24 inch test barrels.
The new 7mm short magnums are clearly redundant. They are too similar to each other and neither offers any ballistic advantage over the established and much more popular 7mm Remington Magnum. Unfortunately, their stubby, short necked cases are not well adapted to 160 and 175 grain bullets, so they are less suitable for hunting the large game for which most customers purchase a 7mm Magnum rifle. The standard length 7mm Rem. Mag. has about a 100 fps advantage with these heavier bullets. Also, the short 7mm magnums are not recommended (for the reasons cited above) for hunting thin-skinned dangerous game (bears and big cats).
The .300 WSM, .300 Rem. SAUM and .300 RCM also advertise similar ballistics. The following are Winchester .300 WSM figures. The 150 grain factory load has a claimed MV of 3300 fps and ME of 3628 ft. lbs. The 180 grain factory load claims a MV of 2970 fps and ME of 3526 ft. lbs. These figures were taken in 24 inch test barrels and WSM hunting rifles generally fall about 100 fps short.
Any .300 Magnum is most appropriate when the emphasis in on hunting the larger species of big game. With the exception of the .300 RCM, the other .300 Short Magnums are not recommended for use on dangerous game. The biggest problem with any .300 Magnum is its excessive recoil, which is well beyond the 15-20 ft. lb. limit the average shooter would do well to observe. Recoil energy with either of the .300 short magnums runs about 23-26 ft. lbs. in an 8 pound rifle, depending on bullet weight. The .300 WSM has found a place in the market, while the .300 SAUM is already obsolescent.
In the same class as the .300 short magnums is the .325 WSM. This cartridge came about as the result of a failed attempt to create a .338 WSM. The .325 WSM is intentionally misnamed to make it sound bigger than it is. It actually has a .315" bore diameter and should have been named the .315 WSM. It is an 8mm cartridge and its performance is nearly identical to that of the .300 WSM. The most important difference between this cartridge and the .300 WSM is the relative scarcity of 8mm bullets for reloading. Another drawback is its vicious recoil in the light Browning and Winchester rifles supplied in .325 WSM, recoil comparable to the .338 RCM and in excess of the .350 Rem. Mag.
The .338 RCM is offered factory loaded with 200 and 225 grain bullets, which is fine as far as it goes. It is an excellent elk cartridge. Unfortunately, the long 250 grain bullets that made the .338 Win. Magnum's reputation as a slayer of giant animals takes up too much powder space in the short RCM case to be practical. That leaves the .338 RCM a definite step ahead of the .325 WSM, but clearly inferior to the .338 Win. Mag.
The .350 Rem. Mag. is a true medium bore cartridge. The ballistics of the .350 Remington Magnum factory load introduced in 2003 claim a 200 grain bullet at a MV of 2775 fps and ME of 3419 ft. lbs. The discontinued Remington factory load drove a 250 grain bullet at a MV of 2419 fps with ME of 3220 ft. lbs. These figures are well beyond what the short action .358 Winchester can achieve.
Anyone shooting a .350 Magnum rifle today should be reloading. The Speer Reloading Manual No. 13 shows top velocities of 2942 fps with their 180 grain bullet, 2676 fps with their 220 grain bullet and 2484 fps with their 250 grain bullet, all taken in the 22 inch barrel of a Ruger M-77 rifle.
The .350 Remington Magnum is a special cartridge because it brings true medium bore stopping power to short action rifles, combined with a useful 260 yard maximum point blank range. As a cartridge for a "guide rifle" it is hard to beat. Recoil is right up there, at about 25 ft. lbs. in an 8.5 pound rifle, although this is actually moderate for a medium bore magnum. The .350 Rem. Mag. is a useful cartridge that remains my favorite short magnum.
The 6.5mm Rem. Magnum, .270 WSM and .350 Rem. Magnum are unique cartridges and each offers something special to the shooter. They are not just duplicates of earlier cartridges. These are the most useful of the short magnum cartridges, although not the most popular.
The .300 WSM seems to be the favorite among all of the short magnums. It pretty well fills the bill for a short action elk caliber with all-around capabilities and it was on the ground first, although the .300 RCM is technically superior. The .300 SAUM is already obsolescent, as even Remington has quit chambering rifles for it. As for the other short magnum calibers, time will tell, but they are not setting any sales records.
There has been speculation about what other calibers might be offered in one or the other of the short magnum formats. I can see some appeal to the idea of a .250 Short Magnum based on the .300 RCM case. This would exceed .25-06 performance in a short action cartridge and make an excellent, although specialized, long range plains and mountain rifle caliber. Such a cartridge would have no advantage over the .257 Weatherby and could not match that cartridge's ballistics, but it would clearly outperform the .25 WSSM. That alone might be a good reason for Ruger and Hornady to take such a step.
Interesting cartridges, these short magnums. Those who are interested can read the individual articles about the various short magnums on the Rifle Cartridge Page.
Copyright 2002, 2017 by Chuck Hawks. All rights reserved.