Compared: The .300 WSM and .300 Rem. SAUM
By Chuck Hawks
The introduction of a new generation of short action (.308 Winchester length) magnum hunting cartridges generated a lot of interest among shooters and in the shooting press. Winchester and Remington were simultaneously (and separately) developing their new .300 Short Magnum cartridges.
Winchester has introduced .270, 7mm, .300 and .325 (actually 8mm) Winchester Short Magnum (WSM) cartridges and Big Green has introduced the 7mm and .300 Remington Short Action Ultra Mags (SAUM). None of these cartridges are interchangeable, although all are based loosely on the old British .404 Jeffery case.
These are not the first short magnums, the .350 Remington Magnum and 6.5mm Remington Magnum of 1964-1965 hold that honor. Those cartridges were way ahead of their time. Nor are the WSM and SAUM calibers the last word in short magnums, as the subsequent introduction of the .300 and .338 Ruger Compact Magnum (RCM) cartridges shows.
For some 35 years after the mid-1960's introduction of the .350 Rem. Mag. and 6.5mm Rem Mag., the major ammunition companies introduced no other short magnum cartridges. Then, in 1999-2000, the dam broke and the WSM and Rem. SAUM cartridges began appearing. The .300 WSM and .300 Rem. SAUM are as alike in concept and capability as two peas in a pod. It seems very unlikely that both could prosper commercially and, while the .300 WSM has achieved at least a modest level of popularity, the .300 SAUM appears to be dying on the vine. One indication of this is that Remington is now offering rifles and ammunition in .300 WSM, while the reverse is not true.
.300 Remington Short Action Ultra Mag
The .300 Remington SAUM is based on a shortened version of their .300 Ultra Mag case, which was itself derived from the .404 Jeffery case. Chopping a case that big down to a length of 2.015" and a cartridge overall length (COL) of 2.825" produces a rather strange looking round, particularly since it has an unusual rebated rim (which means that the rim is smaller in diameter than the case body), and a sharp 30 degree shoulder. This shoulder profile, as bad as it is from the standpoint of reed reliability, is slightly better than that of the .300 WSM.
Remington wisely allowed for a case neck slightly over one bullet diameter long at 0.311" to adequately support the long bullets so often used in .300 Magnum cartridges. And the .300 Rem. SAUM is slightly more efficient than the .300 WSM, by which I mean that the same powder charge behind the same bullet will give slightly higher velocity in the Remington case. These are factors that may be important to some reloaders.
Because it is so fat, the .300 SAUM case has almost as much capacity as the standard length .300 Win. Mag. Because the short, fat design promotes a more efficient powder burn, the end result is velocities close or equal to those of .300 Winchester Magnum factory loads with bullets up to 180 grains in weight. (For the record, it is only fair to point out that, according to the fifth edition of the Nosler Reloading Guide, the .300 Win. Mag. can exceed the best velocities attainable in the .300 SAUM by about 150 fps with a 200 grain bullet.)
Remington factory loads for the .300 SAUM are available with 150, 165, and 180 grain bullets. The 150 grain bullet has a catalog muzzle velocity (MV) of 3200 fps and muzzle energy (ME) of 3410 ft. lbs. The 165 grain bullet has a catalog MV of 3075 fps and ME of 3464 ft. lbs. The 180 grain bullet has a catalog MV of 2960 fps and ME of 3501 ft. lbs.
All of those velocities were developed in 24" test barrels. In 22" rifle barrels there is considerable velocity loss (about 60 fps according to Remington estimates). For more in-depth information, please see my article "The .300 Remington SAUM" on the Rifle Cartridge Page.
.300 Winchester Short Magnum
Winchester stole a lead by getting their .300 WSM into rifles and the hands of shooters before Remington could introduce their .300 Rem. SAUM. Winchester/Olin (ammunition) and Winchester/USRAC + Browning (rifles) cooperated to make this happen.
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". Like the .300 SAUM, the .300 WSM has a rebated rim that will match up to a standard magnum diameter bolt face. The .300 WSM 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, shorter neck, slightly longer COL) gives the .300 WSM case slightly greater powder capacity than the .300 SAUM case.
For technical reasons fat, short, rebated rim cartridges with very sharp shoulders tend to have feeding problems from the box magazines typically found in bolt action rifles. This may be why Winchester offers the .300 WSM only in controlled round feed models of their Model 70 rifle. Browning A-Bolt II's, however, are push feed rifles and they are also available in .300 WSM caliber.
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.
Winchester wisely provides 24" barrels on all .300 WSM caliber rifles. Browning, however, has standardized the rather 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.
Here are the published velocity figures for the Remington and Winchester .300 Short Magnum factory loads. (Caliber, bullet weight and style - MV, velocity at 100 yards, velocity at 200 yards, velocity at 300 yards.)
Velocity is important because it flattens trajectory, making hitting easier at extended ranges, and is the most important factor in determining bullet energy. Velocity may also play a role in transmitting shock to the animal's system. These figures show that, while the two cartridges offer similar velocities with the popular 180 grain bullets, the .300 WSM has an advantage with 150 grain bullets. This amounts to a 100 fps advantage at the muzzle and slowly increases to a 260 fps advantage at 300 yards. This is the practical benefit from the .300 WSM's greater powder capacity. Most shooters, Winchester hopes, will not notice the subtle drawbacks incurred due to the sharper shoulder and shorter neck.
Note, however, that the very slight 10 fps advantage possessed by the 180 grain .300 WSM Fail Safe bullet at the muzzle is more than cancelled out down range by the superior ballistic coefficient (BC) of the Nosler Partition bullet used by Remington in the .300 SAUM. At 300 yards the SAUM's bullet is traveling 72 fps faster than the Winchester Fail Safe bullet.
Velocity and bullet weight are the factors used to compute kinetic energy, an objective measurement of a cartridge's power. Energy is an important factor in penetration and killing power. It's the "power" that makes it possible for the bullet to destroy tissue and effect a quick kill. Here are the published energy figures for the Remington SAUM and Winchester WSM factory loads. (Caliber, bullet weight and style - ME, energy at 100 yards, energy at 200 yards, energy at 300 yards.)
Of particular interest is the superiority of the .300 WSM with relatively light 150 grain bullets, which amount to some 431 ft. lbs. of remaining energy at 300 yards. And equally, its lack of superiority with the heavy 180 grain bullets that are the most useful weight in .300 Magnum cartridges. For hunting large CXP3 class game, the primary justification for the existence of any .300 Magnum caliber, there is little practical difference in energy between the .300 WSM and .300 SAUM.
Ballistic coefficient and sectional density
Since the .300 WSM and .300 SAUM can use bullets of the same weight, sectional density (SD), which is based on bullet weight and diameter, will be the same for both calibers with any given bullet weight. The SD of .30 caliber (.308" diameter) bullets are as follows: 150 grain, .226; 165 grain, .248; 180 grain, .271.
Ballistic coefficient (BC), which is basically a measure of a bullet's aerodynamic efficiency, depends on the shape of the bullet as well as its caliber and sectional density. The .300 WSM and .300 SAUM are not factory loaded with identical bullets, although they could be, so the BC of the bullets used by Remington is different from the BC of the bullets used by Winchester. Here are the BC figures for the bullets we have been comparing.
Velocity will ultimately be the primary determining factor regarding trajectory when comparing these two calibers. Ballistic coefficient will play a subsidiary role.
A flat trajectory is desirable because it extends the maximum point blank range (MPBR) of the rifle and makes accurate bullet placement easier. And bullet placement is the most important factor in killing power. The trajectories of the .300 WSM and .300 SAUM factory loads are shown below. The MPBR is calculated for a bullet path that rises no more than 3" above the line of sight and falls no more than 3" below the line of sight. (Caliber, bullet weight and type at MV: bullet path at 100 yards, bullet path at 200 yards, MPBR in yards.)
Higher velocity and higher ballistic coefficient both contribute to a flatter trajectory. With 150 grain factory loads the .300 WSM has the advantage in both, so it is no surprise that it offers a slightly flatter trajectory and 17 yards of MPBR.
In terms of trajectory the 165 grain PSP Core-Lokt bullet as factory loaded in the .300 SAUM is no bargain. The trajectory of the 180 grain Remington factory load is actually slightly flatter and the 180 grain bullet has a 2 yard advantage in MPBR over the 165 grain bullet.
The 180 grain bullets are the most popular in both calibers. Comparing the trajectories of the premium 180 grain bullets we see that their rise at 100 yards is identical. But the Remington load has 0.5" less drop at 300 yards and a 6 yard advantage in MPBR due to the higher BC of the 180 grain Partition bullet.
This is a difficult thing to compare because it is such a complex subject. Energy, penetration, frontal area, terminal performance, velocity, and ballistic coefficient all influence killing power. While no killing power formula is 100% accurate, the Optimum Game Weight (OGW) formula developed by Edward A. Matunas and published in the 47th edition of the Lyman Reloading Handbook does attempt to take into consideration all of the diverse factors involved. One positive sign is that the resulting OGW table usually matches the observations of experienced big game hunters.
The OGW formula shows the following results. (Cartridge, bullet weight - OGW in pounds at 100 yards, OGW in pounds at 200 yards, OGW in pounds at 300 yards.)
The superiority of the .300 WSM with 150 grain bullets is again apparent, as its higher velocity, energy, and BC results in greater killing power at all ranges. The 150 grain bullet in the .300 WSM is also superior to the 165 grain bullet in the .300 SAUM.
However, the 180 grain Partition bullet in the .300 SAUM delivers the top scores in optimum game weight. The superior BC of that bullet translates into greater downrange velocity and energy and consequently greater killing power. Remington chose their 180 grain premium bullet wisely, and it makes the .300 SAUM the deadliest of the two .300 short magnums when factory loads are compared.
Reloaders can make good use of the extra case capacity of the .300 WSM to drive the bullet of their choice (including the 180 grain Nosler Partition) to higher velocity than can be achieved in the .300 SAUM. However, it should be remembered that the longer neck of the .300 SAUM case is an advantage and that this is especially true when using spitzer bullets weighing 180 grains or more.
The final point to consider is recoil. The more a rifle kicks, the harder it is to place a bullet perfectly. And bullet placement is (by far) the most important factor in killing power.
There is actually little difference in recoil between the .300 WSM and .300 SAUM in rifles of the same weight, as one can see from the table that follows. Recoil is calculated for rifles weighing 8.25 pounds, about the weight of a scoped Remington Model Seven Magnum or Winchester Model 70 Classic Stainless rifle. (Caliber, bullet weight in grains at MV, rifle weight - free recoil energy in foot pounds.)
What advantage there is in recoil belongs to the .300 SAUM, which kicks slightly less than the .300 WSM with all bullet weights. However, both .300 short magnums give the shooter something to think about before he or she pulls the trigger.
There can be no doubt that these two cartridges are quite similar in design, capability and purpose. Practically speaking, the choice will probably come down to the buyer's preference in rifles. If it is for a Remington rifle, then either cartridge is available. If it is for a Browning or Winchester rifle, then it will be .300 WSM because they do not chamber for the .300 Rem. SAUM.
Only if buying a third brand of rifle that is chambered for both cartridges, or if the buyer regards, say, Remington and Winchester rifles equally desirable will the cartridge itself likely become the deciding factor. Then the customer will have to decide whether the slightly greater case capacity and somewhat higher performance of the WSM cartridge with maximum loads outweighs the slightly more "friendly" design of the Remington SAUM case (a hair less recoil, longer neck, 5 degrees less shoulder angle and slightly greater efficiency).
The .300 WSM's most obvious performance advantage is when using relatively light (for a .300 Magnum) 150 grain bullets. This suggests that the .300 WSM might be a somewhat better choice if the primary mission is long range shooting of light framed CXP2 class game.
Comparing factory loads makes it clear that the .300 SAUM gives away nothing with the heavy 180 grain bullets most suitable for taking large CXP3 class game. Its longer neck and very slightly lower recoil suggest that it may be the cartridge to choose if the primary intention is to hunt large game with factory loads. It is probably a marginally superior cartridge for reloaders. Due to their case design, neither cartridge is a good choice for use on potentially dangerous game, but in that context the 30 degree shoulder of the SAUM is slightly better than the 35 degree shoulder of the WSM. There are valid technical reasons for choosing the .300 Rem. SAUM if one is so inclined.
The .300 WSM has gained the advantage in the marketplace because it was first on the ground and its slightly higher velocity and energy are easily quantifiable, while the .300 Remington SAUM's advantages are more intangible. Also, Winchester did a far better job of promoting their new cartridges than Remington. It is likely that, in the future, .300 WSM rifles and ammunition will be more widely available than .300 Rem. SAUM rifles and ammunition.
Copyright 2003, 2012 by Chuck Hawks. All rights reserved.