The .300 Remington Short Action Ultra Mag
By Chuck Hawks
The new short action .300 magnums are powerful, compact cartridges. They are suitable for game from the size of deer and antelope to the largest thin-skinned game worldwide.
The ability to achieve a comparatively flat trajectory with bullets of 200 grains and heavier, suitable for very large game, is the biggest advantage the standard length .300 Magnums have over high intensity cartridges like the .30-06. Unfortunately, this attribute is compromised in the new very short magnums such as the .300 Rem. SAUM--a point to ponder if you are shopping for a .300 Magnum rifle.
The main drawback to the .300 Short Magnums is recoil, particularly in the lightweight rifles offered by many manufacturers. Excessive recoil often leads to flinching, which causes inaccurate and erratic shooting.
A 7.25 pound Model Seven rifle chambered for the .300 Rem. SAUM rocks the shooter with about 26.8 ft. lbs. of recoil energy. Tests have shown that the average shooter can't withstand over 20 ft. lbs. of recoil, and many shooters can't tolerate over about 15 ft. lbs. without developing a flinch. The .300 Short Action Ultra Mag is way over the limit and a wise shooter will take it in very small doses.
Winchester and Remington both introduced short action .300 beltless magnums in 2001. Winchester's .300 WSM was announced during the first part of 2001, followed by Remington's announcement of the similar .300 Remington Short Action Ultra Magnum (SAUM) in the second half of 2001.
The .300 SAUM is based on radically shortened version of the Remington .300 Ultra Mag case. Like the full length Ultra Mag cartridges, the .300 SAUM is a beltless bottleneck case with a rebated rim (a rim smaller in diameter than the case body). The rim diameter is .534", which allows the cartridge to mate with standard diameter magnum bolt faces. The base of the case measures .550", and the body tapers slightly to a diameter of .535" at the beginning of the 30 degree shoulder. The case length is 2.015" and the overall cartridge length is 2.825". The SAAMI maximum average pressure is reported to be 52,000 cup.
This short, extremely fat case has slightly less powder capacity than the standard length .300 Winchester Magnum. However, its performance with bullets of 180 grains or less is essentially identical to that of the established .300 Win. Mag. because its short case burns powder slightly more efficiently than the longer case.
Remington says that the SAUM cartridges' short overall length of 2.825" (the .308 Winchester is 2.810") allows shorter and lighter .300 Magnum rifles to be built. Remington introduced the .300 Rem. SAUM in their 7.25 pound Model 7 rifle, which has a 22" barrel. It is also offered in their 7.5 pound Model 673 Guide Rifle that also has a 22" barrel, and the Model 700 BDL SS, which comes with a 24" barrel. Ruger and Savage are also chambering rifles for the .300 SAUM cartridge.
Unfortunately, all .300 Magnums require a long barrel (26" is standard, and 24" is the minimum length) to burn the amount of powder necessary to achieve their superior ballistics. Cut a .300 barrel to 22" and you are just about as well off with a .30-06. Another problem is that standard size .300 Mag. rifles kick plenty hard already, and a light .300 generates recoil that is unacceptable to most shooters.
The .300 Rem. SAUM advertises ballistics virtually identical to the popular .300 Win. Mag. with 150 and 180 grain bullets (when fired in a 24" barrel). Heavier bullets protrude so far into the powder space of the stubby case that velocity is reduced compared to the standard length magnums. This limits the 300 SAUM's versatility, particularly for use on very large or dangerous game. In addition, the new .300 SAUM cartridge is so fat that magazine capacity is reduced by one round. The question of potential feeding problems with such a short, fat, sharp shouldered case with a rebated rim (negative properties in terms of feed reliability) has also been raised. Certainly the basic design of the .300 Rem. SAUM suggests that it is not intended for use on dangerous game.
Remington offers factory loads with three bullet weights (150, 165 and 180 grains) for the .300 SAUM. It should be noted that the velocities for all of them are quoted in a 24" test barrel, not the 22" barrels with which Remington Model Seven and Model 673 rifles are actually supplied.
With a 150 grain Pointed Soft Point (PSP) Core-Lokt Ultra bullet Remington claims a muzzle velocity (MV) of 3200 fps and muzzle energy (ME) of 3410 ft. lbs. The 200 yard figures are 2622 fps and 2290 ft. lbs.
With a 165 grain PSP Core-Lokt bullet Remington claims a MV of 3075 fps and ME of 3464 ft. lbs. The 200 yard figures are 2527 fps and 2339 ft. lbs.
For the popular 180 grain Nosler Partition bullet Remington claims a muzzle velocity of 2960 fps with 3501 ft. lbs. of muzzle energy. The 200 yard figures are 2571 fps and 2642 ft. lbs.
The trajectory of the .300 Rem. SAUM with a 165 grain bullet (BC .410) at a MV of 3075 fps looks like this: +2.5" at 100 yards, +3" at 145 yards, +2.3" at 200 yards, and -3" at 300 yards. This is very similar to the trajectory of the .300 Win. Mag. (and also the .300 WSM) with the same weight bullet.
Velocity loss in a 22" barrel is considerable. Chronograph results I saw showed that the 180 grain Remington .300 SAUM factory loads delivered about 100 fps less muzzle velocity than claimed when tested in the Model 7 Magnum's 22" barrel.
The fifth edition of the Nosler Reloading Guide shows that in the .300 Rem. SAUM their 180 grain bullets can be driven to a MV of 2712 fps by 58.5 grains of IMR 4350 powder, and 2952 fps by 62.5 grains of IMR 4350. These loads used Remington brass and primers, and velocity was measured in a 24" barrel.
The .300 Rem. SAUM has generated a lot of interest among shooters. Near the end of 2001 Remington announcing a 7mm Rem. SAUM based on a necked down .300 SAUM case.
I have tried to point out the bad as well as the good points of the .300 SAUM because most of the firearms press, in their excitement to promote something new, has not been inclined to report the full truth about the new cartridge. The drawbacks are something that shooters should understand before purchasing any light weight, short barreled .300 Magnum rifle.
It has been my hope that the interest generated by the introduction of the .300 SAUM, its offspring, and its competition would spur Remington to revive two earlier short magnum cartridges, the belted 6.5mm and .350 Remington Magnums. I was therefore pleased when, in 2003, Remington announced the reintroduction of the .350 Magnum in the Model 673 rifle. Perhaps the development of the .300 SAUM marks the dawning of the day of the true short magnum cartridge.
Copyright 2003, 2012 by Chuck Hawks. All rights reserved.