.300 Remington Ultra Magnum

.300 Remington Ultra Magnum

.300 Remington Ultra Magnum
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.300 RUM cartridge
Type Rifle
Place of originCanada
Production history
ManufacturerRemington Arms Company
Produced1999 - present
Parent case.404 Jeffery
Case typeRimless, bottleneck
Bullet diameterTemplate:Infobox firearm cartridge/convert
Neck diameterTemplate:Infobox firearm cartridge/convert
Shoulder diameterTemplate:Infobox firearm cartridge/convert
Base diameterTemplate:Infobox firearm cartridge/convert
Rim diameterTemplate:Infobox firearm cartridge/convert
Rim thicknessTemplate:Infobox firearm cartridge/convert
Case lengthTemplate:Infobox firearm cartridge/convert
Overall lengthTemplate:Infobox firearm cartridge/convert
Case capacityTemplate:Infobox firearm cartridge/convert
Rifling twist1–10"
Primer typeLarge rifle magnum
Maximum pressureTemplate:Infobox firearm cartridge/convert
Template:Infobox firearm cartridge/ballistics header Template:Infobox firearm cartridge/ballisticsTemplate:Infobox firearm cartridge/ballisticsTemplate:Infobox firearm cartridge/ballisticsTemplate:Infobox firearm cartridge/ballisticsTemplate:Infobox firearm cartridge/ballistics
Test barrel length: 24" (610 mm)
Source(s): Accurate Powder[1]

The .300 Remington Ultra Magnum, also known as the .300 Ultra Mag' or .300 RUM is a 7.62 mm (.300in.) caliber rifle cartridge, 7.62x72mm, or .30 caliber rifle cartridge introduced by Remington Arms in 1999. The .300 Remington Ultra Magnum is one of the largest commercially available .30 caliber magnums currently being produced. It is a beltless, rebated rim cartridge, capable of handling all large North American game, as well as long-range shooting. Among commercially produced .30-caliber rifle chamberings, the .300 Remington Ultra Magnum is second to the .30-378 Weatherby Magnum in cartridge-case capacity.

Origin & History

In the early 1980s Aubrey White and Noburo Uno of North American Shooting Systems (NASS) based in British Columbia Canada began experimenting with the full length .404 Jeffery by reducing the taper and necking it down to various calibers such as 7 mm, .308, 311, 338, 9.3 mm and .375. These cartridges were known variously as the Canadian Magnum or the Imperial Magnums. Rifles were built on Remington Model 700 Long Actions and used McMillan stocks. Cartridges were fire formed from .404 Jeffery cases with the rim turned down, taper reduced and featured sharp shoulders.

Both Remington and Dakota Arms purchased the formed brass designed by Noburo Uno for use in their own experimentation and cartridge development. In 1999 Remington released the first of a series of cartridges virtually identical to the Canadian Magnum cartridges which featured a slightly wider body, increased taper, and shallower shoulders and named it the .300 Remington Ultra Magnum. Dakota too released their own version of the cartridge but chose not to turn down the rim and shortened the case to work in a standard length action. Remington would go on to design their own shortened versions of the Ultra Magnum cartridge which they were to call the Remington Short Action Ultra Magnum or RSAUM for short.

Design & Specification

The .300 Remington Ultra Magnum is a member of the Remington Ultra Magnum cartridge family based on the .404 Jeffery via the Canadian Magnum cartridges. As these cartridges feature wider bodies than the belted magnums based on the .375 H&H case, these cartridges have greater case capacities than their corresponding full length belted Magnum cartridges such as the 7 mm Shooting Times Westerner, the .300 Weatherby Magnum, .340 Weatherby Magnum and the .375 Ackley Improved.

The .300 RUM features a rebated rim much like the .300 Canadian Magnum so as to allow the cartridge to function in the Remington M700 action without having to increase the bolt and bolt face diameter of the action. The down side is this may result in feeding failures and over-ride jams as the cartridge is cycled into the chamber and is considered undesirable in a dangerous game cartridge.[2] Unlike the belted Magnum cases based on the .375 H&H Magnum cartridge, the .300 RUM does not have a belt. All things being equal, a beltless cartridge would feed more reliably and more smoothly than a belted cartridge. Furthermore, as this is a beltless cartridge headspacing is designed to take place on the shoulder, which is considered beneficial by some as it is thought to promote accuracy and prolong case life of the cartridge.

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SAAMI compliant .300 Remington Ultra Magnum cartridge schematic: All dimensions in inches [millimeters].

SAAMI recommends that the barrel have a 6 groove contour with a twist rate of one revolution in 10 in (250 mm). The barrel is to have a groove width of .115 in (2.9 mm). Bore is given as .300 in (7.6 mm) and a groove is .308 in (7.8 mm). Maximum case overflow capacity is 122.5 gr. of water (7.30 cm3). SAAMI recommended Maximum Average Pressure is set at 65,000 psi (4,500 bar).

Remington’s ultra magnum cases were made wider than the .404 Jeffery case by .006 in (0.15 mm). The brass was made thicker so as to withstand the higher pressure of the new cartridge as the Jeffery cartridge had a maximum average pressure rating of 3,650 bar (52,900 psi).


Remington ammunition for the .300 RUM is available in three Power Levels. Power Level I duplicates the .30-06 Springfield, Power Level II that of the .300 Winchester and Power Level III is the full power load. Remington offers the full power (Power Level III) .300 Remington Ultra Magnum ammunition in 150 gr (9.7 g) at 3,450 ft/s (1,050 m/s), the 180 gr (12 g) at 3,250 ft/s (990 m/s) and the 200 gr (13 g) at 3,032 ft/s (924 m/s). These are among the highest velocities attained by a .30 caliber production rifle cartridge.

Performance Characteristics .300 Remington Ultra Magnum Power Level III Ammunition
Cartridge Criteria Muzzle 100-yard (91 m) 200-yard (180 m) 300-yard (270 m) 400-yard (370 m) 500-yard (460 m)
Premier Scirocco Bonded 150 grains (9.7 g) PR300UM5[3] Velocity 3,450 ft/s (1,050 m/s) 3,211 ft/s (979 m/s) 2,985 ft/s (910 m/s) 2,769 ft/s (844 m/s) 2,564 ft/s (782 m/s) 2,369 ft/s (722 m/s)
Energy 3,964 ft·lbf (5,374 J) 3,434 ft·lbf (4,656 J) 2,967 ft·lbf (4,023 J) 2,554 ft·lbf (3,463 J) 2,190 ft·lbf (2,970 J) 1,869 ft·lbf (2,534 J)
Bullet Drop −1.5 in (−3.8 cm) 2.6 in (6.6 cm) 3.2 in (8.1 cm) 0 in (0 cm) −7.8 in (−20 cm) −20.9 in (−53 cm)
Premier Scirocco Bonded 180 grains (12 g) PR300UM3[3] Velocity 3,250 ft/s (990 m/s) 3,051 ft/s (930 m/s) 2,860 ft/s (870 m/s) 2,677 ft/s (816 m/s) 2,502 ft/s (763 m/s) 2,334 ft/s (711 m/s)
Energy 4,221 ft·lbf (5,723 J) 3,719 ft·lbf (5,042 J) 3,268 ft·lbf (4,431 J) 2,864 ft·lbf (3,883 J) 2,501 ft·lbf (3,391 J) 2,177 ft·lbf (2,952 J)
Bullet Drop −1.5 in (−3.8 cm) 2.9 in (7.4 cm) 3.6 in (9.1 cm) 0 in (0 cm) −8.5 in (−22 cm) −22.5 in (−57 cm)
Premier A-Frame 200 grains (13 g) RS300UM2[3] Velocity 3,032 ft/s (924 m/s) 2,793 ft/s (851 m/s) 2,566 ft/s (782 m/s) 2,352 ft/s (717 m/s) 2,148 ft/s (655 m/s) 1,954 ft/s (596 m/s)
Energy 4,082 ft·lbf (5,534 J) 3,464 ft·lbf (4,697 J) 2,924 ft·lbf (3,964 J) 2,456 ft·lbf (3,330 J) 2,049 ft·lbf (2,778 J) 1,695 ft·lbf (2,298 J)
Bullet Drop −1.5 in (−3.8 cm) 3.7 in (9.4 cm) 4.5 in (11 cm) 0 in (0 cm) −10.8 in (−27 cm) −29.2 in (−74 cm)
Rifle sighted in 1.5 inch (2.5 cm) above bore axis. Altitude 1000 ft. Temperature 59 °F (15 °C). Values courtesy of Big Game Info Ballistic Calculator

The .300 RUM is an excellent long range cartridge with the ability to deliver a useful level of energy downrange especially with the power level III ammunition.. Due to its high velocity it exhibits less bullet drop than most other .30 caliber (7.62 mm) cartridges.

Compared to other production .30 caliber (7.62 mm) cartridges, only the .30-378 Weatherby Magnum surpasses the .300 Remington Ultra Magnum. Factory loaded .30-378 Weatherby Magnum ammunition has a 150–200 ft/s (46–61 m/s) velocity advantage over the .300 RUM cartridge with any given bullet weight. However, the .30-378 Weatherby Magnum is considered the most overbore production sporting cartridge available and is not considered as efficient as the .300 RUM cartridge. In part due to its excessive freebore lengths the claimed velocities by Weatherby is a resultant factor of this freebore length. If chambered to allow bullets to seat the lands of the rifling the large Weatherby cartridges would exhibit overpressure signs immediately. All things equal the .300 RUM and .30-378 Weatherby if chambered with the same throat and freebore would be comparable. Known freebore lengths of older Weatherby rifles have been in excess of 1 inch. The .30-378 is one of the most extreme cases of overbore and has among the highest throat erosion levels of any rifles.

Sporting Usage

The .300 Remington Ultra Magnum cartridge was conceived as a long range hunting cartridge and in this it excels over most other cartridges. It is able to launch bullets of good weights and sectional densities at high velocities and remaining energy to take game cleanly at longer ranges than lesser cartridges such as the .30-06 Springfield and even the .300 Winchester Magnum.

It is an excellent one gun cartridge for hunting all North American game species, though the cartridge is considered to be overly powerful for smaller big game species such as pronghorns, white-tail and mule deer. The cartridge comes into its own for larger deer species such as elk and moose. The .300 RUM is considered an excellent cross canyon rifle when hunting in the foothills or the Rockies where the opportunity for long distance shooting can present itself. The cartridge has enough remaining energy at 875 yd (800 m) for deer sized game and capable of taking elk sized game out to 700 yd (640 m).

Due to the excess power and energy which the cartridge can bring to bear and the very flat shooting capability of the cartridge, the .300 RUM makes a first-rate choice when hunting African plains game, especially in the Serengeti. With the exception of dangerous game the cartridge would be a good candidate for an all round rifle cartridge for African game species.

See also


Template:Remington Cartridges Firearms