Script error
.300 Remington Ultra Magnum
.300 RUM cartridge
Type Rifle
Place of origin Canada
Service history
Wars War in Afghanistan,
Iraq War
Production history
Designer Remington
Designed 1999
Parent case .404 Jeffery
Case type Rimless, bottleneck
Bullet diameter .308 in (Bad rounding hereScript error mm)
Neck diameter .344 in (Bad rounding hereScript error mm)
Shoulder diameter .525 in (Bad rounding hereScript error mm)
Base diameter .550 in (Bad rounding hereScript error mm)
Rim diameter .534 in (Bad rounding hereScript error mm)
Case length 2.850 in (Bad rounding hereScript error mm)
Overall length 3.600 in (Bad rounding hereScript error mm)
Case capacity 110.2 gr H2O (7.163 cm³)
Rifling twist 1–10"
Primer type Large rifle magnum
Maximum pressure 65,000 psi (Bad rounding hereScript error MPa)
Ballistic performance
Bullet weight/type Velocity Energy
150 gr (Bad rounding hereScript error g) X3,456 ft/s (Bad rounding hereScript error m/s)3,979 ft·lbf (Bad rounding hereScript error J)
168 gr (Bad rounding hereScript error g) BTHP3,326 ft/s (Bad rounding hereScript error m/s)4,128 ft·lbf (Bad rounding hereScript error J)
180 gr (Bad rounding hereScript error g) BTSP3,256 ft/s (Bad rounding hereScript error m/s)4,238 ft·lbf (Bad rounding hereScript error J)
200 gr (Bad rounding hereScript error g) SP3,119 ft/s (Bad rounding hereScript error m/s)4,321 ft·lbf (Bad rounding hereScript error J)
220 gr (Bad rounding hereScript error g) RN2,970 ft/s (Bad rounding hereScript error m/s)4,310 ft·lbf (Bad rounding hereScript error J)
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 & HistoryEdit

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 & SpecificationEdit

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.

.300 Remington Ultra Magnum SAAMI cartridge dimensions – all dimensions in inches (mm)
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 (Bad rounding hereScript error mm). The barrel is to have a groove width of .115 in (Bad rounding hereScript error mm). Bore is given as .300 in (Bad rounding hereScript error mm) and a groove is .308 in (Bad rounding hereScript error 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 (Bad rounding hereScript error bar).

Remington’s ultra magnum cases were made wider than the .404 Jeffery case by .006 in (Bad rounding hereScript error 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 (Bad rounding hereScript error psi).


File:308 30-06 300WBY 300RUM.jpg

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 (Bad rounding hereScript error g) at 3,450 ft/s (Bad rounding hereScript error m/s), the 180 gr (Bad rounding hereScript error g) at 3,250 ft/s (Bad rounding hereScript error m/s) and the 200 gr (Bad rounding hereScript error g) at 3,032 ft/s (Bad rounding hereScript error 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 (Bad rounding hereScript error m) 200-yard (Bad rounding hereScript error m) 300-yard (Bad rounding hereScript error m) 400-yard (Bad rounding hereScript error m) 500-yard (Bad rounding hereScript error m)
Premier Scirocco Bonded 150 grains (Bad rounding hereScript error g) PR300UM5[3] Velocity 3,450 ft/s (Bad rounding hereScript error m/s) 3,211 ft/s (Bad rounding hereScript error m/s) 2,985 ft/s (Bad rounding hereScript error m/s) 2,769 ft/s (Bad rounding hereScript error m/s) 2,564 ft/s (Bad rounding hereScript error m/s) 2,369 ft/s (Bad rounding hereScript error m/s)
Energy 3,964 ft·lbf (Bad rounding hereScript error J) 3,434 ft·lbf (Bad rounding hereScript error J) 2,967 ft·lbf (Bad rounding hereScript error J) 2,554 ft·lbf (Bad rounding hereScript error J) 2,190 ft·lbf (Bad rounding hereScript error J) 1,869 ft·lbf (Bad rounding hereScript error J)
Bullet Drop −1.5 in (Bad rounding hereScript error cm) 2.6 in (Bad rounding hereScript error cm) 3.2 in (Bad rounding hereScript error cm) 0 in (0 cm) −7.8 in (Bad rounding hereScript error cm) −20.9 in (Bad rounding hereScript error cm)
Premier Scirocco Bonded 180 grains (Bad rounding hereScript error g) PR300UM3[3] Velocity 3,250 ft/s (Bad rounding hereScript error m/s) 3,051 ft/s (Bad rounding hereScript error m/s) 2,860 ft/s (Bad rounding hereScript error m/s) 2,677 ft/s (Bad rounding hereScript error m/s) 2,502 ft/s (Bad rounding hereScript error m/s) 2,334 ft/s (Bad rounding hereScript error m/s)
Energy 4,221 ft·lbf (Bad rounding hereScript error J) 3,719 ft·lbf (Bad rounding hereScript error J) 3,268 ft·lbf (Bad rounding hereScript error J) 2,864 ft·lbf (Bad rounding hereScript error J) 2,501 ft·lbf (Bad rounding hereScript error J) 2,177 ft·lbf (Bad rounding hereScript error J)
Bullet Drop −1.5 in (Bad rounding hereScript error cm) 2.9 in (Bad rounding hereScript error cm) 3.6 in (Bad rounding hereScript error cm) 0 in (0 cm) −8.5 in (−22 cm) −22.5 in (Bad rounding hereScript error cm)
Premier A-Frame 200 grains (Bad rounding hereScript error g) RS300UM2[3] Velocity 3,032 ft/s (Bad rounding hereScript error m/s) 2,793 ft/s (Bad rounding hereScript error m/s) 2,566 ft/s (Bad rounding hereScript error m/s) 2,352 ft/s (Bad rounding hereScript error m/s) 2,148 ft/s (Bad rounding hereScript error m/s) 1,954 ft/s (Bad rounding hereScript error m/s)
Energy 4,082 ft·lbf (Bad rounding hereScript error J) 3,464 ft·lbf (Bad rounding hereScript error J) 2,924 ft·lbf (Bad rounding hereScript error J) 2,456 ft·lbf (Bad rounding hereScript error J) 2,049 ft·lbf (Bad rounding hereScript error J) 1,695 ft·lbf (Bad rounding hereScript error J)
Bullet Drop −1.5 in (Bad rounding hereScript error cm) 3.7 in (Bad rounding hereScript error cm) 4.5 in (Bad rounding hereScript error cm) 0 in (0 cm) −10.8 in (Bad rounding hereScript error cm) −29.2 in (Bad rounding hereScript error cm)
Rifle sighted in 1.5 inch (2.5 cm) above bore axis. Altitude 1000 ft. Temperature 59 °F (Bad rounding hereScript error °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 (Expression error: Unrecognised punctuation character "[".Expression error: Unrecognised punctuation character "[".Expression error: Unrecognised punctuation character "[". Expression error: Unrecognised punctuation character "[".) 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 UsageEdit

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 (Bad rounding hereScript error m) for deer sized game and capable of taking elk sized game out to 700 yd (Bad rounding hereScript error 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 alsoEdit


  1. .300 RUM data at Accurate Powder
  2. Script error
  3. 3.0 3.1 3.2 Script error

Script error

Ad blocker interference detected!

Wikia is a free-to-use site that makes money from advertising. We have a modified experience for viewers using ad blockers

Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.