Remington Ultra Magnum, or RUM, refers to a "family" of cartridges developed between 1999 and 2002 by Remington Arms. All of the RUM cartridges are based on the ''

.404 Jeffery The .404 Jeffery is a rifle cartridge designed for hunting large, dangerous game animals, such as the " Big Five" (elephant, rhino, cape buffalo, lion and leopard) of Africa. The cartridge is standardized by the C.I.P. and is also known as .404 ...

'' non-belted magnum cartridge. There is a long-case line, as well as a shortened version designed to fit a short rifle action (such as a

.308 Winchester The .308 Winchester is a smokeless powder rimless bottlenecked rifle cartridge widely used for hunting, target shooting, police, military, and personal protection applications globally. It is similar but not identical to the 7.62×51mm NATO ...

). The long case is very large and provides performance that exceeds existing commercial magnums, such as the

.300 Winchester Magnum The .300 Winchester Magnum (also known as .300 Win Mag or .300 WM) (7.62×67mmB, 7.62x66BR) is a belted, bottlenecked magnum rifle cartridge that was introduced by the Winchester Repeating Arms Company in 1963. The .300 Winchester Magnum is a m ...

and

.300 Weatherby Magnum The .300 Weatherby Magnum is a .30 caliber rifle cartridge created by Roy Weatherby in 1944 and produced by Weatherby. It has become the most popular of all the Weatherby cartridges. Background Roy Weatherby already had experience with oth ...

. The short design is the same idea as used in the

Winchester Short Magnum Winchester Short Magnum, or WSM, refers to a family of rebated rim bottlenecked centerfire short magnum cartridges developed in the early 2000s by the U.S. Repeating Arms Company, the maker of Winchester rifles and one of the oldest firearms man ...

cartridges. The shorter cartridges are known as Remington Short Action Ultra Magnum, RSAUM, RSUM, or SAUM. The RUM family of cartridges are

Delta L problem The delta L problem (ΔL problem) refers to certain firearm chambers and the incompatibility of some ammunition made for that chamber. ΔL is a Commission Internationale Permanente (C.I.P.) geometric dimensioning and tolerancing definition for c ...

cartridges, meaning they can present unexpected chambering and/or feeding problems. The

article explains this problem in more detail.

Influences

7.21 Lazzeroni

The RUM family is based on work done creating short magnums by John Lazzeroni, similar to the

line. Lazzeroni's short magnums ( 7.21 Lazzeroni Tomahawk) were designed to operate in a short-action rifle, instead of requiring a long action. The U.S. Repeating Arms Company was the first major manufacturer to commercialize Lazzeroni's concept, followed shortly thereafter by

Remington Remington may refer to: Organizations * Remington Arms, American firearms manufacturer * Remington Rand, American computer manufacturer * Remington Products, American manufacturer of shavers and haircare products * Remington College, American c ...

with their "Short Action Ultra Mag" line.

6 mm Benchrest

Another influence was a series of 6 mm cartridges developed for bench-rest target shooting competitions in the 1970s. The idea behind these cartridges was that a short, fat cartridge would be more "efficient" than the traditional long, narrow cartridge, as more of the powder column would be in the immediate vicinity of the primer as it detonated. In turn, this would mean that a cartridge of this type would be able to propel a bullet at speeds comparable to those of "magnum" cartridges of the same caliber using significantly less powder.

RUM cartridges

The cartridges in this family are: *

7mm Remington Ultra Magnum The 7mm Remington Ultra Magnum or 7mm RUM is a 7mm rifle cartridge introduced by Remington Arms in 2001. Overview The 7mm RUM was created using the .404 Jeffery case which was also used to develop the .375 RUM .300 RUM, and .338 RUM . By ne ...

.300 Remington Ultra Magnum The .300 Remington Ultra Magnum, also known as the .300 Ultra Mag, 7.62×72mm or .300 RUM is a 7.62 mm (.308 inch) rifle cartridge introduced by Remington Arms in 1999. The .300 Remington Ultra Magnum is one of the largest commercially ava ...

also known as the .300 Ultra Mag or .300 RUM *

.338 Remington Ultra Magnum The .338 Remington Ultra Magnum is a .338 caliber rifle cartridge introduced by Remington Arms in 2002. Design It is a beltless, rebated rim cartridge based on the .300 Remington Ultra Magnum case shortened .090" and necked-up to accept a 0.338 ...

.375 Remington Ultra Magnum The .375 Remington Ultra Magnum, also known as the .375 RUM is a .375 rifle Cartridge (firearms), cartridge introduced by Remington Arms in 2000. The cartridge is intended for large and dangerous game. It is a beltless, rebated rim cartridge c ...

SAUM cartridges

7mm Remington Short Action Ultra Magnum Remington introduced the 7mm Short Action Ultra Magnum (SAUM) cartridge in 2002 to compete with the 7mm Winchester Short Magnum cartridge. It was designed specifically for the Remington Model Seven Magnum rifle, and intended primarily for long ...

* .300 Remington Short Action Ultra Magnum

References