About 338 Rem Ultra Mag
The .338 Remington Ultra Magnum (RUM) is a high-powered, long-range rifle cartridge introduced by Remington in 2002.
It was developed by necking up the .300 Remington Ultra Magnum case to .338 caliber, offering a hard-hitting round designed to compete with other large-caliber, high-velocity cartridges like the .338 Lapua Magnum.
Known for its flat trajectory and exceptional energy retention, the .338 RUM is widely used for big game hunting, making it an excellent choice for hunters pursuing elk, moose, and other large North American game at extended distances.
Additionally, its ballistic performance makes it a capable option for long-range precision shooting, though it is less common in military and tactical applications compared to the .338 Lapua.
Popular .338 Rem Ultra Mag Brands
While the .338 RUM is favored for its raw power and accuracy, it also comes with significant recoil and limited commercial availability, making it a niche choice for experienced shooters looking for extreme performance in the field.
Several manufacturers produce high-quality .338 RUM ammunition, including:
Remington is one of the oldest and most recognizable names in the American shooting-sports industry. Eliphalet Remington founded the company in 1816, while dedicated metallic centerfire ammunition production dates to the establishment of Remington Ammunition Works in 1871. Today, Remington ammunition is manufactured in Lonoke, Arkansas.
The brand's major strength is breadth and familiarity. Rather than concentrating exclusively on premium or specialized ammunition, Remington serves a large cross-section of the sporting market, including rifle, handgun, rimfire and shotgun ammunition. Its long history also gives it unusually strong brand recognition among American hunters and recreational shooters.
Remington is particularly associated with traditional hunting and sporting ammunition and represents more of a heritage, mainstream ammunition brand than a specialist precision manufacturer. Its current ammunition business emphasizes renewed investment in manufacturing, quality and the Remington name while retaining its historical sporting-market identity.
Nosler is much younger than Remington but has an especially influential history in premium hunting bullets. John A. Nosler founded the company in Oregon in 1948 after a 1946 moose hunt convinced him that existing hunting bullets did not provide the combination of expansion and penetration he wanted.
His solution became the famous Nosler Partition bullet. That origin story still reflects the company's positioning today.
Nosler focuses heavily on premium hunting, long-range and precision-oriented products, including bullets, loaded ammunition and component brass. Important Nosler designs introduced over the years include the Partition, Ballistic Tip, AccuBond, AccuBond Long Range, E-Tip and RDF families.
Founded by Joyce Hornady in 1949, Hornady is headquartered in Grand Island, Nebraska and has developed into one of the most prominent American manufacturers of bullets, ammunition and reloading equipment.
Hornady's reputation is particularly tied to product and projectile innovation. Its ammunition portfolio covers hunting, precision/target shooting and personal-defense applications, while the company's reloading business includes presses, dies, measuring equipment and other tools for handloaders.
Federal Ammunition traces its modern history to 1922, when investors led by Charles L. Horn acquired the ammunition operation in Anoka, Minnesota and established Federal Cartridge Corporation. Federal remains based around its historic Anoka manufacturing operation.
Federal started primarily with shotshell and rimfire products but developed into an unusually comprehensive ammunition manufacturer.
The company says it now produces thousands of specialized shotshell, centerfire and rimfire loads for hunters and shooters. Its "Premium" concept dates to 1976, when Federal began combining high-end components from specialist manufacturers into premium factory-loaded ammunition.
Grain Weights and Bullet Types
Popular .338 RUM Grain Weights
- 200 Grain: A lighter .338-caliber option. This weight is typically associated with expanding soft-point and other hunting-oriented projectile designs. Published loading references include 200-grain bullets for the .338 RUM.
- 210 Grain: Another relatively light option for the cartridge, including premium controlled-expansion designs such as the Nosler Partition.
- 225 Grain: One of the cartridge's versatile mid-weight choices. Available projectile designs include traditional soft points as well as premium copper and controlled-expansion bullets. Barnes, for example, documents 225-grain TSX and TTSX projectiles for the .338 RUM.
- 250 Grain: A signature heavy-bullet weight for 338 Rem Ultra Mag ammunition. Remington catalogs a 250-grain Core-Lokt PSP load, while Barnes lists 250-grain TSX and LRX projectiles for the cartridge.
- 300 Grain: At the heavy end of the spectrum, 300-grain bullets are primarily associated with specialized high-BC and match-style projectiles. Alliant publishes .338 RUM data featuring a 300-grain Sierra MatchKing.
Common .338 Rem Ultra Mag Bullet Types
- Soft Point (SP/PSP): Traditional soft-point and pointed-soft-point bullets feature an exposed lead tip designed for expansion. Remington's Core-Lokt PSP is a prominent example of this traditional .338 RUM hunting-bullet configuration.
- Controlled-Expansion Bullets: Premium hunting bullets such as the Nosler Partition use specialized construction intended to balance expansion with penetration and weight retention. Published .338 RUM data include both 210- and 250-grain Partition projectiles.
- Monolithic Copper Bullets: Lead-free designs such as the Barnes TSX, TTSX, and LRX use copper construction and are offered in several weights suitable for the .338 RUM, including 225- and 250-grain options.
- Boat-Tail Bullets: Boat-tail designs taper toward the bullet's base to improve aerodynamic characteristics. They appear in both hunting and precision-oriented .338-caliber projectiles, including Barnes TTSX/LRX and Speer BTSP designs documented for the cartridge.
- Match / High-BC Bullets: Heavy match bullets emphasize aerodynamic efficiency and precision. The Sierra MatchKing is one example, with published .338 RUM data covering both 250- and 300-grain versions.
338 Rem Ultra Mag Ammo FAQs
QUESTION: What is .338 Remington Ultra Magnum ammo?
ANSWER: .338 Remington Ultra Magnum ammo, commonly called .338 RUM ammo or 338 Rem Ultra Mag ammunition, is a centerfire rifle cartridge developed by Remington. It uses a beltless, rebated-rim, bottleneck case and a .338-inch-diameter projectile. SAAMI lists the cartridge under the official designation 338 Remington Ultra Magnum
QUESTION: Is .338 RUM the same as .338 Remington Ultra Magnum?
ANSWER: Yes. .338 RUM, 338 Rem Ultra Mag, and .338 Remington Ultra Magnum are common shortened names for the same cartridge. When shopping for ammunition, however, always verify the exact cartridge designation stamped on the firearm and ammunition because other .338-caliber cartridges are not interchangeable.
QUESTION: What is .338 Remington Ultra Magnum ammo commonly used for?
ANSWER: The 338 Remington Ultra Magnum is primarily associated with long-range shooting and hunting applications where shooters select a powerful .338-caliber magnum cartridge. Bullet construction and grain weight vary considerably, so ammunition should be selected for its manufacturer's stated application.
QUESTION: What are common .338 RUM ammo grain weights?
ANSWER: A variety of bullet weights have been produced or documented for 338 RUM ammunition. Examples include lighter 180-grain projectiles as well as heavier 225-grain and 250-grain bullets. Nosler publishes data for a 180-grain AccuBond, while Barnes documents 225-grain TSX/TTSX and 250-grain TSX/LRX projectiles.
QUESTION: What bullet types are available for .338 Rem Ultra Mag ammunition?
ANSWER: Depending on the manufacturer and current availability, 338 Rem Ultra Mag ammo may use expanding hunting bullets, bonded bullets, polymer-tipped projectiles, monolithic copper bullets, boat-tail bullets, and other specialized designs. Barnes, for example, documents TSX, TTSX, and LRX .338-caliber projectiles for the cartridge.
QUESTION: What is the bullet diameter of .338 RUM ammunition?
ANSWER: The .338 Remington Ultra Magnum uses .338-caliber projectiles. Current SAAMI specifications list a nominal barrel groove diameter of .338 inch (8.59 mm) for the cartridge.
QUESTION: Is .338 RUM ammo the same as .338 Lapua Magnum ammo?
ANSWER: No. .338 RUM ammo and .338 Lapua Magnum ammo are different cartridges with different case specifications. They should not be treated as interchangeable simply because both use .338-caliber projectiles. Always use the exact ammunition specified by the firearm manufacturer.
QUESTION: Is .338 Remington Ultra Magnum the same as .338 Winchester Magnum?
ANSWER: No. 338 Remington Ultra Magnum ammunition and 338 Winchester Magnum ammunition are separate cartridges. SAAMI maintains distinct cartridge and chamber specifications for the .338 Remington Ultra Magnum and .338 Winchester Magnum.
QUESTION: What is the maximum overall length of a .338 Rem Ultra Mag cartridge?
ANSWER: SAAMI's current specification shows a maximum cartridge overall length of 3.600 inches (91.44 mm) for the .338 Remington Ultra Magnum. Published Nosler data likewise identifies 3.600 inches as the maximum SAAMI overall cartridge length.
QUESTION: Is .338 Remington Ultra Magnum a belted magnum cartridge?
ANSWER: No. One characteristic distinguishing the 338 Rem Ultra Mag cartridge from traditional belted magnums is its beltless, rebated-rim case design.
QUESTION: What is the difference between 225 grain and 250 grain .338 RUM ammo?
ANSWER: The primary difference is projectile weight: a 250-grain .338 RUM bullet is heavier than a 225-grain bullet. Projectile construction, ballistic coefficient, velocity, and intended application can also differ significantly. For example, Barnes publishes .338 RUM data for both 225- and 250-grain projectiles with different ballistic characteristics.
QUESTION: What should I look for when comparing .338 RUM ammunition?
ANSWER: When comparing 338 Remington Ultra Magnum ammo, useful factors include bullet weight, projectile construction, manufacturer, intended application, and published ballistic characteristics. Buyers should also confirm that the ammunition's exact cartridge designation matches the firearm manufacturer's specifications.
QUESTION: Why is .338 Remington Ultra Magnum ammo sometimes called 338 Ultra Mag ammo?
ANSWER: 338 Ultra Mag ammo is an informal shortened search term frequently used for .338 Remington Ultra Magnum ammunition.