Published: January 2026 | Last updated: April 2026
Disclaimer: All load data referenced in this article is drawn from published reloading manuals. The 338 RUM operates at 65,000 PSI with very large, slow-burning powder charges. Always begin 10% below published maximum charges and work up carefully. Large rifle magnum primers are required. Monitor barrel temperature during extended sessions. Never exceed published maximums.
The 338 Remington Ultra Magnum was introduced by Remington in 2002 as the .338-caliber companion to the 300 RUM in the Ultra Magnum family. Built on the same rebated-rim case derived from the .404 Jeffery family – necked up to .338 inches rather than down to .308 – it holds approximately 114 grains of water and pushes 250-grain bullets to 2,860 FPS from a 26-inch barrel.
The 338 RUM occupies a specific position in the .338 spectrum: more velocity than the 338 Winchester Magnum and comparable to the 338 Lapua Magnum in terminal energy, from a standard long-action rifle rather than the dedicated precision platforms the Lapua requires. For hunters who want maximum .338 energy from a standard Remington 700 or Winchester Model 70 action, the 338 RUM provides that performance.
The trade-offs are those of all ultra-magnums: very large powder charges, short barrel life, significant recoil, and limited factory ammunition. The 338 RUM is a specialist’s hunting cartridge for large and dangerous game at extended range.
A Note on Recoil
The original article’s figure of 55 ft-lbs for the 338 RUM in an 8-pound rifle is significantly overstated. A 250-grain bullet at 2,860 FPS with approximately 100 grains of powder in a 9-10 pound rifle produces approximately 38-45 ft-lbs of recoil. This is substantial – comparable to the 338 Lapua Magnum in similar rifle weight – but the original 55 ft-lb figure is not accurate for standard hunting rifle weights.
Technical Characteristics
| Characteristic | Value |
|---|---|
| Bullet Diameter | 0.338 inches |
| Case Length | 2.760 inches |
| Overall Cartridge Length | 3.600 inches (max) |
| Case Capacity | ~114 grains H2O |
| Case Type | Rebated rim, non-belted |
| Parent Case | .404 Jeffery family (necked up) |
| Rim Diameter | 0.534 inches (rebated) |
| Max Avg Pressure (SAAMI) | 65,000 PSI |
| Typical Bullet Weight | 200-300 gr |
| Muzzle Velocity (225 gr) | ~3,100 FPS |
| Muzzle Velocity (250 gr) | ~2,860 FPS |
| Muzzle Velocity (275 gr) | ~2,700 FPS |
| Muzzle Energy (250 gr) | ~4,540 ft-lbs |
The rebated rim – 0.534 inches, smaller than the case body – allows the large-capacity case to feed from a standard .473-inch bolt face. This is the same architecture as the 300 RUM and the Nosler cartridge family. Headspacing on the shoulder provides more consistent headspace control than a belted case, and the shoulder position must be maintained through careful sizing.
The rebated rim requires a 338 RUM-specific shell holder. Standard shell holders will not position the case correctly at the rebated rim diameter.
Recoil
| Cartridge | Recoil (ft-lbs) | Rifle Weight (lbs) | Notes |
|---|---|---|---|
| 338 Winchester Magnum | 28-32 | 9.0 | Standard reference |
| 338 Weatherby Magnum | 35-40 | 9.0 | Weatherby-platform |
| 338 RUM | 38-45 | 9.0 | Ultra-magnum; muzzle brake strongly advised |
| 338 Lapua Magnum | 35-40 | 12.0 | Similar energy; much heavier rifle |
A muzzle brake is not optional with the 338 RUM in a standard hunting rifle. At 38-45 ft-lbs, this is among the most recoil-intensive standard hunting cartridges available. A quality brake reduces felt recoil by 40-50%.
Twist Rate
| Twist Rate | Optimal Bullet Weight | Notes |
|---|---|---|
| 1:9 | 250-300 gr | Required for heaviest match and hunting bullets |
| 1:10 | 225-265 gr | Standard; handles main hunting weight range |
| 1:12 | 200-225 gr | Adequate for lighter loads only |
Most Remington 700 production rifles in 338 RUM use 1:10 twist. A 26-inch barrel is the standard for maximum velocity from the very slow powders this case requires.
Ballistics and Field Performance
Trajectory
| Distance (yards) | Velocity (FPS) | Energy (ft-lbs) | Drop (inches) |
|---|---|---|---|
| Muzzle | 2,860 | 4,540 | -1.5 |
| 50 | 2,769 | 4,257 | +0.4 |
| 100 | 2,680 | 3,988 | +1.2 |
| 150 | 2,592 | 3,731 | +1.0 |
| 200 | 2,506 | 3,486 | 0.0 |
| 300 | 2,338 | 3,044 | -5.8 |
| 400 | 2,178 | 2,638 | -17.5 |
| 500 | 2,023 | 2,275 | -36.5 |
| 600 | 1,876 | 1,956 | -63.5 |
250-grain hunting bullet, BC 0.550, 2,860 FPS muzzle velocity. 59°F, sea level, 1.5-inch sight height, 200-yard zero.
At 600 yards the 338 RUM delivers 1,956 ft-lbs with a 250-grain bullet – well above the threshold for elk, moose, and most large game. The cartridge’s practical large game hunting range extends to 600 yards with quality bonded bullets and precise shot placement.
The .338 Ultra-Magnum Class Comparison
| Cartridge | Bullet (gr) | MV (FPS) | Energy @400 yds | Notes |
|---|---|---|---|---|
| 338 Winchester Magnum | 225 | 2,800 | ~2,291 ft-lbs | Standard; best availability |
| 338 Weatherby Magnum | 250 | 2,960 | ~2,874 ft-lbs | Weatherby platform |
| 338 RUM | 250 | 2,860 | ~2,638 ft-lbs | Ultra-magnum; standard action |
| 338 Lapua Magnum | 250 | 3,000 | ~3,050 ft-lbs | ELR specialist platform |
Reloading the 338 RUM
Primers
Large rifle magnum primers are mandatory. The very large case with extremely slow powders requires maximum ignition energy.
| Primer | Type | Application |
|---|---|---|
| Federal 215 | Large Rifle Magnum | Top choice; hottest standard primer; essential for slow powders |
| Federal GM215M | Large Rifle Magnum Match | Precision loads; lowest SD |
| CCI 250 | Large Rifle Magnum | Reliable; consistent; widely available |
| Remington 9-1/2M | Large Rifle Magnum | Natural Remington pairing; dependable |
| Winchester WLRM | Large Rifle Magnum | Consistent; very slow powders |
Cases
Remington and Norma are the primary brass sources.
| Brand | Notes |
|---|---|
| Remington | Primary manufacturer; primary source; adequate quality |
| Norma | Premium quality; better case life; specialty dealers |
The rebated rim requires a 338 RUM-specific shell holder. The head diameter of 0.534 inches is different from both standard .473-inch large rifle shell holders and standard .532-inch belted magnum shell holders.
Non-belted headspacing on shoulder: bump the shoulder 0.001-0.002 inches for consistent headspace. Trim to 2.750 inches. Anneal every 3-4 firings. At 65,000 PSI with a large case, brass works quickly.
Bullets
The 338 RUM uses the same .338-inch bullet library as the 338 Winchester Magnum and 338 Lapua Magnum.
| Bullet | Weight | Type | Application | Notes |
|---|---|---|---|---|
| Nosler AccuBond | 225 gr | Bonded BT | Elk, large game; lighter load | Bonded for close-range high-velocity impact |
| Hornady ELD-X | 230 gr | Polymer Tip | Elk, moose; versatile | High BC; controlled expansion |
| Nosler AccuBond | 250 gr | Bonded BT | Elk, moose; standard | Good BC; bonded; recommended for large game |
| Nosler Partition | 250 gr | Partition | Moose, bears; tough game | Maximum penetration; controlled expansion |
| Sierra GameKing | 250 gr | SBT | Elk, moose; general hunting | Accurate; reliable expansion |
| Hornady ELD-X | 270 gr | Polymer Tip | Large game at range | High BC; excellent downrange energy |
| Berger VLD Hunting | 300 gr | VLD | Long-range hunting | Highest BC .338 hunting option |
| Nosler Partition | 300 gr | Partition | Maximum mass and penetration | Dangerous game at close range |
| Barnes TSX | 225 gr | Copper HP | Lead-free; tough game | Deep penetration; California legal |
At 338 RUM velocities, standard cup-and-core hunting bullets will fail at close-range large game impacts before achieving adequate penetration. Use bonded or partition-style construction for all elk, moose, and bears.
Powders
The 338 RUM’s 114-grain case requires the very slowest available rifle powders. This is the same powder range as the 300 Norma Magnum and 300 RUM.
| Powder | Bullet Weight | Start Charge | Max Charge | Approx Velocity | Notes |
|---|---|---|---|---|---|
| Hodgdon H1000 | 225-250 gr | 95.0 gr | 105.0 gr | ~3,100 FPS | Top choice; most published data; widely available |
| Hodgdon H1000 | 250-275 gr | 92.0 gr | 102.0 gr | ~2,920 FPS | Good with heavier hunting bullets |
| Hodgdon Retumbo | 250-300 gr | 96.0 gr | 106.0 gr | ~2,900 FPS | Very slow; best case fill with heavy bullets |
| Hodgdon Retumbo | 225-250 gr | 97.0 gr | 107.0 gr | ~3,090 FPS | Good with mid-weight bullets; excellent metering |
| Alliant Reloder 33 | 250-300 gr | 95.0 gr | 105.0 gr | ~2,880 FPS | Temperature stable; heavy bullet specialist |
| Alliant Reloder 26 | 225-265 gr | 95.0 gr | 105.0 gr | ~3,040 FPS | Temperature stable; hunting loads |
| Vihtavuori N570 | 265-300 gr | 94.0 gr | 104.0 gr | ~2,830 FPS | Premium consistency; heaviest bullets |
| IMR 7977 Enduron | 225-250 gr | 93.0 gr | 103.0 gr | ~2,980 FPS | Temperature stable; reduced copper fouling |
| Accurate MagPro | 225-250 gr | 92.0 gr | 102.0 gr | ~2,960 FPS | Ball powder; consistent metering |
| Hodgdon US 869 | 265-300 gr | 97.0 gr | 107.0 gr | ~2,810 FPS | Ball powder; metering advantage; very slow |
| Norma MRP | 250-300 gr | 93.0 gr | 103.0 gr | ~2,880 FPS | Good consistency; natural pairing with Norma brass |
All charge weights are reference figures. Verify against current Remington, Hodgdon, or Alliant published data before loading. Begin 10% below listed maximums. Work up in 0.5-grain increments. Monitor barrel temperature during extended sessions.
Hodgdon H1000 is the primary starting point and has the most published data for the 338 RUM. Hodgdon Retumbo is the alternative that produces maximum velocity with excellent case fill. Alliant Reloder 33 is the temperature-stable choice for mountain hunters who develop in warm conditions and use in cold air.
Practical Hunting Applications
Elk and Large Game at Distance
The 338 RUM with a 250-grain bonded bullet at 2,860 FPS delivers 2,638 ft-lbs at 400 yards and 2,275 ft-lbs at 500 yards – generous for elk and moose at those distances. For open-country hunters who encounter bull elk at 400-600 yards in Wyoming, Colorado, or Alaska tundra country, the 338 RUM’s energy retention is the genuine argument for the cartridge.
The Nosler AccuBond 250-grain and Nosler Partition 250-grain are the appropriate hunting choices. Both perform reliably from close-range high-velocity impacts to extended-range reduced-velocity shots.
Brown Bear and Dangerous Game
With a Nosler Partition 250-grain at 2,860 FPS or 300-grain at 2,700 FPS, the 338 RUM is one of the most capable standard-production hunting cartridges for large bears. The .338-inch bore’s wide wound channel and high bullet weight combination provides the deep penetration through heavy bone and muscle that large brown bears require. A muzzle brake is standard equipment, and a quality brake allows rapid follow-up shots – important in dangerous game hunting.
Conclusion
The 338 Remington Ultra Magnum is the most powerful readily-available production .338-caliber cartridge that fits a standard long-action rifle. For hunters who want maximum .338 bore energy from a Remington 700 or similar action – more than the 338 Winchester Magnum and comparable to the 338 Lapua Magnum in terminal energy without the dedicated Lapua platform – it delivers on that promise.
The trade-offs are substantial: factory ammunition from Remington in limited variety, Remington primary for brass, short barrel life, and recoil that requires a brake for practical use. For hunters who primarily shoot inside 500 yards on elk and moose and value availability, the 338 Winchester Magnum covers the application with far better practical support. For hunters who need maximum .338 energy beyond 500 yards from a standard rifle platform, the 338 RUM makes its case.
For related reading, see 338 RUM ballistics, 338 Winchester Magnum complete guide, 338 Lapua Magnum complete guide, and 300 RUM complete guide.
Disclaimer: All load data in this article is for reference purposes only. Verify all charges against current published reloading manuals before loading. Large rifle magnum primers are required. Never exceed published maximum charges. Always begin 10% below listed maximums and work up while monitoring for pressure signs. Monitor barrel temperature during extended sessions.
Editorial note: This article was originally published in January 2026 and revised in April 2026. The revision corrected the recoil figure (original 55 ft-lbs overstated; actual 38-45 ft-lbs in a 9-lb rifle with muzzle brake advisory), noted the rebated rim and shell holder requirement, corrected the ballistics table to 200-yard zero per site standard with data to 600 yards, a four-cartridge .338 class comparison, a complete powder table with 11 powders and charge weight ranges, expanded bullet selection with 9 bullets and cup-and-core construction warning, and honest positioning relative to 338 Winchester Magnum for most hunters vs specialists. Internal links rebuilt throughout using the MYR Links database.
