Lindcott Armory Rifle · SAAMI
.338-378 Weatherby Magnum
A .338 built on the .378 Weatherby Magnum parent case — the largest commercially produced .338-caliber cartridge.
- Caliber
- 0.338″ · 8.585 mm
- Introduced
- 1998
- Case
- Belted
- Parent
- .378 Weatherby Magnum
- Primary use
- hunting_large_game, hunting_dangerous_game, long_range_hunting
- Status
- Active
- Introduced
- 1998
- Type
- Rifle
- Origin
- United States
- Inventor
- Roy Weatherby
- Manufacturer
- Weatherby
- Standard
- SAAMI
- Status
- Active
- Availability
- Specialty
- Case capacity
- 131 gr H₂O
- Twist (typical)
- 1:10
- Primer
- Large Rifle Magnum
- Case type
- Belted
- Max pressure
- 63,817 psi
- Eff. range
- 600 yd
- Recoil
- 40–55 ft·lb
Ballistics
Real trajectory computed from a representative load — Weatherby Select Plus 250 gr, 2,960 fps, BC 0.318 G7 · 100 yd zero.
| Range | Velocity | Energy | Drop (in) | Drop (MOA) |
|---|---|---|---|---|
| 0 yd | 2959 | 4860 | -1.5″ | — |
| 100 yd | 2813 | 4392 | 0.0″ | 0.0 |
| 200 yd | 2670 | 3957 | -2.9″ | -1.4 |
| 300 yd | 2530 | 3554 | -10.7″ | -3.4 |
| 400 yd | 2395 | 3182 | -23.9″ | -5.7 |
| 500 yd | 2263 | 2842 | -43.2″ | -8.3 |
| 600 yd | 2135 | 2531 | -69.3″ | -11.0 |
| 700 yd | 2012 | 2246 | -103.0″ | -14.0 |
| 800 yd | 1891 | 1985 | -145.4″ | -17.4 |
Point-mass G7/G1 drag model, standard atmosphere — within ~2% of reference solvers to 1000 yd; real barrels and conditions vary. Open in Ballistic Compare →
Performance
Buy links open .338-378 Weatherby Magnum ammunition at Rivertown Munitions.
Dimensionscase measurements · scale drawing · size vs familiar rounds
Case dimensions — the scale drawing at the top of the page is built from these.
Wikipedia · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 8.59 | 0.338 | · |
| Neck ⌀ | 9.40 | 0.370 | ~ |
| Shoulder ⌀ | 14.25 | 0.561 | · |
| Shoulder angle | — | — | |
| Base ⌀ | 14.78 | 0.582 | · |
| Rim ⌀ | 14.71 | 0.579 | · |
| Belt ⌀ | 15.34 | 0.604 | ~ |
| Rim thickness | 1.60 | 0.063 | ~ |
| Neck length | 9.04 | 0.356 | ≈ |
| Case length | 73.86 | 2.908 | · |
| Overall length | 92.71 | 3.650 | ~ |
Size vs familiar rounds
Drawn at true 1:1 — every case is accurate relative to the others. Absolute size depends on your screen's pixel density, so measuring one against a real ruler may be off. .338-378 Weatherby Magnum is highlighted below.
Missing a dimension for .338-378 Weatherby Magnum? Some case measurements aren't in a published SAAMI/CIP drawing yet. Have a factory or reamer print? Send it → — verified hard-to-find data earns a free Lindcott sticker.
Factory loads
In production — 21 active loads across 14 brands. Top 15 shown · see all 21 →.
| Brand | Load | Grain | Bullet | FPS | ft·lb | BC |
|---|---|---|---|---|---|---|
| Weatherby | Select Plus Nosler Partition | 225 | Nosler Partition | 3,150 | 4,956 | 0.550 G1 |
| Nosler | Trophy Grade AccuBond | 225 | AccuBond | 3,150 | 4,956 | 0.278 G7 |
| Barnes | VOR-TX TTSX BT | 225 | TTSX BT | 3,100 | 4,800 | 0.215 G7 |
| Weatherby | Select Plus | 250 | Nosler AccuBond | 2,960 | 4,863 | 0.318 G7 |
| Weatherby | Select Plus SP | 200 | SP | 3,350 | 4,983 | — |
| Norma | Oryx | 225 | Oryx | 3,180 | 5,051 | — |
| Remington | Premier | 225 | Swift A-Frame | 3,180 | 5,051 | — |
| Federal | Trophy Bonded | 225 | Trophy Bonded | 3,180 | 5,051 | — |
| Hornady | Superformance Interlock SP | 225 | Interlock SP | 3,150 | 4,956 | — |
| Norma | Vulkan | 250 | Vulkan | 3,050 | 5,163 | — |
| Remington | Core-Lokt | 250 | Core-Lokt | 3,050 | 5,163 | — |
| Federal | Trophy Bonded | 250 | Trophy Bonded | 3,050 | 5,163 | — |
| Weatherby | Select | 250 | Hornady SP | 2,960 | 4,863 | — |
| Norma | Classic | 250 | Soft Point | 2,900 | 4,668 | — |
| Kynoch | Classic | 250 | Soft Point | 2,900 | 4,668 | — |
Velocities are manufacturer-stated (test-barrel). Discontinued loads dimmed.
Suitable powders
2 reloading powders listed for .338-378 Weatherby Magnum, fastest to slowest. Cross-reference in the finder →
Reloading costestimate cost per round vs factory
Estimate your cost per round and how it compares to factory. Inputs are yours — nothing is stored.
Cost estimate only — not load data. Charge weight is your input; follow published manuals for safe charges.
Firearms chambered in .338-378 Weatherby Magnum
1 model in the database chamber .338-378 Weatherby Magnum. Browse all →
Lineage
Connected reference
History
Developed by Weatherby as part of their tradition of extreme high-velocity cartridges. The .338-378 was initially a wildcat embraced by hunters seeking maximum .338-caliber performance before Weatherby standardized it in 1998. It targets dangerous game hunters who want the penetration and sectional density of .338-caliber bullets with velocity approaching .378 Weatherby levels. Recoil is extreme — typically exceeding 80 ft-lbs in a standard rifle — requiring either a very heavy rifle or a muzzle brake.
FAQs
- What twist rate does .338-378 Weatherby Magnum use?
- .338-378 Weatherby Magnum typically uses a 1:10 twist rate.
- What bullet diameter is .338-378 Weatherby Magnum?
- .338-378 Weatherby Magnum uses a 0.338″ (8.585 mm) diameter bullet.
- Is .338-378 Weatherby Magnum still in production?
- .338-378 Weatherby Magnum is active; typical availability is specialty.
- What is .338-378 Weatherby Magnum used for?
- .338-378 Weatherby Magnum is primarily used for hunting_large_game, hunting_dangerous_game, long_range_hunting.
- What is .338-378 Weatherby Magnum based on?
- .338-378 Weatherby Magnum is derived from the .378 Weatherby Magnum case.
- What are the best powders for .338-378 Weatherby Magnum?
- Reloading powders commonly listed for .338-378 Weatherby Magnum include Reloader 25, Reloader 33.
Sources & provenance
Data & sources. Specs compiled from the Lindcott Armory reference; availability counted from 21 live factory loads; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →