Lindcott Armory Rifle · SAAMI
.378 Weatherby Magnum
Roy Weatherby's .375-caliber belted magnum and the parent case for the .460 Weatherby.
- Caliber
- 0.375″ · 9.525 mm
- Introduced
- 1953
- Case
- Belted
- Parent
- .416 Rigby
- Primary use
- Hunting
- Status
- Active
- Introduced
- 1953
- Type
- Rifle
- Origin
- United States
- Inventor
- Roy Weatherby
- Manufacturer
- Weatherby
- Standard
- SAAMI
- Status
- Active
- Availability
- Specialty
- Case capacity
- 131 gr H₂O
- Twist (typical)
- 1:12
- Primer
- Large Rifle Magnum
- Case type
- Belted
- Max pressure
- 62,000 psi
- Eff. range
- 400 yd
- Max range
- 1000 yd
- Recoil
- 50–70 ft·lb
Ballistics
Real trajectory computed from a representative load — Hornady Precision Hunter ELD-X 270 gr, 3,180 fps, BC 0.320 G7 · 100 yd zero.
| Range | Velocity | Energy | Drop (in) | Drop (MOA) |
|---|---|---|---|---|
| 0 yd | 3179 | 6058 | -1.5″ | — |
| 100 yd | 3028 | 5496 | 0.0″ | 0.0 |
| 200 yd | 2880 | 4973 | -2.3″ | -1.1 |
| 300 yd | 2736 | 4488 | -8.8″ | -2.8 |
| 400 yd | 2596 | 4040 | -19.9″ | -4.8 |
| 500 yd | 2460 | 3626 | -36.2″ | -6.9 |
| 600 yd | 2327 | 3245 | -58.3″ | -9.3 |
| 700 yd | 2198 | 2897 | -86.7″ | -11.8 |
| 800 yd | 2073 | 2576 | -122.5″ | -14.6 |
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 .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.
SAAMI · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 9.53 | 0.375 | · |
| Neck ⌀ | 10.13 | 0.399 | · |
| Shoulder ⌀ | 14.22 | 0.560 | · |
| Shoulder angle | 22.2° | — | ~ |
| Base ⌀ | 14.78 | 0.582 | · |
| Rim ⌀ | 14.71 | 0.579 | · |
| Belt ⌀ | 15.32 | 0.603 | ~ |
| Rim thickness | 1.60 | 0.063 | · |
| Neck length | 9.40 | 0.370 | ≈ |
| Case length | 73.99 | 2.913 | ~ |
| 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. .378 Weatherby Magnum is highlighted below.
Factory loads
In production — 22 active loads across 14 brands. Top 15 shown · see all 22 →.
| Brand | Load | Grain | Bullet | FPS | ft·lb | BC |
|---|---|---|---|---|---|---|
| HSM | Trophy Gold | 270 | Barnes TTSX | 3,180 | 6,062 | 0.416 G1 |
| Weatherby | Select Plus | 270 | Nosler Partition | 3,180 | 6,062 | 0.459 G1 |
| Weatherby | Select Plus Barnes TTSX BT | 270 | TTSX BT | 3,180 | 6,062 | 0.416 G1 |
| Nosler | Trophy Grade Partition | 270 | Partition | 3,180 | 6,062 | 0.459 G1 |
| Hornady | Precision Hunter ELD-X | 270 | ELD-X | 3,180 | 6,062 | 0.320 G7 |
| Barnes | VOR-TX | 270 | TTSX BT | 3,180 | 6,062 | 0.416 G1 |
| Weatherby | Select Plus Nosler AccuBond | 270 | Nosler AccuBond | 2,928 | 5,139 | 0.488 G1 |
| Weatherby | Select Plus | 270 | Nosler AccuBond | 2,925 | 5,128 | 0.488 G1 |
| Hornady | DGX Bonded | 270 | DGX Bonded | 3,180 | 6,062 | — |
| Weatherby | Select Plus Hornady SP-RP | 270 | SP-RP | 3,180 | 6,062 | — |
| Weatherby | Select | 270 | Hornady SP | 2,925 | 5,128 | — |
| Norma | Oryx | 300 | Bonded SP | 2,925 | 5,698 | — |
| Weatherby | Select Plus | 300 | SP | 2,925 | 5,698 | — |
| Weatherby | Select Plus | 300 | Hornady FMJ-RN | 2,925 | 5,698 | — |
| Winchester | Nosler AccuBond | 270 | AccuBond | 2,900 | 5,041 | — |
Velocities are manufacturer-stated (test-barrel). Discontinued loads dimmed.
Suitable powders
9 reloading powders listed for .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 .378 Weatherby Magnum
12 models in the database chamber .378 Weatherby Magnum. Browse all →
Lineage
Connected reference
History
Roy Weatherby introduced the .378 Wby Mag in 1953 on his proprietary large belted case. Weatherby's philosophy was maximum velocity at all calibers — the .378 pushes 300-grain bullets 300+ fps faster than .375 H&H, generating roughly 50% more muzzle energy. The .378 case became the parent for the .460 Weatherby Magnum, giving it outsized importance in Weatherby's cartridge lineage. Professional hunters in Africa used it for elephant and cape buffalo, though its recoil — often described as brutal even in heavy rifles — limited widespread adoption. Weatherby still manufactures ammunition and chambers the Mark V in .378.
FAQs
- What twist rate does .378 Weatherby Magnum use?
- .378 Weatherby Magnum typically uses a 1:12 twist rate.
- What bullet diameter is .378 Weatherby Magnum?
- .378 Weatherby Magnum uses a 0.375″ (9.525 mm) diameter bullet.
- Is .378 Weatherby Magnum still in production?
- .378 Weatherby Magnum is active; typical availability is specialty.
- What is .378 Weatherby Magnum used for?
- .378 Weatherby Magnum is primarily used for hunting.
- What is .378 Weatherby Magnum based on?
- .378 Weatherby Magnum is derived from the .416 Rigby case.
- What are the best powders for .378 Weatherby Magnum?
- Reloading powders commonly listed for .378 Weatherby Magnum include N170, IMR 5010, Reloader 26, LRT, among 9 suitable options.
Sources & provenance
- StandardSAAMI — SAAMI cartridge & chamber drawing — .378 Weatherby Magnumarchived
- StandardSAAMI — ANSI/SAAMI Z299 — Cartridge & Chamber Drawingsarchived
Data & sources. Specs compiled from the Lindcott Armory reference; availability counted from 22 live factory loads; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →