Rifle · SAAMI
.257 Weatherby Magnum
Extremely fast and flat-shooting magnum.
- Caliber
- 0.257″ · 6.528 mm
- Introduced
- 1944
- Case
- Belted
- Parent
- .375 H&H Magnum
- Primary use
- Hunting, Varmint
- Status
- Active
- Introduced
- 1944
- Type
- Rifle
- Origin
- United States
- Inventor
- Roy Weatherby
- Manufacturer
- Weatherby
- Standard
- SAAMI
- Status
- Active
- Availability
- Moderate
- Case capacity
- 82 gr H₂O
- Twist (typical)
- 1:10
- Primer
- Large Rifle Magnum
- Case type
- Belted
- Max pressure
- 62,500 psi, SAAMI transducer
- Eff. range
- 500 yd
- Max range
- 4500 yd
- Recoil
- 16–22 ft·lb
Introduced by Weatherby
Ballistics
Published velocity/energy data isn't available for .257 Weatherby Magnum. Parent case: .375 H&H Magnum.
Performance
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 ⌀ | 6.53 | 0.257 | ✓ |
| Neck ⌀ | 7.24 | 0.285 | ✓ |
| Shoulder ⌀ | 12.50 | 0.492 | ✓ |
| Shoulder angle | 25.5° | — | ~ |
| Base ⌀ | 13.01 | 0.512 | ✓ |
| Rim ⌀ | 13.50 | 0.531 | ✓ |
| Belt ⌀ | 13.49 | 0.531 | ✓ |
| Rim thickness | 1.30 | 0.051 | ✓ |
| Neck length | 8.13 | 0.320 | ≈ |
| Case length | 64.74 | 2.549 | ✓ |
| Overall length | 81.51 | 3.209 | ✓ |
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. .257 Weatherby Magnum is highlighted below.
Factory loads
Being verified
Advertised FPS, energy, and BC are withheld until loads clear verification.
Suitable powders
3 reloading powders listed for .257 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 .257 Weatherby Magnum
Lineage
Connected reference
History
Developed by Roy Weatherby in 1944 as his first commercial magnum cartridge. Based on blown-out .375 H&H case necked to .257. Weatherby's personal favorite cartridge. Delivers high muzzle velocity and a flat trajectory. Popular with western hunters and long-range shooters. Heavy recoil for a .25 caliber and significant barrel wear, but dramatic performance.
FAQs
- What twist rate does .257 Weatherby Magnum use?
- .257 Weatherby Magnum typically uses a 1:10 twist rate.
- What bullet diameter is .257 Weatherby Magnum?
- .257 Weatherby Magnum uses a 0.257″ (6.528 mm) diameter bullet.
- Is .257 Weatherby Magnum still in production?
- .257 Weatherby Magnum is active; typical availability is moderate.
- What is .257 Weatherby Magnum used for?
- .257 Weatherby Magnum is primarily used for hunting, varmint.
- What is .257 Weatherby Magnum based on?
- .257 Weatherby Magnum is derived from the .375 H&H Magnum case.
- What are the best powders for .257 Weatherby Magnum?
- Reloading powders commonly listed for .257 Weatherby Magnum include Norma MRP, N170, Reloader 25.
Sources & provenance
- Standard SAAMI — ANSI/SAAMI Z299 — Cartridge & Chamber Drawings archived
- Standard SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) — ANSI/SAAMI Z299.4 – 2015 (Centerfire Rifle) — Velocity & Pressure / Cartridge & Chamber Drawings · grain_ballistics, representative_gun archived
- Standard SAAMI — SAAMI cartridge & chamber drawing — .257 Weatherby Magnum
- Manufacturer Nosler — 257 Wby Mag 110gr AccuBond Trophy Grade Ammunition · representative_gun, grain_ballistics archived
- Manufacturer Weatherby — Weatherby Ballistics Charts — 257 WBY MAG · grain_ballistics, representative_gun
Data & sources. Specs compiled from the Lindcott Armory reference; availability counted from 43 live factory loads; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →
