| .257 Weatherby Magnum | ||||||||||||||||||||
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 .257 Weatherby Magnum (center) with .308 Winchester (left) and .375 H&H Magnum (right). | ||||||||||||||||||||
| Type | Rifle | |||||||||||||||||||
| Place of origin | United States | |||||||||||||||||||
| Production history | ||||||||||||||||||||
| Designer | Roy Weatherby | |||||||||||||||||||
| Designed | 1944 | |||||||||||||||||||
| Manufacturer | Weatherby | |||||||||||||||||||
| Produced | 1948–present | |||||||||||||||||||
| Specifications | ||||||||||||||||||||
| Parent case | .375 H&H Magnum | |||||||||||||||||||
| Case type | Belted Magnum | |||||||||||||||||||
| Bullet diameter | .257 in (6.5 mm) | |||||||||||||||||||
| Neck diameter | .283 in (7.2 mm) | |||||||||||||||||||
| Shoulder diameter | .492 in (12.5 mm) | |||||||||||||||||||
| Base diameter | .512 in (13.0 mm) | |||||||||||||||||||
| Rim diameter | .5315 in (13.50 mm) | |||||||||||||||||||
| Rim thickness | .051 in (1.3 mm) | |||||||||||||||||||
| Case length | 2.545 in (64.6 mm) | |||||||||||||||||||
| Overall length | 3.209 in (81.5 mm) | |||||||||||||||||||
| Case capacity | 84 gr H2O (5.4 cm3) | |||||||||||||||||||
| Rifling twist | 1 in 10 in (250 mm) | |||||||||||||||||||
| Primer type | Large Rifle (magnum) | |||||||||||||||||||
| Maximum pressure | 65,000 psi (450 MPa) | |||||||||||||||||||
| Ballistic performance | ||||||||||||||||||||
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| Test barrel length: 26 in (660 mm) Source(s): Weatherby[1] | ||||||||||||||||||||
The .257 Weatherby Magnum is a .257 caliber (6.53 mm) belted bottlenecked cartridge. It is one of the original standard length magnums developed by shortening the .375 H&H Magnum case to approx. 2.5 in (64 mm). Of the cartridges developed by Roy Weatherby, the .257 Weatherby Magnum was known to have been his favorite, and the cartridge currently ranks third in Weatherby cartridge sales, after the .30-378 Weatherby Magnum and the .300 Weatherby Magnum.[2]
The .257 Weatherby Magnum is capable of firing a 115 gr (7.5 g) Nosler Ballistic Tip bullet at 3,400 ft/s (1,036 m/s) generating 2,952 ft⋅lbf (4,002 J) of energy[3] which is comparable to factory loadings of the .30-06 Springfield and the .35 Whelen in terms of energy.
Discrepancies between the metric and U.S. diameters of the bullet may cause some confusion. A .257 bullet has a metric bullet diameter of 6.53 mm. However, in Europe cartridge designation nomenclature for a large part relies on the bore diameter. As the bore diameter of the .257 Weatherby Magnum is .250 inches this would make it a 6.35 mm caliber cartridge which uses 6.5 mm bullets (not to be confused with 6.5 mm caliber cartridges which use 6.7 mm/.264" bullets).
- ^ "Weatherby Inc". Archived from the original on 16 February 2005. Retrieved 31 July 2007.
- ^ Layne Simpson. "In Praise of The .257 Weatherby Magnum". Shooting Times Magazine. Intermedia Outdoors Inc. Archived from the original on 5 April 2009. Retrieved 19 December 2010.
- ^ ".257 Wby. Mag". Weatherby Inc. Archived from the original on 30 November 2010. Retrieved 19 December 2010.