.257 Weatherby Magnum

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.257 Weatherby Magnum

Type	Rifle
Place of origin	USA
Production history
Designer	Roy Weatherby
Designed	1944
Manufacturer	Weatherby
Produced	1944-Present
Specifications
Parent case	.300 H&H Magnum
Bullet diameter	.257 in (6.5 mm)
Neck diameter	.288 in (7.3 mm)
Shoulder diameter	.496 in (12.6 mm)
Base diameter	.514 in (13.1 mm)
Rim diameter	.534 in (13.6 mm)
Case length	2.560 in (65.0 mm)
Primer type	large rifle magnum
Ballistic performance
Bullet weight/type	Velocity	Energy
87 gr (5.6 g) SP	3,825 ft/s (1,166 m/s)	2,826 ft·lbf (3,832 J)
100 gr (6.5 g) SP	3,602 ft/s (1,098 m/s)	2,881 ft·lbf (3,906 J)
117 gr (7.6 g) BST	3,400 ft/s (1,000 m/s)	2,952 ft·lbf (4,002 J)
120 gr (7.8 g) Partition	3,305 ft/s (1,007 m/s)	2,910 ft·lbf (3,950 J)
Source: Weatherby ^[1]

The .257 Weatherby Magnum was introduced as a wildcat during the mid 1940s when Roy Weatherby was building custom rifles around war surplus '03 Springfield and the '98 Mauser actions. It was always his favorite cartridge.

The .257 Weatherby Magnum cartridge case itself a shortened version of the .300 H&H Magnum case necked down to .257 caliber and blown out the full length of the case which then sports a double radius shoulder and shortened to 2.545" with a long neck.

The 257 Weatherby Magnum is an extremely flat-shooting dual-purpose cartridge and is the fastest of all commercially available 25 caliber cartridges, sending a 75-grain (4.9 g) bullet out the muzzle at 3,900 feet per second (1,190 m/s) for varmints and able to send a 115-grain (7.5 g) bullet out the muzzle at 3,400 feet per second (1,040 m/s) for deer sized game. It is well suited for plains hunting and other areas where very long range shooting is expected.