.240 Weatherby Magnum

The .240 Weatherby Magnum was developed in 1968 by Roy Weatherby. In the development of his own .240in/6 mm cartridge, Weatherby was significantly influenced by both the success and the limitations of the .244 H&H Magnum cartridge devised in England by his friend and colleague David Lloyd. It was the last cartridge to be designed by Roy Weatherby.[2]

.240 Weatherby Magnum
.240 Weatherby Magnum (1st from left)
TypeRifle
Place of originUSA
Production history
DesignerRoy Weatherby
Designed1968
ManufacturerWeatherby
Specifications
Bullet diameter.243 in (6.2 mm)
Neck diameter.272 in (6.9 mm)
Shoulder diameter.429 in (10.9 mm)
Base diameter.453 in (11.5 mm)
Rim diameter.472 in (12.0 mm)
Case length2.496 in (63.4 mm)
Overall length3.100 in (78.7 mm)
Case capacity64 gr H2O (4.1 cm3)
Rifling twist1 in 10 in (250 mm)
Primer typeLarge rifle
Maximum pressure65,000 psi (450 MPa)
Ballistic performance
Bullet mass/type Velocity Energy
60 gr (4 g) HP 3,817 ft/s (1,163 m/s) 1,942 ft⋅lbf (2,633 J)
75 gr (5 g) HP 3,555 ft/s (1,084 m/s) 2,105 ft⋅lbf (2,854 J)
80 gr (5 g) SP 3,514 ft/s (1,071 m/s) 2,194 ft⋅lbf (2,975 J)
90 gr (6 g) SP 3,394 ft/s (1,034 m/s) 2,303 ft⋅lbf (3,122 J)
100 gr (6 g) HP 3,202 ft/s (976 m/s) 2,277 ft⋅lbf (3,087 J)
Source(s): Hodgdon [1]

Design

The .240 Weatherby Mag. is a proprietary cartridge used only in Weatherby rifles. This particular Weatherby case is unique: other than shape, it isn't physically based on other Weatherby cases, having the same rim diameter and a similar length to the .30-06. It utilizes the traditional Weatherby rounded double shoulder and a belted case with a length of 2.496in, significantly shorter than the 2.8in case of the .244 H&H Mag.[3]

Performance

In terms of velocity, the .240 Weatherby Magnum was once the fastest commercially produced 6 mm cartridge. There were several faster wildcat rounds available, but the .240 Wby. Mag. outclassed the 6 mm Remington and the newer .243 WSSM by about 150 ft/s (46 m/s).[4] However, the lightweight .243 WSSM 55gr Ballistic Silvertip now outpaces Weatherby's offerings according to some.[5] Loading data from Western Powders puts the .240 Wby. Mag. at over 4,000 ft/s (1,200 m/s) with a 62 grain Barnes bullet.[6]

While favoured by some varmint hunters, the .240 Wby. Mag. is not much liked by some reloaders because the case cannot be formed out of any other brass; one either has to buy Weatherby ammunition or reload used Weatherby cases which tend to be more expensive than those for more common cartridges. With heavier bullets the .240 Wby. Mag. makes for a good deer hunting cartridge, but it does tend to require a long (>23 inches (580 mm).) barrel in order to achieve peak performance.

Performance for 100 grain bullet from utilizing a factory 26" test barrel and a Nosler Partition bullet)
Muzzle100 yd200 yd300 yd400 yd500 yd
Trajectory 2.83.50-8.4-22.9
Energy (ft·lbf) 257621831844155012941073
Velocity (ft/s) 340631362882264224152199
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See also

References
  1. "Hodgdon Online Reloading Data". Archived from the original on 2007-11-16. Retrieved 2007-07-20.
  2. The .240 Weatherby Magnum by Chuck Hawks
  3. The .240 Weatherby Magnum by Chuck Hawks (subscription required)
  4. Compared: The .243 WSSM and .240 Wby. Mag. by Chuck Hawks (subscription required)
  5. "SBST243SS". Olin Corporation 190 Carondelet Suite 1530 Clayton, MO 63105. Archived from the original on 2014-10-13. Retrieved 2014-07-28.
  6. "Western Powders" (PDF).
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