7mm Weatherby Magnum

History

It was developed among the first line of Weatherby cartridges back in the early 1940s by Roy Weatherby. As with other Weatherby Magnum cartridges, the 7mm Wby Mag design is based on the .300 Holland & Holland Magnum case. It is necked down to 7mm (.284) and features the trademark double radius shoulder. The case was blown out to eliminate the taper and shortened to feed from a standard length action like the .257 Wby Mag and the .270 Wby Mag.

The 7mm Weatherby Magnum did not get a lot of exposure until the early part of the 1950s when the Weatherby rifles became more available. The more popular 7mm Remington Magnum, introduced in 1962, has similar ballistics when compared to the 7mm Weatherby. However, being introduced 18 years earlier, the 7mm Weatherby Magnum due to the case design delivers a slight edge over the more popular 7mm Rem Mag in terms of ballistics. But since it is fed from a similar action length, the Remington was available in cheaper more plentiful rifles giving it a significant boost in popularity that continues to this day.

Weatherby's early 7mm rifles were manufactured with 1:12" barrels, which were too slow to stabilize the heavier bullets. Once the 7mm Rem Mag was introduced, manufactured with 1:9 1/4" barrels, Roy Weatherby decided to modify the twist for a 1:10.

Sporting use

The 7mm Weatherby Magnum is a very adequate cartridge for hunting medium to large-sized deer such as mule deer, wapiti and moose, up to long ranges due to its plain trajectory with bullets of different weights and due to the high ballistic coefficient the 7mm bullets are praised for. However, with adequately constructed bullets, the 7mm Wby Mag may be used for hunting larger game, including the great bears and the American bison.

As with other belted magnum cartridges, recoil is significant, due to the high pressures that are characteristic of Weatherby Magnum, though not as heavy as larger-caliber magnums such as the .300 Weatherby Magnum. Care must be taken to confirm what twist rate was used, as the earlier West German 7mm Weatherbys used a 1-in-12 twist vs the faster 1-in-10 twist for those of later manufacture. The 1x12 twist rifles will not stabilize bullets over 150 grains, while the 1x10 twist rifles will stabilize bullets weighing up to 175 grains.

References

References

1. Speer Reloading Manual Rifle & Pistol Number 13
2. Bullets, Speer. (2009). "Speer Bullets Reloading Manual #14". Speer.
3. (May 29, 2012). "Remington's Big Seven".