The .340 Weatherby Mag.
By Chuck Hawks
The .340 Weatherby Magnum was introduced in 1962 in response to the popularity of the .338 Winchester Magnum. It is based on the .300 Weatherby case necked up to accept .338" bullets. Since the .338 Win. Mag. will kill anything that should be hunted with a .338 rifle, what you are buying in the .340 is a somewhat flatter trajectory. It is, at least, a better balanced cartridge than the other .338 Super Mags (.338 RUM, .338 Lapua, .338-378 Wby., etc.)
A-Square, Federal, and Weatherby offer factory loads for the .340. The Weatherby factory loads offer the greatest variety of bullet weights, including 200 grain, 210 grain, 225 grain, and 250 grain. The 250 grain Pointed Expanding bullet has a MV of 2,963 fps and a ME of 4,873 ft. lbs.
The .340 Weatherby is just about the biggest case that makes any sense for a bullet of .338" diameter. If you must have a .338 super mag, the .340 Wby. is the way to go. Here are some other specifications important to reloaders: Maximum COL 3.675", Maximum case length 2.825", MAP 53,500 cup.
Because Weatherby factory ammunition is loaded to maximum pressure, reloaders will have difficulty duplicating the published Weatherby ballistics. On the other hand, the extensive array of .338" bullets, strong Weatherby brass, the high price of .340 factory loads, and the possibility of loading the .340 down to, say, .338 Win. Mag. levels to help control the .340's fierce recoil make the .340 a prime candidate for reloading.
As with other .338 caliber cartridges, bullets ranging from 200-250 grains are the most popular. Due to the .340 Weatherby's big case, slow burning powders such as H4831, IMR 4831, IMR 7828, RL-19, RL-22, RL-25, and Win WMR are most suitable.
The sixth edition of the Hornady Handbook of Cartridge Reloading shows that 79.1 grains of RL-19 powder behind a 200 grain bullet gives a MV of 2800 fps, while a maximum load of 89.3 grains of the same powder gives a MV of 3200 fps.
Using 225 grain bullets, the Hornady Handbook shows that 78.6 grains of H4831 is good for a MV of 2700 fps, and a maximum charge of 84.8 grains of the same powder achieves a MV of 3000 fps. These Hornady loads were tested in the 26" barrel of a Weatherby Mark V rifle and used Weatherby Brass and Federal 215 primers.
The fifth edition of the Nosler Reloading Guide shows muzzle velocities of 2648 fps with their 250 grain bullets and 82.0 grains of IMR 7828 powder. 86.0 grains of IMR 7828 drove the 250 grain Nosler bullets at a MV of 2818 fps. These Nosler loads used Weatherby brass and Federal 215 primers, and were tested in a 26" barrel.
Note: A more extensive article about the .340 Wby. Mag. can be found on the Rifle Cartridge Page.
Copyright 2004, 2016 by Chuck Hawks. All rights reserved.