The .270 Weatherby Magnum
By Chuck Hawks
The .270 Magnum was the first case designed by Roy Weatherby, back in 1943, and it remains one of the most popular Weatherby calibers. It is based on a shortened and necked down .300 H&H Mag. case with a sharp double radius shoulder (common to all Weatherby cartridges). Given the popularity of the .270 Winchester, it is surprising that the .270 Wby. remained the only commercial .270 Magnum for so long. The introduction of the .270 WSM, a cartridge inbetween the performance of the .270 Win. and the .270 Wby. Magnum gives shooters three .270s from which to choose. However, the Weatherby version remains the performance champion by a substantial margin, without the potential feeding problems inherent in the WSM case.
Weatherby factory loads drive a 100 grain bullet at 3,760 fps, a 130 grain bullet at 3,375 fps, a 140 grain bullet at 3,250-3,300 fps, and a 150 grain bullet at 3,245 fps. The 100 grain bullet is strictly for varmints, and this big .270 burns too much powder to be a reasonable varmint rifle. The 130 and 140 grain bullets are fine for antelope, deer, sheep, and goats. The 150 grain bullet would seem to be the best bullet for large game.
The "Rifle Trajectory Table" shows that when the 130 grain bullet is zeroed in such a way as to keep to keep the maximum rise and fall within plus or minus three inches from the line of sight, the .270 Wby. Mag. is about a 326 yard deer rifle. This gives it an advantage over the newer .270 WSM.
Reloaders will find it difficult to exceed the performance of the factory loads. The slow burning rifle powders are the best choice. Powders such as IMR 4350 and H4350 are the fastest burning powders suitable for this cartridge, and RL-22, RL-25, and IMR 7828 are often recommended.
Here are some important specifications for the .270 Weatherby: bullet diameter .277", maximum COL 3.295", maximum case length 2.549", MAP 53,500 cup.
In the fifth edition of the Nosler Reloading Guide it shows that their 130 grain bullets can be driven to a MV of 3221 fps with 67.0 grains of RL19, and up to 3414 fps with 71.0 grains of the same powder.
With the 140 grain Nosler bullets 67.0 grains of IMR 7828 gave a MV of 3053 fps, and 71.0 grains of IMR 7828 gave a MV of 3260 fps.
With 150 grain Nosler bullets 66.5 grains of IMR 7828 gave a MV of 3033 fps, and 70.5 grains gave a MV of 3207 fps.
The heavy 160 grain Partition semi-spitzer can be driven to a MV of 2931 fps with 66.0 grains of IMR 7828, or 3098 fps with 70.0 grains of the same powder. All of these Nosler loads were developed using Weatherby cases and Federal 215 primers, and tested in a 26" barrel.
The reloader with a .270 Wby. Mag. rifle has about a 200 fps advantage over a reloader with a .270 WSM rifle when both are using 150 grain bullets. Clearly, for heavy animals at long range, the .270 Weatherby is a superior choice.
Note: A full length article about the .270 Weatherby Magnum can be found on the Rifle Cartridge Page.
Copyright 2004, 2016 by Chuck Hawks. All rights reserved.