The .257 Weatherby Magnum
By Chuck Hawks
The .257 Magnum is one of the early Weatherby calibers, designed in 1944. It is one of the most popular Weatherby calibers, combining very high velocity, flat trajectory, and tolerable recoil. It is reputed to have been Roy Weatherby's favorite cartridge.
Weatherby offers several factory loads for the .257 Mag. The lightest bullet available is an 87 grain Hornady Spire Point Bullet at 3825 fps, which is the varmint and predator load for the caliber. For medium game such as deer and the smaller antelope species at long range there is a 100 grain Hornady Spire Point bullet at 3602 fps and a 115 grain Nosler Ballistic Tip bullet at 3400 fps. For woods and brush country hunters there is a 117 grain Hornady Round Nose bullet at 3402 fps. For larger or tougher game Weatherby offers a 115 grain Barnes X-Bullet spitzer at 3400 fps, and a 120 grain Nosler Partition spitzer bullet at 3305 fps.
As usual with Weatherby Magnum cartridges, reloaders will have difficulty exceeding the velocities of Weatherby factory loaded ammunition, but the other advantages of reloading (tuned loads and economy, for instance) still apply.
Here are some specifications of interest to reloaders: bullet diameter .257", maximum COL 3.17", maximum case length 2.549", MAP 53,500 cup.
There is a good selection of bullets available in .25 caliber. These range from 60 to 120 grains, although it is hard to see much point to bullets lighter than 85 grains in a cartridge with the case capacity of the .257 Wby. For hunting CXP2 class game, bullets from 100 to 120 grains are called for.
Weatherby rifles made in Germany prior to 1972 usually have 1 turn in 12" rifling and will not stabilize most bullets over 100 grains. Later Weatherby .257 rifles have 1-10" rifling and are fine with the long 120 grain bullets.
Slow burning rifle powders are generally recommended for the .257 Wby. Examples of suitable powders include AA-3100, H870, H4831, IMR 4831, IMR 7828, RL-22 and RL-25. RL-25 and IMR 7828 are favored for the heavier 115-120 grain bullets.
The Hornady Handbook of Cartridge Reloading, Sixth Edition shows that their 100 grain Spire Point bullet can be driven at a MV of 3000 fps by 67.2 grains of RL-25 powder, and lists a maximum load using 75.0 grains of RL-25 powder with the same bullet that achieves a MV of 3500 fps. Weatherby brass and Federal 215 primers were used for these loads, which were tested in a Weatherby rifle with a 26" barrel.
The fifth edition of the Noser Reloading Guide shows that behind their 115 grain bullets 65.0 grains of IMR 7828 gives a MV of 3237 fps. The top load listed for their 115 grain bullets gives a MV of 3433 fps with 69.0 grains of IMR 7828 powder.
For the 120 grain Nosler Partition bullet the starting load is 65.0 grains of IMR 7828 for a MV of 3206 fps, and the top MV is 3402 fps in front of a maximum load of 69.0 grains of IMR 7828. Weatherby brass and Federal 215 primers were used for all of these Nosler loads, which were tested in a 26" barrel.
Note: A full length article about the .257 Wby. Mag. can be found on the Rifle Cartridge Page.
Copyright 2004 by Chuck Hawks. All rights reserved.