The .270 Weatherby Magnum
By Chuck Hawks
The .270 Magnum was the first case designed by Roy Weatherby, back in 1943. 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). A year later Weatherby necked his new .270 Magnum case down to accept .257" bullets and up to accept .284" (7mm) bullets, thereby creating the .257 and 7mm Weatherby Magnums. All three of these ultra-long range big game cartridges will work through a standard (.30-06) length action. No less an authority than Ed Weatherby, President of Weatherby, Inc., has gone on record saying that the .270 Wby. is his favorite caliber.
For the Weatherby fan, .270 Wby. Mag. has the sterling virtue of being the lightest Weatherby caliber suitable for hunting all North American big game. This magnum .270 requires a 26" barrel to get the full velocity, and thus energy, from the cartridge. All current production Weatherby Mark V rifles in .270 Wby. Mags are so equiped. From normal length barrels, the .270 Weatherby Magnum delivers more increase in muzzle blast and recoil than it does velocity. Stick with the regular .270 Winchester if you want a rifle with a 22" barrel.
Recoil is the problem with most magnum rifles, and the .270 Weatherby is no exception. The figure is 26.6 ft. lbs. for an 8.5 pound .270 Wby. Mag. rifle shooting the 150 grain factory load. This is well over the 20 ft. lb. maximum most shooters can tolerate. However, it is not particularly extreme compared to other flat shooting magnum cartridges firing 150 grain bullets in 8.5 pound rifles. The figure for the 7mm Rem. Mag. is 22.6 ft. lbs; for the 7mm Ultra Mag, 37.4 ft. lb.; for most of the standard length .300 Magnums, about 27.5 ft. lbs.
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 a 20 yard advantage in range over the standard .270 Win. Whether the increased muzzle blast, recoil, and rifle length and weight are worth it is for the consumer to decide.
Where the Weatherby caliber really shines is with the 150 grain bullet. At 100 yards this load developes 3,055 ft. lbs of energy, making it suitable for any North American big game, including the great bears, at this range. For comparison, the .270 Win. developes 2,900 ft. lbs. at the muzzle, and around 2,400 ft. lbs. at 100 yards. At 400 yards the 150 grain .270 Weatherby bullet is still packing 1,981 ft. lbs. of energy, compared to about 1,400 ft. lbs for the best .270 Winchester load. In fact, the 150 grain bullet from the .270 Weatherby Magnum hits harder at all ranges than the the best bullet (which happens to also be 150 grains) from the very popular 7mm Rem. Mag.
The trajectory of the 130, 140, and 150 grain bullets are nearly the same. The Weatherby factory load with a 150 grain Nosler Partition bullet looks like this (assuming a line of sight 1.5 inches above the bore): +3" at 100 yards, +3.7" at 200 yards, 0" at 300 yards, -8" at 400 yards. This is a flatter trajectory than any load for the .264 Win. Mag, the 7mm Rem. Mag. or even the 7mm Wby. Mag.
Reloaders can save money but not exceed the performance of the factory loads. 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 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. 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.
Copyright 2001, 2012 by Chuck Hawks. All rights reserved.