The .240 Weatherby Magnum
By Chuck Hawks
The .240 Weatherby Magnum was introduced in 1968, and it was the last Weatherby caliber introduced while Roy Weatherby was still alive. The .240 Weatherby case is unique. It is a standard length and diameter cartridge with a .473" rim diameter, the same as a 30-06, and it will work through any standard length action. Like all Weatherby cartridges, it is a belted case with a double radius shoulder. It is a very cute magnum cartridge, with a powder capacity much like that of the 6mm-06 or 6mm-284 wildcats. Norma manufactures Weatherby brand ammunition. The .240 has a SAAMI maximum average pressure of 53,500 cup.
Weatherby touts the .240 as a combination long range varmint and big game cartridge. It certainly has the ballistics to back up those claims, but for a varmint rifle it burns an awful lot of powder, kicks pretty hard, is quite noisy, and heats up its barrel very quickly. Burning so much powder behind such a small diameter bullet generates a lot of heat that dissipates rather slowly, so to prevent burning out the throat of a .240 rifle the barrel should be allowed to cool between shot strings (which should be kept short). While these limitations are perfectly acceptable for a big game rifle, they do not an ideal varmint rifle make.
The .240 Weatherby is the highest velocity commercially produced 6mm cartridge. It will drive a 100 grain bullet about 150 fps faster than the 6mm Remington from a 26" barrel, less from a 24" barrel. Of course, if the 6mm is measured in a 24" barrel and the .240 in a 26" barrel, which is the case with factory load ballistics, the difference goes up to about 300 fps.
Bob Hagel, a gun writer whose opinion I respect, called the .240 Weatherby "just a little more of the same thing" when comparing it to the 6mm Rem. He went on to relate that he had killed a number of deer-size animals with both, and "in nearly all instances performance was good."
.240 Weatherby factory ammunition is offered only by Weatherby, and like all Weatherby factory loaded ammo it is expensive. Bullet weights of 87, 90, 95, and 100 grains are currently offered. The .240 case is unique and cannot be formed from any other existing case, which has limited the cartridge's popularity with reloaders. Never the less it is an exceedingly effective long range cartridge, and its approximately 14.5 ft. lbs. of recoil can be managed by most shooters.
Current Weatherby figures claim a muzzle velocity of 3406 fps for a 100 grain spitzer bullet from a 26" test barrel. At 100 yards the velocity is given as 3136 fps and the energy as 2183 ft. lbs. And at 400 yards the velocity is still 2415 fps and the remaining energy an impressive 1294 ft. lbs.
The trajectory of that load (using a Nosler Partition bullet) is as follows: +2.8" at 100 yards, +3.5" at 200 yards, 0 at 300 yards, and -8.4" at 400 yards. That will do for deer to about 350 yards, and qualifies the .240 Weatherby as a true ultra-long range rifle.
At one time Weatherby supplied Mark V rifles for the .240 with both 24" and 26" barrels, but the latest reference I have at hand (a 2002 Weatherby Catalog) shows that the .240 is only available with a 24" barrel. It is still a very flat shooting caliber but it will not achieve the advertised ballistics in the shorter barrel.
Handloaders have a wide selection of bullets from which to choose, since the .240 Weatherby uses regular .243" bullets. The most common bullet weights are 70, 75, 80, 85, 90, 95, 100, and 105 grains.
For examples of the velocities that can be achieved in a rifle with a 24" barrel, I took the following loads from the Speer Reloading Manual No. 13. The good folks at Speer chronographed their loads in a Weatherby Mark V hunting rifle with a 24" barrel, using Weatherby brass and CCI 250 primers.
With the Speer 80 grain varmint bullet in front of 50.0 grains of IMR 4831 powder the MV was 3327 fps; in front of 54.0 grains of IMR 4831 the velocity rose to 3583 fps. Using a 100-105 grain bullet and 45.0 grains of W760 powder the MV was 2922 fps. A maximum charge of 49.0 grains of W760 gave a MV of 3206 fps. (Note that this is exactly 200 fps less velocity than claimed for the factory load with the 100 grain bullet.)
Using figures from the Speer Reloading Manual a 100 grain Grand Slam bullet that starts with a MV of 3200 fps from a 24" Weatherby rifle barrel will be traveling at 2914 fps at 100 yards, 2645 fps at 200 yards, 2392 fps at 300 yards, and 2153 fps at 400 yards. The remaining energy at 400 yards is a satisfying 1029 ft. lbs. The trajectory for that load looks like this: +2.5" at 100 yards, +2.4" at 200 yards, -2.6" at 300 yards, and -13.4" at 400 yards. The maximum point blank range (+/- 3") is 305 yards.
Copyright 2002, 2012 by Chuck Hawks. All rights reserved.