The .338-378 Weatherby Magnum

By Chuck Hawks

As the name implies, Weatherby's ultimate .338 is based on a necked-down .378 Weatherby Magnum case. Both Elmer Keith and Roy Weatherby experimented with necking-down the .378 case to accept .338" diameter bullets, but these experiments remained wildcats for almost 30 years. Around 1999, long after the death of both men, the Weatherby company finally introduced the .338-378 Weatherby Magnum as a commercial cartridge.

This huge belted case was inspired by the .416 Rigby case and incorporates the signature double radius Weatherby shoulder. It has a .579" rim diameter, a .582" head diameter just forward of the belt, a .561" shoulder diameter, and a maximum case length of 2.913". The overall cartridge length is 3.763".

Shooters preferring an ultra-powerful medium bore Weatherby rifle that shoots .338" diameter bullets instead of .375" diameter bullets can purchase the TRM, Accumark, or Synthetic models in .338-378 Weatherby caliber. All Weatherby rifles in .338-378 come standard with 28" barrels and include the company's Accubrake muzzle brake. This device is removable for hunting and where required, but really is necessary to help moderate the viscous recoil of the cartridge. Because of the severe muzzle blast, the shooter must always wear maximum hearing protection when using the Accubrake.

The .338-378 is a caliber useful for killing large, thin-skinned dangerous game all over the world, such as the great bears, jaguar, lion, and tiger. These beasts should be shot at the usual dangerous game ranges of 50-150 yards. The .338-378 has the power to anchor such game with solid hits, which is what you want from a dangerous game rifle. The .338-378 also has the power and sectional density (with appropriate bullets) to handle the bovine species of thick-skinned dangerous game such as Asian wild water buffalo, North American bison, and African Cape buffalo (where legal). Never, under any circumstances, shoot at a dangerous game animal over 200 yards away with anything! This isn't a matter of trajectory, it is a matter of energy on target and the possibility of human error.

Factory loaded ammunition is available from Weatherby with 200 grain, 225 grain, and 250 grain spitzer bullets. The 200 grain offering is a Nosler Ballistic Tip bullet at a MV of 3350 fps and ME of 4983 ft. lbs. Weatherby ballistic tables show the following trajectory for this load: +2.8" at 100 yards, +3.5" at 200 yards, 0 at 300 yards, -8.4" at 400 yards, and -22.9" at 500 yards.

The 225 grain number is a Barnes X-Bullet at a MV of 3180 fps and ME of 5052 ft. lbs. The 400 yard figures are 2410 fps and 2902 ft. lbs., and at 500 yards the sleek Barnes X-Bullet is still rolling along at 2238 fps and carrying 2501 ft. lbs. of kinetic energy. For comparison, that is about the same energy a 200 grain .300 Win. Mag. bullet carries at 200 yards. The ballistic tables show the following trajectory for this load: +3.1" at 100 yards, +3.8" at 200 yards, 0 at 300 yards, -8.9" at 400 yards, and -24" at 500 yards.

The 250 grain bullet is the popular Nosler Partition. The MV of this load is 3060 fps and the ME is 5197 ft. lbs. The 400 yard figures are 2297 fps and 2927 ft. lbs. Weather ballistics are as follows: +3.5" at 100 yards, +4.2" at 200 yards, 0 at 300 yards, -9.8" at 400 yards, and -26.4" at 500 yards.

Handloaders can come pretty close to these velocities. The fifth edition of the Hornady Handbook of Cartridge Reloading shows that 85.8 grains of H1000 powder behind a 250 grain bullet yields a MV of 2500 fps, and 107.8 grains of H1000 pushes the MV to 3000 fps. The maximum H1000 load in the Nosler Reloading Guide is very similar. The "Rifle Trajectory Table" shows that a 250 grain bullet with a BC of .473 at 3000 fps has a maximum point blank range (+/- 3") of 297 yards. The Optimum Game Weight Formula shows that a 250 grain .338 bullet at a MV of 3000 fps has an optimum game weight of 1100 pounds at 400 yards.

These nearly otherworldly ballistics make it evident that the long range killing power of the .338-378 exceeds the skill of all but the tiniest minority of shooters. So, unfortunately, does the recoil. The "Rifle Recoil Table" shows that our handload driving a 250 grain bullet at a MV of 3000 fps generates 46.5 ft. lbs. of recoil energy in a 9.5 pound rifle. No one should buy such a rifle without first firing a few groups at the range to insure that they can handle it.

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Copyright 2003, 2012 by Chuck Hawks. All rights reserved.