The 7mm Weatherby Magnum
By Chuck Hawks
The 7mm Weatherby Magnum has been overshadowed (at least in sales) by the later 7mm Remington Magnum. But it was the 7mm Weatherby that actually got there "furstest with the mostest," being introduced in 1944. It took Remington well over a decade to catch up with Roy Weatherby's innovative 7mm Magnum.
Weatherby's Big 7 is based a shortened .300 H&H Magnum case with the usual double radius Weatherby shoulder. This is the same basic case used for the .270 Wby. Mag. and .257 Wby. Mag. It is not the case used for the .300 Wby. Magnum, which is based on an "improved" full length .300 H&H case.
As a point of interest, in his later years Roy Weatherby admitted that in his own testing the double radius shoulder had shown no advantage over a normal, fairly sharp, angled shoulder. But it was a successful marketing tool in the early years, when it was claimed to improve gas flow in the case and increase cartridge efficiency.
The 7mm Weatherby has slightly more powder capacity than the later 7mm Rem. Mag., and consequently slightly greater performance with maximum loads. Its sales lag behind Remington's Big 7 due to the relatively high cost of Weatherby rifles and ammunition. For the fan of Weatherby's innovative rifles, however, the 7mm Wby. Mag. remains one of the best all-around Weatherby cartridges. No less an authority than Jack O'Connor believed it to be the best of all the 7mm Magnum cartridges, including wildcats.
Factory loaded ammunition is available from Federal, Hornady, Weatherby, and Norma of Sweden (who also loads Weatherby brand ammunition). Federal offers three different bullets, all of 160 grain weight. Hornady offers their 154 grain and 175 grain bullets in their factory loads, and Weatherby offers 139, 140, 150, 154, 160, and 175 grain bullets. This might represent an embarrassment of riches, as there is not much that cannot be handled by a good 150 to 160 grain bullet in any 7mm Magnum caliber.
The Weatherby factory load using a 150 grain Barnes X-bullet starts with a muzzle velocity of 3100 fps and muzzle energy of 3200 ft. lbs. At 300 yards that bullet is still traveling 2527 fps and carrying 2127 ft. lbs. of energy. The factory trajectory figures for that load fired from a scoped rifle shows the bullet to be +3.3" at 100 yards, +4" at 200 yards, 0 at 300 yards, and -9.4" at 400 yards. This makes the 7mm Weatherby about a 350 yard big game cartridge with this excellent all-around bullet.
The Hornady factory load using a 154 grain Interlock bullet starts with a MV of 3200 fps and a ME of 3501 ft. lbs. At 300 yards that bullet is traveling at 2546 fps with 2216 ft. lbs. of energy. The trajectory of that bullet is virtually identical to that of the 150 grain X-Bullet (above). This same bullet is also available in Weatherby brand ammunition (at a MV of 3260 fps). This is perhaps the best bullet for game of less than about 350 pounds in the caliber, without seriously compromising performance should one get a chance at a substantially larger animal like an elk.
The Federal factory load using a 160 grain Nosler Partition bullet starts at 3050 fps with 3305 ft. lbs. of ME. At 300 yards it is traveling at 2470 fps and carrying 2165 ft. lbs. of energy. The improved BC of the longer 160 grain bullet makes up for the difference in velocity, and the trajectory is within 0.1-0.2" of that quoted above for the 150 grain X-Bullet. The 7mm Wby. remains about a 350 yard elk, kudu, eland, and moose cartridge. This is probably the best factory loaded bullet for really big or dangerous animals, and it is offered in Weatherby brand ammunition (at a MV of 3200 fps) as well as by Federal.
The handloader has a greater selection of bullet weights and styles, but it is hard to see what advantage they offer over the 150-160 grain bullets in this caliber. Good reloads can about equal the velocity of the factory loads above, but not appreciably exceed them. The 7mm Weatherby is standardized at 65,000 psi maximum mean pressure by the SAAMI, and that is also the practical maximum for the handloader. The third edition of the Hornady Handbook of Cartridge Reloading shows that their 154 grain spire point bullet can be driven to a MV of 2800 fps by 65.8 grains of H4831 powder, and a MV of 3200 fps by 71.9 grains of H4831.
Comparing the 7mm Weatherby and 7mm Remington Magnums reveals an advantage of about 0-100 fps in favor of the Weatherby Magnum, depending on the bullet weight, if both are measured in 24" barrels. Current production Weatherby Mark V rifles come with 26" barrels, which gives the Weatherby cartridge an advantage.
As one might assume, there is also not much difference in recoil energy (assuming equivalent loads) between the two popular 7mm Magnum calibers. My Rifle Recoil table shows 20.3 ft. lbs. of recoil energy for the 7mm Wby. shooting the 154 grain bullet from a 9.5 pound Mk. V rifle. The Weatherby stock, designed for magnum recoil, might actually give the Weatherby Magnum an advantage in terms of perceived recoil. In short, there is really no reason for anyone considering a 7mm Magnum, or who needs an extremely capable all-around rifle and happens to admire Weatherbys, to refrain from purchasing a Mark V in 7mm Weatherby Magnum caliber.
Copyright 2002, 2012 by Chuck Hawks. All rights reserved.