There are big magnum cartridges, and then there are big magnum cartridges. Weatherby has—since the mid 1940s—been associated with velocity. Considering the limits of smokeless powder developments in that era—as we certainly didn’t have the slow burning powders like H1000, Retumbo and the like—Roy Weatherby did alright. His main line of cartridges were based on the .300 and .375 H&H Magnums, shortened to varying lengths, but in 1953 Roy released his behemoth .378 Weatherby Magnum, which will drive a 300-grain bullet to 3,000 fps. Though the .378 Weatherby has a belt in the style of the H&H case, it has no parent case and is much larger in body than those Holland cases. I own a .378 Weatherby Magnum—a Ruger No. 1 Tropical, re-chambered from .375 H&H Magnum, which belonged to the late PH Jay Carlson—and it has a very formidable recoil level the shooter doesn’t soon forget.
In the late 1950s, the U.S. Army had put out a request for a .30-caliber cartridge which could break the 6,000 fps mark. Roy Weatherby answered the call by taking his behemoth .378 Weatherby Magnum case and necking it down to hold .30-caliber bullets, resulting in the .30-378 Weatherby Magnum; he did, in fact, break that 6,000 fps mark with this cartridge. The case has a rim diameter of 0.579 inches (compared to the H&H case with a 0.532-inch rim), and an overall length of 2.913 inches. The double radius shoulder ends in a neck measuring 0.344 inches—well over the usually desired one-caliber in length—and the overall cartridge length is limited to 3.648 inches, so the case should be at home in any magnum-length receiver.
The cartridge would sit in the shadows for decades, until Roy’s son Ed Weatherby was convinced by gunwriter Layne Simpson to bring the design to the masses. In 1996, Weatherby did just that, and the .30-378 Weatherby Magnum was available to the shooting public. While the attraction to the hunting community was, and is, obvious, the long-range target community immediately started breaking and setting some serious accuracy records with the big cartridge. Target shooter Earl Chronister printed a ten-shot group at 1,000 yards which measured 4.3 inches with this cartridge, which was unbelievable at the time.
On the hunting end of things, the .30-378 Weatherby Magnum exceeds the velocities of the .300 Weatherby Magnum by roughly 200 fps, driving a 180-grain bullet to over 3,400 fps (in handloaded form), generating more than 4,000 ft-lbs. Weatherby is the dominant source of factory-loaded ammunition, and at the time of this writing, they list seven different choices of projectile. Included in the mix are the Barnes TTSX, Swift Scirocco II, Nosler Ballistic Tip and Hornady Interlock (all at 180 grains), the 195-grain Hammer monometal bullet, the 200-grain Nosler Partition and the 220-grain Hornady ELD-X. The 180s are cruising at right around 3,300 fps, and the 200-grainers are travelling at 3,150 fps. One interesting point I’d like to make about this cartridge, considering the velocities generated, is that if ever there was a case to be made for the use of premium bullets, it’s the .30-378 Mag. I love the Nosler Ballistic Tip and Hornady Interlock, and have used both in varying situations around the globe, but I wouldn’t describe either as a particularly tough bullet. If the shot with the .30-378 Weatherby Magnum were far enough for the bullet to slow down considerably, that’s one thing, but either of those bullets used at an impact velocity of over 3,000 fps could result in a mess. When I load for a .30-378 Weatherby, I always reach for either a monometal bullet like the Barnes TTSX or LRX, or one of the bonded core bullets like the Swift Scirocco II, Nosler AccuBond, Federal Trophy Bonded Tip or the like. Both of those designs mitigate premature bullet breakup and excessive meat damage.
Those velocities will also directly translate to a vicious recoil level, especially if the rifle stock doesn’t fit the shooter perfectly. I detest muzzle brakes, as my ears have taken a beating over the years of shooting, hunting and playing in rock bands, but this is one cartridge I’d definitely want a good brake for, as well as a thick, pliable recoil pad. Based on the powder volume (the .30-378 can easily burn over 100 grains of powder) I also like to see a 26-inch barrel to burn all that propellant.
What is the .30-378 Weatherby Magnum for? Is it a target cartridge? Well, yes and no. It seems rather extreme in this day and age to use something of this volume for long-range target shooting, considering how well the lighter cartridges perform. Is it the ultimate hunting round? Well, it can be a good hunting round, but the owner needs to realize that closer shots can be messy, and there might be better choices for a “woods rifle”. The .30-378 is suitable for all North American game, when mated with a proper projectile, and will handle the vast majority of African species, save the heavyweight, thick-skinned dangerous species. This all comes at a price of enhanced report, recoil and wear on the rifle—both in bolt thrust and throat erosion. That aside, if you like having the biggest and baddest cartridge on the block, the .30-378 Weatherby Magnum is the fastest .30-caliber on the market, and it will certainly grab the attention of your friends and hunting partners.
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