The .458 Winchester Magnum
By Chuck Hawks
The .458 Winchester Magnum is the most popular "elephant rifle" cartridge in the world. It was introduced in 1956, the first of the original series of three Winchester belted magnum cartridges for standard length actions. (The other two were the .264 Mag. and the .338 Mag.) It quickly established itself as one of the premier cartridges for thick-skinned dangerous game (elephant, rhino, and buffalo).
The .458 is based on a straight, standard length belted case with moderate body taper that measures 2.5" in length. It has the standard .532" magnum rim diameter, which is also the diameter of the case at the belt. The cartridge is 3.34" in overall length. The SAAMI maximum average pressure is 53,000 cup, or 62,000 psi by the piezo transducer method.
The .458 appeared in a special version of the Model 70 bolt action rifle named the "African." I have heard that its immediate acceptance and popularity surprised even Winchester.
It was introduced at a time when air travel was beginning to allow affluent middle-class hunters from North America to embark on African safaris that only ten years earlier had been prohibitively expensive and time-consuming. In 1956, the year the .458 Mag. appeared, the introduction of the Douglas DC-7C airliner made possible affordable nonstop Trans-Atlantic air service in both directions. It was followed by the Lockheed Starliner, which entered Trans-Atlantic service in 1957. The Boeing 707 jetliner entered service in 1958, and the first Douglas commercial jetliner, the DC-8, entered service in 1959. The .458 Win. Mag. turned out to be the right cartridge at the right time.
The performance of the .458 Win. Mag. was based very closely on that of the British .450 Nitro Express and its popular successor the .470 Nitro Express. The .470 Nitro Express had became the most popular of all the British elephant rifle cartridges. As originally loaded with cordite (British smokeless) powder, it drove a 500 grain bullet at a MV of 2,125 fps for a ME of 5,030 ft. lbs. Performance on thick-skinned dangerous game was, and is, excellent.
This was the baseline the .458 Win. was designed to match, and Winchester's original .458 factory loads offfered exactly the same velocity and energy. Recoil from full power .458 Magnum loads is terrific, of course; about 62 ft. lbs. of recoil energy from a 500 grain bullet at 2,100 fps in a 9 pound rifle.
The main drawback to the Nitro Express cartridges is their excessive length. They were designed for break action double rifles, not repeaters. And new double rifles are prohibitively expensive for all but the very rich, which is where the .458 Win. Mag. comes in.
The .458 works through standard length bolt action rifles, and duplicates the traditional ballistics of the .470 N.E. Several manufacturers chamber their bolt action rifles for the .458 Magnum, including Beretta, CZ, Dakota, Remington, Ruger, Savage, Weatherby, and Winchester. It is also chambered in modern single shots, like the elegant Dakota 10 and Ruger No. 1H Tropical Rifles, and most double rifles are now available in .458 Mag. as well as the traditional British Nitro Express cartridges.
In the United States .458 Mag. factory loads are available from A-Square, Federal, Hornady, Norma, Remington, Speer and Winchester. Bullet weights run from 350-510 grains in both expanding and non-expanding (solid) types. .458 Mag. ammunition is manufactured and distributed world wide.
Federal offers a very good selection of .458 factory loads in their Premium Safari line, which can be taken as representative. These include a 350 grain soft point bullet (SD .238) at a MV of 2,470 fps and a ME of 4,740 ft. lbs. The figures at 100 yards are 1,990 fps and 3,065 ft. lbs. This load is primarily for hunters wishing to use their .458's on large North American game.
Another load uses a 400 grain Trophy Bonded Bear Claw (controlled expansion) bullet at a MV of 2,380 fps and a ME of 5,030 ft. lbs. That ought to stop the biggest Alaskan brown bear that ever lived.
Federal's line also includes a couple of 500 grain controlled expansion type bullets, and a 500 grain solid. All of these are loaded to a MV of 2,090 fps and a ME of 4,850 ft. lbs. The 100 yard figures are 1,870 fps and 3,880 ft. lbs. The solid is the traditional choice for breaking down thick-skinned dangerous game like elephant, rhino, and Cape buffalo.
The 510 grain soft point bullet, a traditional load for the .458, has a MV of 2,090 fps and a ME of 4,895 ft. lbs. The figures at 100 yards are 1,820 fps and 3,730 ft. lbs. This load has always been regarded as a "stopper" for thin-skinned dangerous game like lion and tiger, or heart/lung shots on buffalo.
None of the .458 Mag. factory loads are suited to long range shooting. Typical trajectory for a 500-510 grain factory load zeroed at 100 yards shows an 8.5" to 9" drop at 200 yards. Zero that load to hit 3" high at 100 yards and the maximum point blank range (MPBR) +/- 3" is extended to about 200 yards. See the "Rifle Trajectory Table" for more information.
Reloaders have their choice of 300, 350, 400, 450, and 500 grain .458" bullets in hollow point, soft point, premium controlled expansion, and solid (full metal jacket) types. Hodgdon 2002 reloading data shows that 80.0 grains of H4895 powder behind a 350 grain Speer Flat-SP bullet gave a MV of 2496 fps at a MAP of 38,700 cup. 77.0 grains of H4895 powder behind a 400 grain Swift A-Frame FP bullet gave a MV of 2349 fps at a MAP of 42,500 cup. 74.0 grains of H4895 powder behind a 500 grain Hornady RN bullet gave a MV of 2161 fps at a MAP of 50,300 cup. All of these Hodgdon loads used Winchester cases and CCI-250 primers, and were chronographed in a 24" barrel.
In recent years, .45-70 loads for strong single shot rifles have been devised that tread on the heels of the lighter .458 Magnum loads. Here is a reduced .458 Mag. load that I use, taken from the sixth edition of the Hornady Handbook of Cartridge Reloading, that offers .45-70 ballistics in a .458 Mag. case. This is a good load for the rifle range and for hunting medium size (CXP2) North American game: 38.9 grains of IMR 4198 powder behind a Hornady 300 grain JHP bullet for a MV of 1900 fps. This is a fun load to shoot in a .458, as the recoil is only about 18.5 ft. lbs. in a 9 pound rifle.
For large game like elk (CXP3), try a 350 grain RN bullet in front of 51.6 grains of IMR 4198 powder for a MV of 2100 fps. This raises the recoil ante to about 31.2 ft. lbs. in a 9 pound rifle; heavy, but still only about half that of full power loads using 500 grain bullets. That load has a MPBR of 189 yards (+/- 3") when zeroed to hit 3" high at 100 yards. Hornady used Winchester cases and WLRM primers for these loads, which were chronographed from the 24" barrel of a Ruger M-77 rifle. Performance from the 24" barrel of my Safari grade Browning .458 is similar. The .458 Win. Mag. is perhaps the most flexible of the big bore elephant cartridges, and the obvious choice for North American big game hunters.
Copyright 2001, 2012 by Chuck Hawks. All rights reserved.