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.
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's line for the .458 Win. Mag. 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.
Reloaders have their choice of 300, 350, 400, 450, and 500 grain bullets in hollow point, soft point, premium controlled expansion, and solid (full metal jacket) types. They also have the option of reduced power and recoil loads for CXP2 and CXP3 class game that can considerably increase the versatility of the .458 Win. Mag. cartridge. It is a good idea to crimp bullets in high power reloads, as the ferocious recoil of the .458 can cause bullets to set back in the case if they are not crimped in place.
Medium burning rifle powders generally work best for full power loads in the .458's straight wall case. These include such numbers as H335, H4895, IMR 3031, and IMR 4895.
In my experience, SR 4759 powder has proven more accurate and more reliable than IMR 4198 or H4198 in light .458 Mag. loads. And the Speer 400 grain FP bullet has proven a better choice than the 300 grain HP bullets intended for .45-70 loads.
Here are some specifications of interest to .458 Mag. reloaders: bullet diameter .458", maximum COL 3.34", maximum case length 2.50", MAP 53,000 cup.
Here are useful .458 Mag. loads for hunting CXP2 class game in the woods, courtesy of the Speer Reloading Manual, Number 13. 26.0 grains of SR 4759 powder behind a 400 grain Speer flat point bullet will give a MV of 1262 fps, and 30.0 grains of SR 4759 behind the same bullet gives a MV of 1445 fps. These loads were tested in a 24" rifle barrel using Winchester cases and CCI 250 primers.
I load 29.0 grains of SR 4757 for a MV of about 1400 fps with the Speer 400 grain bullet, essentially duplicating the traditional .45-70 factory load. This load is exceptionally accurate in my Browning/FN rifle.
For hunting CXP3 class game, I use the Hornady 350 grain RN bullet and IMR 3031 powder. The sixth edition of the Hornady Handbook of Cartridge Reloading shows that 64.3 grains of IMR 3031 powder behind a 350 grain bullet gives a MV of 2100 fps. That is the load I use. A maximum load of 75.5 grains of IMR 3031 can drive a 350 grain Hornady bullet to a MV of 2400 fps.
For CXP4 class game, 67.5 grains of H335 powder behind a 500 grain Hornady bullet gave a MV of 1950 fps, and a maximum load of 76.3 grains of H335 gave a MV of 2150 fps. All of these loads from the Hornady Handbook used Winchester cases and Win. WLRM primers, and were chronographed in a 24" rifle barrel.
Note: A full length article about the .458 Winchester Magnum can be found on the Rifle Cartridge Page.
Copyright 2004, 2012 by Chuck Hawks. All rights reserved.