The .458 African
By Chuck Hawks
Pierre van der Walt recently sent me a copy of his new book African Dangerous Game Cartridges for review. In it he covers in detail almost every African DG safari cartridge anyone is liable to use to hunt the Big Five, from the 9.3x62mm Mauser to the .600 Nitro Express. Among them is the .458 African, a wildcat designed and developed by Pierre himself over about a 10 year period between 1995 and 2005. He designed this cartridge to meet several specific goals relevant to African hunting by Africans. These are:
As you can see, the .458 African is a practical cartridge designed for a real world purpose. As Pierre relates in African Dangerous Game Cartridges, he chose the .404 Jeffery as the parent case. (The .375 RUM case can be substituted, as it is a slightly rebated rim version of the .404 Jeffery.) He explains how he basically started with the .460 G&A and then addressed the various aspects of good cartridge design, including case capacity, magazine capacity, headspacing, shape and feeding, neck length and tension, pressure levels (especially considering use in the hot African sun), powder availability in his homeland of South Africa, powder burn-out versus barrel length, bolt throw and other factors.
The shoulder angle was set at 35-degrees to eliminate any question about positive headspacing, without sacrificing reliable feeding. Body taper was reduced to increase powder capacity. Neck length is one caliber, generally considered to be optimum. After considerable experimentation, the case length was set at 2.6730" (trim to 2.665"). Case capacity is 115.5 grains of water. Bore diameter is .450" and bullet diameter is .458". Standard barrel twist is 1:10". MAP is 62,365 psi piezo CIP.
Somchem volunteered to do .458 African pressure tests with several of their powders using bullets ranging in weight from 350 grains to 500 grains, which is very unusual for any wildcat cartridge. Suitable powders include Somchem S-321, S-335, S-341 and S-355. For example, with a 500 grain bullet the minimum load of Somchem S-355 is 83.0 grains and the maximum load is 90.0 grains. The latter delivers a MV of 2316 fps and ME of 5955 ft. lbs. from a 24" pressure test barrel at 56,959 psi.
See African Dangerous Game Cartridges for additional details, including 28 recommended loads for various bullet weights up to 550 grains. For North American users, medium burning rate powders on the order of RL-15, Norma N-203, IMR 4320, IMR 4064, Varget, BL-C2, H4895 and H335 are suitable choices.
Ultimately, the performance of the .458 African exceeded the design goal of at least 2150 fps with a 500 grain bullet from a 22" barrel. Pierre reports that muzzle velocities (MV) from 22" barrels run about 2225 fps at a MAP of 60,000 psi using South African Somchem powders. The muzzle energy (ME) of that load is 5496 ft. lbs. At 100 yards the figures are 1962 fps and 4274 ft. lbs.
Pierre suggests a 75 yard zero for a scoped dangerous game rifle (1.5" sight height). With 450-500 grain bullets that should keep the bullet's trajectory within ½" of the line of sight out to 100 yards.
For comparison, if you zero a 500 grain Hornady RN-FMJ solid bullet (BC .295) at a MV of 2225 fps to hit 3" high at 100 yards to take advantage of the cartridges maximum point blank range (+/- 3"), the trajectory would look like this: -1.5" at muzzle, + 0.4" at 25 yards, +1.7" at 50 yards, +2.6" at 75 yards, +3" at 100 yards, +2.8" at 125 yards, +2" at 150 yards, +0.5" at 175 yards, +/- 0" at 182 yards, -1.6" at 200 yards and -3" at 214 yards. The MPBR is thus 214 yards.
The .458 African is a very tightly focused wildcat, so much so that it is unlikely to be adopted by a major ammunition manufacturer, although Horneber is now offering new, correctly headstamped brass. It is a cartridge designed for African shooters/reloaders hunting African dangerous game. It is overly powerful for any likely North American, South American, Asian, European or Australian application, but just what the doctor ordered if you have elephants in your pea patch or an aggressive hippo in your pond. The .458 African is a virtually perfect example of a modern, purpose built, wildcat cartridge.
Copyright 2012 by Chuck Hawks. All rights reserved.