March 22, 2022
By Layne Simpson
The .458 Winchester Magnum is a fairly modern cartridge, but its story begins back in 1898. That’s when John Rigby, an Englishman famous for building high-quality double-barrel rifles, loaded the case of the old .450 Black Powder Express with 70.0 grains of a then-new high-nitroglycerine-content smokeless propellant called cordite and renamed it the .450 Nitro Express 3¼ inches. Advertised velocity for three styles of 0.458-inch bullets weighing 480 grains was 2,175 fps, but since they were from 28-inch pressure barrels and mixed with a pinch of exaggeration, actual velocity from the 26-inch barrels of double rifles usually ranged from 2,025 to 2,075 fps. Cordite had a tendency to become less potent as it aged, with velocity sometimes falling short of 2,000 fps. Even so, that level of performance obviously proved to be quite sufficient for taking on the biggest game Africa had to offer.
To quote professional ivory hunter John Taylor from his classic book "African Rifles & Cartridges" (1948), “The .450 Nitro Express 3¼" became the most popular and widely used caliber for all heavy and dangerous game throughout the world. It took the big game hunting world by storm and immediately became a standard caliber in the British gun trade. The full-patch (solid) bullet is excellent for elephant; the soft nose is quite effective when taking side-on shots at buffalo and frontal chest shots on lion. For a broadside shot on lion, the split-jacket soft nose is preferred.”
During about the first three decades of the 20th century, the cost of an African safari was beyond the reach of most Americans. That eventually began to change, and among American manufacturers, Winchester was first to respond to the demand by offering the .375 Holland & Holland Magnum in the Model 70 in 1937. In the hands of a cool-headed hunter and good shot, the rifle was capable of handling all African game, but when the chips were down, larger calibers had proven to be more reliable stoppers of elephant, buffalo, and rhino.
During the 1940s, Alaskan school teacher James Watts began planning a lengthy safari in Rhodesia and decided to duplicate the performance of the .450 Nitro Express 3¼" by necking up the .375 H&H Magnum for 0.458-inch 480-grain bullets made by Kynoch and fireforming the case to straight taper with no shoulder. He called it the .450 Watts, and obtaining a rifle was as easy as switching barrels on a Winchester Model 70 in .375 H&H Magnum. Except for being 0.050 inch longer, the .450 Watts case is identical to the .458 Lott introduced about 30 years later.
Jack O’Connor wrote about using a custom rifle in .450 Watts on buffalo and other dangerous game, and the cartridge took off like a rocket. Fully formed cases with the proper headstamp were offered by Dick Speer of Lewiston, Idaho, who founded Cascade Cartridge Co. and was a brother to Vernon Speer, founder of Speer Bullet Co. Today, .450 Watts cases are made by Quality Cartridge of Hollywood, Maryland. I have rifles in the Watts and Lott chamberings and use Hornady .458 Lott cases in both. Reloading dies and load data are interchangeable.
During the early 1950s, Winchester began planning a new family of belted magnum cartridges for the Model 70, with .45 caliber first on the list. The .450 Watts was seriously considered, but at the time, military-surplus 1898 Mauser rifles were abundant and cheap, and gunsmiths across the country were busy building custom rifles around them. So the entire family of Winchester cartridges was made short enough for the Mauser action. The .450 Watts case was shortened from 2.850 inches to 2.500 inches and introduced in 1956 as the .458 Winchester Magnum.
The original goal was to match the performance of the .450 Nitro Express, but in the spirit of one-upmanship, bullet weight was increased to 510 grains for the softnose and 500 grains for the solid, both at 2,125 fps. Claimed muzzle energies of the two loads were 5,140 and 5,010 ft-lbs compared to 4,110 ft-lbs for the .450 Nitro Express. Advertised velocities of the two bullet weights were later reduced to 2,040 fps.
Not long after the .458 Win. Mag. was introduced, complaints of drastically reduced velocities caused by excessive compression of the powder charge in factory ammunition began to trickle in from professional hunters in Africa. Winchester eventually corrected the problem, but it would haunt the cartridge for many years.
Despite that very large bump in the road, the “four-five-eight” became a favorite among sport hunters headed to Africa and among professional hunters there who used it for backing up their clientele. Various African game departments adopted the Model 70 and other rifles chambered for the cartridge for animal population control. Many thousands of elephant and buffalo were taken over the years. During my first hunt for buffalo in Rhodesia during the 1970s, I saw several tons of biltong drying on racks in the sun, all of it harvested by government-employed cullers using rifles in .458 Win. Mag.
There are several reasons why the .458 Win. Mag. eventually became hugely popular around the world and remains so today. For starters, when Kynoch ceased production of all calibers of rifle ammunition in 1970, an abundant supply of .458 ammo was available from Winchester and Remington at far less cost. Once Winchester sorted out the velocity variation problem, the performance of the cartridge on large, dangerous game left nothing to be desired, at a level of recoil easily tolerated by experienced hunters. Last but certainly not least in importance, the Winchester Model 70 African was durable, reliable, and accurate enough, and for the money, it was the world’s greatest big-game rifle. It had a 25-inch barrel and weighed 9.25 pounds. There is some recoil, and the Model 70 Super Express I have today, weighing 10 pounds with a 1.5-5X scope, leather sling, and three rounds in its magazine, is none too heavy. A custom rifle on a Weatherby Mark V action
I used to take a dozen buffalo weighed 10.75 pounds, and carrying it on 25-mile treks under an African sun was never a task.
Hornady, Swift Bullets, Federal Premium, Barnes Bullets, Norma Shooting, and Winchester continue to catalog ammo, and it is not unusual for some to exceed the long-standing 2,040 fps rating from a 24-inch barrel. Handloading the .458 increases its versatility by making an elephant rifle suitable for use on deer. Hornady and Winchester offer unprimed cases, and since the mouths of cases have to be belled slightly prior to bulletseating, die sets contain a third die. To ensure a uniform roll crimp, virgin cases are trimmed to the exact same length. Cases can lengthen slightly with each firing, so keeping them trimmed to 2.490 inches is important.
Due to the limited capacity of the .458 Win. Mag. case, only a few powders of fairly high density have the correct burn rate for producing the desired velocity with 500-grain bullets. As illustrated in various reloading manuals, many powders of lower density can be used, but charge compression is often excessive. Some compression is needed. It is important to keep in mind that a heavy roll crimp alone may not prevent bullets in cartridges in the magazine from being pushed more deeply into the case due to recoil. In addition to increasing chamber pressure, this can cause feeding issues, something that cannot be tolerated with ammunition to be used for taking dangerous game. Choosing a powder with a density that allows a maximum charge to be compressed just enough to prevent bullet shove-back while delivering adequate velocity is important.
When the Hornady and Swift 500-grain bullets are seated with the front edge of their cannelure aligned with the mouth of a case measuring 2.490 inches long, their bases rest 0.625 inch from the mouth of the case. In other words, 25 percent of the powder cavity is occupied. After shortening a case by 0.625 inch, I used a seven-inch drop tube to determine the charge weights of various powders of the correct burn rates that would fill the case to the bases of those bullets.
Beginning with H335, 71.5 grains filled the shortened case to the brim, and increasing it to a maximum of 74.5 grains for a 500-grain bullet resulted in just enough compression in a full-length case to prevent bullet movement during recoil. Moving to Accurate 2230, 68.0 grains filled the case to the base of the bullet with a maximum of 72.0 grains, resulting in about the same amount of charge compression as with H335. Only slightly less dense, 66.0 grains of Accurate 2460 was a 100 percent density load with a maximum charge of 74.0 grains compressed only slightly more than H335 and Accurate 2230. Everything considered, those are the best commonly available powders for use in .458 Win. Mag. handloads. Accuracy is quite good, and when loaded behind a 500-grain bullet, they are capable of exceeding a velocity of 2,100 fps as promised by Winchester back in 1956. Regardless of which is chosen, the Federal 215 and CCI 250 Magnum primers ensure uniform ignition.
Handloading properly constructed 450-grain bullets in the .458 Win. Mag. has become popular among many hunters because they take up less space in the short case and recoil is noticeably less. A sectional density of .300 or greater has long been the benchmark for bullets to be used on large game, and due to the .307 rating of a 450-grain bullet along with its slightly higher velocity, penetration on the largest game has proven to be equal to that of a 500-grain bullet of the same construction. From my rifles, the Swift 450-grain A-Frame and the Cutting Edge Bullets 450-grain Safari Solid shoot to the same point of impact at 100 yards.
Moving down another step in bullet weight, the Swift 400-grain A-Frame is constructed to perform at .458 Win. Mag. velocities. One of my brown bear guides carried a .458 for backup, and its magazine was filled with the 400-grain Swift handloaded to 2,375 fps. He called it the deadliest little bear-stopper in Alaska. For those who do not load their own, Federal ammo is loaded with the 400-grain Trophy Bonded Bear Claw.
Winchester hit a home run with the .458 Magnum back in 1956, and for close-distance stopping of elephant, buffalo, Alaskan brown bear, and other big animals capable of hurting you, it remains one of the best friends you can have on your team.