.458 Winchester Magnum

The .458 Winchester Magnum is a rifle cartridge introduced 1956 by Winchester Repeating Arms Company. The cartridge case is based on the .375 H&H case shortened to 2.5 in (64 mm), and "blown out" (case opening enlarged) to accept a bullet of .458 inch (11.6 mm) diameter. With good handloads one can expect approximately 2170 feet per second (660 m/s) using 500 grain (32.4 g) bullets (achieved using a barrel 24 inches (610 mm) in length). It can be loaded with bullets as light as 300 grains.

Winchester no longer sells ammunition in .458 Winchester Magnum, but other manufacturers do. Hornady offers what they call a "heavy magnum" loading that features a 500 grain (32.4 g) bullet with a velocity of approx 2260 feet per second (690 m/s). They use a special double-based cooler burning propellant ("powder") not available to the public for handloading. This innovative loading allows the .458 Winchester Magnum to attain 5670 foot pounds of muzzle energy. Federal Cartridge is now loading a 500 grain Barnes X bullet with a sectional density and ballistic coefficient that allows it to maintain approximately 2000 foot pounds of energy at 500 yards and a flatter trajectory that has never been attained with this cartridge and bullet weight. Numerous companies offer rifles in this caliber, including the Winchester Model 70.

The rounds for the .458 Win mag are expensive, making handloading a worthwhile effort. The recoil of the factory loads is about 70 foot pounds. Handloads can be made that will make this cartridge more comfortable to shoot, for example using a 300 grain Cast lead bullet at 1282 ft/sec.

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Cartridge:rifles