.458 Winchester Magnum

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The .458 Winchester Magnum is a rifle cartridge introduced 1956 by Winchester. 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 350 grain (22.7 g).

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 2250 feet per second (690 m/s). They use a special propellant ("powder") not available to the public for reloading. Numerous companies offer rifles in this caliber, including the Winchester Model 70.

The cost of these rounds are prohibitive, leading to a high number of handloaded cartridges. The recoil of the factory loads is about 70 foot pounds. Handloads can be made that will make this cartridge more comfortable to shoot.