The .500 Jeffery (12.7x70mmRB) is a big-game rifle cartridge that first appeared around 1920, and was originally introduced by the August Schuler Company, a German firm, under the European designation "12.7×70mm Schuler" or ".500 Schuler". When offered by the famed British outfitter W.J. Jeffery & Co, it was renamed the .500 Jeffery so as to be more palatable to British hunters and sportsmen following World War One.^[1]

The .500 Jeffery was introduced to bring firepower comparable to the .505 Gibbs into a standard-sized 1898 Mauser action as used with the 8x57mm and 7x57mm cartridges. The Gibbs and .416 Rigby cartridges required oversized magnum Mauser actions. To shoehorn a large round into the 98 action required a rebated rim. When introduced, the .500 Jeffery was technically rated as the most powerful rifle cartridge although in reality not quite up to .505 Gibbs' performance. The .505 Gibbs, with greater capacity, can be loaded far in excess of the .500 Jeffery today.

Like the .505 Gibbs, the .500 Jeffery is enjoying somewhat of a renaissance among American shooters and African big game hunters in the early 21st century, almost 100 years after its introduction.^[2] As of 2009, Norma, Kynoch, Mauser, Corbon, and Westley Richards were offering loaded ammunition in .500 Jeffery with ammunition costing $150 for a box of 20 or more.

There have been a few rifles chambered in the .500 Jeffery including Jeffery, Heym, CZ-USA, and a few single shots including the Ruger No. 1, and the Butch Searcy & Co. Mauser offers its Model 98 magnum in the caliber. Its "elephant" model is offered in .500 Jeffery exclusively. In 2011, Sako began offering the caliber in its Model 85 "safari" rifle using a new XL size action, and since 2014 the XL action has been available in the more affordable Model 85 brown bear rifle. Blaser also offers rifles chambered in the caliber. Many of the modern rifles have feeding issues due to the rebated rim. The original Jeffery uses a single-column two-shot magazine to get around the potential reliability problems resulting from a rebated rim.

The .500 Jeffery has had a few issues since its introduction. It has a rather short neck length that can make it difficult to seat bullets with a relatively high sectional density. Also it has a small shoulder. This is not usually an issue but as the .500 Jeffery also has a rebated rim it makes it rather difficult to extract in extreme conditions.

When the .500 Jeffery was first introduced it was loaded to a velocity of 2,350 feet per second (720 m/s) topped off with a 535-grain bullet generating 6,560 ft⋅lbf (8,890 J) of muzzle energy, which made it a pretty good hunting caliber for thick-skinned dangerous game. Since then, reloading capabilities have advanced to be able to launch heavier bullets at higher velocities. Now, with modern reloads, the .500 Jeffery can launch a 600-grain bullet at a muzzle velocity ranging from 2,450 to 2,500 ft/s (750 to 760 m/s), generating 7,995 ft⋅lbf (10,840 J) to 8,100 ft⋅lbf (11,000 J) Newer reloads made the .500 Jeffery the most powerful production cartridge in the world until the introduction of the .460 Weatherby Magnum. With reloads the .460 Weatherby can reach levels of power of about 8,300 ft⋅lbf (11,300 J) of muzzle energy. Also the .600 Nitro Express exceeds the .500 Jeffery in muzzle energy, with 120 grains of cordite.

• .50 BMG
• .500 A-Square
• .500 Nitro Express
• .577 Nitro Express
• .577 Tyrannosaur
• .600 Nitro Express
• .700 Nitro Express
• List of rebated rim cartridges

• African Conservation Foundation on .505 Gibbs and .500 Jeffrey Archived 2006-09-02 at the Wayback Machine
• AccurateReloading.Com on the .500 Jeffery
• Norma Ammunition .500 Jeffery page
• RealGuns.com page on .500 Jeffery reloading data
• RealGuns: The 500 Jeffery Project (Part I)
• RealGuns: The 500 Jeffery Project (Part II)
• Kynoch Ammunition