.500 Nitro Express
| .500 Nitro Express | ||||||||||||||||
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.500 Nitro Express round
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| Type | Rifle | |||||||||||||||
| Place of origin |
 United Kingdom
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| Production history | ||||||||||||||||
| Designer | Westley Richards | |||||||||||||||
| Designed | 1890 | |||||||||||||||
| Variants | .500 BPE, .500 Nitro for BP | |||||||||||||||
| Specifications | ||||||||||||||||
| Parent case | .500 Black Powder Express | |||||||||||||||
| Bullet diameter | .510 in (13.0 mm) | |||||||||||||||
| Neck diameter | .535 in (13.6 mm) | |||||||||||||||
| Base diameter | .580 in (14.7 mm) | |||||||||||||||
| Rim diameter | .660 in (16.8 mm) | |||||||||||||||
| Rim thickness | .040 in (1.0 mm) | |||||||||||||||
| Case length | 3.01 in (76 mm) | |||||||||||||||
| Overall length | 3.68 in (93 mm) | |||||||||||||||
| Case capacity | 138 gr H2O (8.9 cm3) | |||||||||||||||
| Rifling twist | 1 in 15 | |||||||||||||||
| Primer type | .251 (6.38 mm) Berdan (Kynoch #31A) | |||||||||||||||
| Maximum pressure | 40,600 psi (280 MPa) | |||||||||||||||
| Ballistic performance | ||||||||||||||||
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| Source(s): Barnes & Amber 1972 | ||||||||||||||||
The .500 Nitro Express is a .510 caliber (13 mm) big bore hunting cartridge. It was designed for use in single shot and double rifles. The cartridge is available in two lengths: a 3.00 in (76 mm) and a 3.25 in (83 mm) version. The cartridge was designed for use against large dangerous game species in Africa and India.
The nomenclature .500 Nitro Express refers to one of three specific loading of the .500 Express case. The other loadings are now called (for the sake of clarity) the .500 Black Powder Express (BPE) and .500 Nitro for Black Powder (Nitro for BPE). The names given to these loadings are of more modern origin to help one differentiate between them. The original cartridge was simply known as the .500 Express. The cartridge is one of the original Express cartridges which originated in the black powder era and made the transition into the smokeless powder era.
The .500 Black Powder Express, as the name indicates was designed for use with black powder. It is unknown as to who or which company originally designed the cartridge except that it was designed sometime in the 1860s in the United Kingdom. Several manufacturers of firearms produced rifles and loaded ammunition for the cartridge type, however significant differences and variations existed between manufacturers. For the most part, due to the relatively low working pressures of these rifles and ammunition there was little to no danger associated with the use of these cartridges in a particular rifle.
The .500 Nitro for Black Powder cartridge used the same general case type as the .500 Black Powder Express but was loaded with cordite instead of black powder and appeared on the scene sometime in the 1890s. The cartridge was intended for firearms designed to fire the .500 Black Powder Express and pressures were kept low enough so as to operate safely in these older black-powder firearms yet provided a substantial increase in performance over the black-powder–loaded cartridge.
Cordite, which was invented in 1889, gave cartridges a greater performance envelope than black powder at the expense of pressure. Rifles that were designed for use with cordite cartridges required stronger actions which were able to withstand the significantly higher pressures to take advantage of the increase in performance offered by cordite. As the working pressure of the .500 Nitro Express cartridge was significantly higher than the black-powder cartridge, variations between manufacturers of the same ammunition would result in damage to the firearms and injury to the shooter. For this reason there is an acknowledged standard between manufacturers for the .500 Nitro Express cartridge but not for the earlier black-powder cartridge.
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