The .450 Black Powder Express, also known as the .450 3¼-inch BPE and 11.43×82.9mmR Express, was a black powder hunting rifle cartridge of British origin in the 19th and 20th century.
The .450 Black Powder Express is a rimmed, straight-walled, centerfire rifle cartridge made for use with black powder. It was available in a variety of loadings with projectiles weighing 270 to 365 grains (17.5 to 23.7 g), all driven by 120 grains (7.8 g) of black powder.
The casing came in different compositions, from cardboard over an iron sleeve, to a rolled or "coiled" brass sheet joined to a steel or brass base, to solid brass.
One of the most popular hunting cartridges that was ever made, it was used for shooting deer and game of similar size, as well as large and dangerous game up to and including elephant.
The .450 Nitro for Black is the same cartridge, this time loaded with mild loadings of cordite smokeless propellant carefully balanced through trial and error to replicate the ballistics properties of the original black powder loads.
The .450 Black Powder Express was also used as the parent case for the .450/400 Black Powder Express, which in turn would become the basis for the cordite-charged .450/400 Nitro Express, which further developed into the .400 Jeffery Nitro Express. It also became the basis for the very first Nitro Express cartridge, the .450 Nitro Express.
In Britain during the 19th century, there were a number of straight-walled .450 caliber cartridges developed in varying case lengths up to 3¼ inches.
The .450 3¼-inch Black Powder Express cartridge was originally designed as an experimental military cartridge for the 1869 British Army Rifle trials that lead to the adoption of the Henry-Martini rifle.
The original military trial "long chamber" cartridge was loaded with a 480 grain (31 g) bullet, though for miltiary usage it was found to be awkwardly lengthy and difficult to handle and load. In response, Eley Brothers developed the much shorter, bottlenecked .577/450 Martini-Henry cartridge.
In the 1870s, the .450 3¼-inch "long chamber" cartridge became the basis for the .450 Black Powder Express when loaded with lighter projectiles fired at higher muzzle velocities than the original. The .450 Black Powder Express was the most popular sporting Express cartridge and was produced in the U.K., France, Germany, Austria, and Canada. It was also readily available in both black powder and Nitro for Black versions well into the 20th century.