The Beaumont-Adams Revolver was a muzzle-loading percussion revolver. Originally adopted by the British Army in .442 calibre

.442 Webley

The .442 Webley is a British centrefire revolver cartridge....

 (54-bore, 11.2mm) in 1856, many were later converted to use centrefire

Centerfire ammunition

A centerfire cartridge is a cartridge with a primer located in the center of the cartridge case head. Unlike rimfire cartridges, the primer is a separate and replaceable component....

 cartridges

Cartridge (firearms)

A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...

. It was replaced in British service in 1880 by the .476 calibre

.476 Enfield

The .476 Enfield is a British centrefire black powder revolver cartridge....

 (actually 11.6mm) Enfield Mk I revolver

Enfield revolver

Enfield Revolver is the name applied to two totally separate models of self-extracting British handgun designed and manufactured at the government-owned Royal Small Arms Factory in Enfield; initially the .476 calibre Revolver Enfield Mk I/Mk II revolvers , and later the .38/200 calibre Enfield No...

.
On 20 February 1856, Lieutenant Frederick E.B. Beaumont

Frederick Edward Blackett Beaumont

Frederick Edward Blackett Beaumont was a British officer of the Royal Engineers who produced several inventions, including a tunneling machine which bore his name, and the Beaumont-Adams revolver.-Early life:...

 of the Royal Engineers

Royal Engineers

The Corps of Royal Engineers, usually just called the Royal Engineers , and commonly known as the Sappers, is one of the corps of the British Army....

 was granted a British patent for improvements to the Adams revolver which allowed them to be cocked and fired either cocking the hammer as in Colt single-action revolvers, or by just pulling the trigger.