The first American revolver makers caused the cocking of the hammer to revolve the cylinder, while the English makers effected this by the pull of the trigger. In 1855, Adams of London, and also Tranter of Birmingham, brought out the double-action re volver, in which the revolution of the cylinder could be effected by both these methods. When the revolver is cocked and fired by pressing the trigger, greater rapidity of fire is obtained than when the hammer is cocked with the thumb, but accuracy is im paired, as the trigger requires a long pull and considerable force in order to compress the mainspring and revolve the cylinder. The double action revolver was, therefore, a great advance on the single action, enabling the first and also following shots, if desired, to be accurately fired by a moderate pressure of the trigger of ter the hammer had been cocked by the thumb ; or, alternatively, the revolver could be rapidly fired, if necessary, by the trigger action alone. Many revolvers on the Colt principle were in use during the Crimean War and the Indian Mutiny, and proved of valuable service to British officers.
As rim-fire, pin-fire and central-fire cartridges were succes sively introduced, breech-loading revolvers were constructed to use them. Messrs. Smith & Wesson, of Springfield, U.S.A., pro duced the first metal cartridges for revolvers. Pin-fire cart ridges, paper and metallic, were used on the continent of Europe for Lefaucheux and other revolvers, and these and rim-fire cart ridges are still used for revolvers of small calibre. But since the central-fire cartridge has proved its superiority for guns, its principle has been generally applied to pistol cartridges.
The alteration of the muzzle-loading to the breech-loading chamber in the revolver involved no decided change of type. The original Colt, as a breech-loader, remained practically the same weapon as before, with a changed chamber. A hinged flap uncovered the breech-chamber on the right, and as each chamber reached that point the empty cartridge case was ejected by means of an ejecting-rod carried in a tube attached to the under side of the barrel and kept in place by a spiral spring, and the chamber reloaded. The next improvement was greater ease and rapidity of extraction, obtained first by Thomas's invention of making the barrel and chamber slide forward on the frame of the pistol. The extractor, being fast to the pivot, re tained the cartridges until the chamber was pushed clear of them.
Then the chamber was made to swing on one side, as in the Colt pistol of that time, enabling all the cartridges to be simultaneously extracted. Finally, self-extracting revolvers with jointed frames were introduced, in which the dropping of the barrel forces out the extractor as in an ordinary double gun, the extractor acting simultaneously in all the chambers of the pistol. A spring returns the extractor to its place when the empty cartridge cases have been ejected. These are now known as "break-down" actions.
This type of revolver originated with Smith and Wesson, but they and other gun makers greatly improved on the original model. Between this American pattern and the English, as made by Webley, the chief difference is that in the Smith and Wesson, model 1888, the holding-down bolt or catch was upon the barrel, and it engaged with the top of the standing breech ; whereas in the Webley the bolt was upon the standing breech and gripped the extremity of the hinged barrel. In the .45, 1902 model, used by the British in the World War, this catch was eliminated. The frame was solid and the cylinder made to swing out to the left for the purpose of extracting, ejecting and recharging. The hinged type of revolver is most convenient for use on horseback, as the pistol can be opened, the cartridges extracted and the weapon reloaded with one hand.