In the late 15th century, the Ottoman Empire used firearms as part of its regular infantry.The earliest surviving firearm in Europe was found in Otepää, Estonia and it dates to at least as early as 1396.Early cartridge firearms had to be cocked and caught by the "sear", which holds the hammer back, before each shot.Pulling the trigger allows the hammer or striker to fly forward, striking the "firing pin," which then strikes the "primer," igniting an impact-sensitive chemical compound (historically, first fulminate of mercury, then potassium chlorate, now lead styphnate) which shoots a flame through the "flash hole" into the cartridge's propellant chamber, igniting the propellant.
A repeating firearm or "repeater" is a firearm that holds more than one cartridge and can be fired more than once between chargings.
Firing a double-action revolver in single-action mode tends to be more accurate, because the trigger pull is much shorter and lighter; usually three or four pounds-force (18−22 newtons) of pull is sufficient, instead of the twelve to twenty pounds (50−90 N) required for double-action mode, so the firearm's aim and mobility is less likely to be disturbed by the force of pulling the trigger.
The first successful rapid-fire firearm is the Gatling gun, invented by Richard Jordan Gatling and fielded by the Union forces during the American Civil War in the 1860s.
The double-action revolver is a design almost as old as the single action. revolvers can only be fired using the trigger (e.g., revolvers with bobbed or hidden hammers).
Some double-action revolvers, called double-action only or D. Most double-action revolvers can be fired in either of the two ways.