The lock of a firearm is the mechanism used to initiate firing. From the earliest guns, the propellent charge was lit through a touch hole. In firearms, a flash pan next to the touch hole was filled with a small priming charge. Mechanisms would light the priming charge by touching it with a lit piece of slow match or by creating sparks. Percussion caps replaced loose gun powder as the priming charge. They were fitted over a nipple screwed into the end of the touch hole and ignited by striking with a hammer. With the advent of metallic cartrides, the priming charge was incorporated into the cartridge and would be inside the chamber of the firearm. The percussion cap had to be struck by a firing-pin that passed through the breechblock. The firing-pin would be struck by a hammer or the firing-pin may be an extension of the hammer.
Many modern firearms use a spring-loaded striker rather than a hammer and firing-pin to set-off the primer of a metallic cartridge. The striker is aligned with the axis of the barrel. It is more usual to refer to the components of this type of system as the trigger mechanism, while the term lock is more commonly used to refer to mechanisms used in muzzeloading firearms. An exception is break action longarms and particularly, shotguns.
The earliest firearms were cannon mounted on carriages and ignited by a glowing ember or slow match. As the mobility advantages of smaller hand-held cannon were explored, the difficulty became obvious for a single individual to simultaneously move the slow match from a safe storage location to the ignition vent while keeping the cannon pointed at the target. The matchlock was devised to quickly move the slow match to the ignition vent when the trigger was actuated while holding the slow match safely away from the ignition vent at other times. The earliest locks may have been a simple lever centrally pinned to the firearm with the slow match at one end while the opposite end was held for movement. A major improvement was spring loading that lever toward the ignition vent with a catch to hold the lever away from the vent until the catch was released by a trigger. The essential elements of a trigger and moving parts near the rear of the barrel evolved through the wheellock, snaplock, snaphance, doglock, miquelet lock, flintlock, and caplock. The term firelock was originally applied, as the name suggests, to the matchlock, but was later successively applied to the wheellock and then the flintlock as each was invented.
As muzzleloaders were replaced by metallic cartridge firearms the lock functions have been included as part of the receiver and ammunition handling mechanism known as the firearm action. A few modern firearms include electronic firing mechanisms.
Lock, stock and barrel is a figure of speech referring to the totality of a firearm as: the barrel through which the bullet is directed toward a target, the stock which provides a means of gripping the firearm, and the lock as the firing mechanism.
- Bolt (firearms)
- Flintlock mechanism
- Bolt action
- Falling-block action
- Rolling block
- Semi-automatic rifle
- Ramage, C. Kenneth (1980). Cast Bullet Handbook (3rd ed.). Middlefield, Connecticut: Lyman Publications. p. 8.
- Pennsylvania Archaeologist. 36–40. Society for Pennsylvania Archaeology. 1966. p. 13.
- Penny cyclopaedia of the Society for the Diffusion of Useful Knowledge, Penny cyclopaedia of the Society for the Diffusion of Useful Knowledge, Vol.1, p. 375, C. Knight, 1833.
- Craige, John Houston (1950). The Practical Book of American Guns. New York: Bramhall House. pp. 102&103.