A semi-automatic firearm requires a trigger pull for each round that is fired. For example, if someone were to shoot ten rounds in a semi-automatic firearm, they would need to pull the trigger ten times (once for each round fired). Compare this to a fully automatic firearm, which will continue to fire as long as the trigger is held or until it runs out of ammunition. Pistols, rifles, and shotguns can all be semi-automatic. A semi-automatic option is a common choice on selective fire firearms. Some firearms A firearm is a kinetic energy mechanical device that fires either a single or multiple projectiles propelled at high velocity by the gases produced by action of the rapid confined burning of a propellant. ... M2 heavy machine gun An automatic firearm is a firearm that will continue to load and fire ammunition as long as the trigger (or other activating device) is pressed or until it runs out of ammunition. ... Boxes of ammunition clog a warehouse in Baghdad Ammunition is a generic military term meaning (the assembly of) a projectile and its propellant. ... For the coin, see pistole For the part of a flower, see pistil. ... A rifle is any long gun which has a rifled barrel. ... Shotguns and boxes of ammunition A shotgun is a firearm typically used to fire a number of small spherical pellets, the shot, from a smoothbore barrel of relatively large diameter. ... A selective fire weapon can be fired in either of at least two modes, depending on the position of the selector switch. ...

Semi-automatic weapons are sometimes divided into two categories: those that fire from an open bolt and those that fire from a closed bolt. When the trigger is pulled, the open bolt flies forward, picking up a cartridge from the magazine and ramming it into the chamber and the gun fires. The closed bolt system moves the bolt forward and picks up the cartridge as the last phases of the previous cycle, and when the trigger is pulled again only the firing pin moves. The closed bolt system is generally more accurate, since the center of gravity changes relatively little. The open bolt system is almost exclusively used in submachine guns, as it also lets the barrel cool more quickly. A semi or fully-automatic firearm which is said to fire from an open bolt is one where, when ready to fire, the bolt and working parts are held to the rear. ... A semi or fully_automatic firearm which is said to fire from a closed bolt is one where, when ready to fire, a round is in the chamber and the bolt and working parts are forward. ... The firing pin is a very hard steel rod with a one small, rounded end for striking the primer of a cartridge. ... In physics, the center of gravity (CoG) of an object is the average location of its weight. ... MP5KA4 9 x 19 mm with 3-round burst trigger group A submachine gun is a firearm that combines the automatic fire of a machine gun with the ammunition of a pistol, and is usually between the two in weight and size. ...

There is some casual dispute over the correct use of the words automatic and semi-automatic. Gun enthusiasts sometimes argue that the word automatic is often linked to fully automatic fire and that an automatic weapon is simply any weapon that chambers a new round during the extraction of the previous cartridge's casing. The term is often used to mean a self-loading semi-automatic firearm rather than a fully automatic one. One narrow definition would be that a semi-automatic firearm would thus be a weapon using the open bolt system, and the semi-automatic function is simply the removal of the case, whereas an automatic weapon would both remove the empty case and chamber a fresh cartridge. In practice, a automatic pistol usually means a self-loading semi-automatic pistol but a automatic rifle usually means one capable of fully automatic fire (as opposed to a semi-auto SLR). Both uses can be found, and the exact meaning must be determined from context. M2 machine gun An automatic firearm is a firearm that will continue to load and fire rounds of ammunition as long as the trigger (or equivalent) is activated or until it runs out of ammunition. ...

See also

• Self-loading pistol
• Semi-automatic rifle