bullet

thumb|7.5×55mm Swiss full metal jacket, armor piercing, tracer, and spitzer projectiles. The three bullets on the right show [[cannelure evolution.]] thumb|Schlieren imaging|Schlieren image sequence of a bullet traveling in free-flight, demonstrating the air pressure dynamics surrounding the bullet A bullet is a kinetic projectile, a component of firearm ammunition that is shot from a gun barrel. They are made of a variety of materials, such as copper, lead, steel, polymer, rubber and even wax; and are made in various shapes and constructions (depending on the intended applications), including specialized functions such as hunting, target shooting, training, and combat. Bullets are often tapered, making them more aerodynamic. Bullet size is expressed by weight and diameter (referred to as "caliber") in both imperial and metric measurement systems. Bullets do not normally contain explosives but strike or damage the intended target by transferring kinetic energy upon impact and penetration.

==Description== The term bullet is from Early French, originating as the diminutive of the word boulle (boullet), which means "small ball". Bullets are available singly (as in muzzle-loading and cap and ball firearms) but are more often packaged with propellant as a cartridge ("round" of ammunition) consisting of the bullet (i.e., the projectile), the case (which holds everything together), the propellant (which provides the majority of the energy to launch the projectile), and the primer (which ignites the propellant). Cartridges, in turn, may be held in a magazine, a clip, or a belt (for rapid-fire automatic firearms). Although the word bullet is often used in colloquial language to refer to a cartridge round, a bullet is not a cartridge but rather a component of one. This use of the term bullet (when intending to describe a cartridge) often leads to confusion when a cartridge and all its components are specifically being referenced.