bullet

A bullet is a kinetic projectile and a component of firearm ammunition that is expelled from a gun barrel during shooting. The term is from Middle French and originated as the diminutive of the word boulle (boullet), which means "small ball". Bullets are made of a variety of materials such as copper, lead, steel, polymer, rubber and even wax. They are available either singly, as in muzzle-loading and cap and ball firearms, or as components of paper cartridges, but much more commonly in the form of metallic cartridges. Bullets are made in various shapes and constructions depending on the intended applications, including specialized functions such as hunting, target shooting, training and combat.

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. A round of ammunition cartridge is a combination package of the bullet (which is 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). This use of the term bullet when intending to describe a cartridge often leads to confusion when the components of a cartridge are specifically referred to.

 1. bullet; 2. case; 3. propellant; 4. rim; 5. primer

Bullet sizes are expressed by their weights and diameters (referred to as "calibers") in both imperial and metric measurement systems. For example: 55 grain .223 caliber bullets are of the same weight and caliber as 3.56 gram 5.56mm caliber bullets. A grain is an obsolescent unit of measurement of mass, and in the troy weight, avoirdupois, and Apothecaries' system, equal to exactly 64.79891 milligrams. Troy [特洛伊] weight a system of weights used mainly for precious metals and gems, with a pound of 12 ounces or 5,760 grains. Avoirdupois is a system of weights based on a pound of 16 ounces or 7,000 grains, widely used in English-speaking countries. Apothecaries: 药剂师。磅分常衡和金衡，吨分英国长吨、美国短吨、公制吨

The bullets used in many cartridges are fired at muzzle velocities faster than the speed of sound — about 343 metres per second (1,130 ft/s) in dry air at 20 °C (68 °F) — and thus can travel a substantial distance to a target before a nearby observer hears the sound of the shot.

Expanding bullets, also known colloquially as dumdum bullets, are projectiles designed to expand on impact. This causes the bullet to increase in diameter, to combat over-penetration and produce a larger wound. This leads to a living target being incapacitated faster. For this reason they are used for hunting and by most police departments, but are generally prohibited for use in war. Two typical designs are the hollow-point bullet and the soft-point bullet.

Expanded .458 hunting round, after killing an African buffalo; Drawings from 1870 of a hollow point express rifle bullet before firing (1, 2) and after recovery from the game animal (3, 4, 5), showing expansion and fragmentation:

 

  

Dodging a Bullet: The Indian Rebellion | HistoryNet

六级/考研单词: bullet, component, ammunition, expel, copper, rubber, wax, construct, hunt, combat, seldom, parcel, propel, ignite, confuse, diameter, imperial, grain, velocity, thereby, nearby, shot, wound, prohibit