User:Geek.not.nerd
Bullets are small metal objects fired from guns. They are usually made from lead covered with copper, and are pushed out of the gun by hot gases at a high pressure. A powder called gunpowder is put inside the shell. A small explosion from the primer lights the gunpowder. The gunpowder burn very fast. It makes hot gases. The hot gases are at a high pressure. The high pressure pushes the bullet out of the gun barrel at a high speed. The bullet is put in front of the cartridge, so that when the gunpowder burns, the bullet is forced out at high speed. Bullets have many uses but are mostly used as a weapon in war, for hunting animals for food or as a sport, and for shooting targets.
Design
1. the bullet itself, which is the projectile;
2. the case, which holds all parts together;
3. the propellant, for example gunpowder or cordite;
4. the rim, part of the casing used for loading;
5. the percussion cap or primer, which ignites the propellant.
Bullet designs have to solve two main problems. They must form a seal with the gun's bore (inner surface of barrel). If a strong seal is not there, gas from the propellant charge leaks past the bullet, and do not help push it out. The bullet must also engage the rifling (spiral marks on barrel) without damaging the gun's bore. Bullets must have a surface which will form this seal without causing too muchfriction. The way the bullet behaves in the barrel is called 'internal ballistics'. Bullets must be made to a high standard, or they will not be accurate.
The physics affecting the bullet after it leaves the barrel, is called 'external ballistics'. The main factors affecting the aerodynamics of a bullet in flight are the bullet's shape and the rotation from the rifling of the gun barrel. Spinning helps stabilize the bullet gyroscopically and aerodynamically (spinning keeps it on track). Any asymmetry in the bullet is largely canceled as it spins. With smooth-bore firearms, a round bullet was best because it was the same in any position. These unstable bullets were less accurate; but the round shape of bullets changed little for centuries.
Bullet design affects what happens when a bullet hits an object. The make-up and density of the target material, the angle at which the bullet hits, and the speed and design of the bullet itself are all factors. Bullets are usually designed to penetrate, deform, and/or break apart. For a given material and bullet, the speed of the bullet is the main factor determining what happens.
A basic equation of Kinetic energy goes: : (Kinetic energy = ½mass x velocity2)
Because increasing the speed increases the kinetic energy so much, people have tried (and succeeded) to increase bullet speed and reduce bullet weight. Modern firearms take much lighter bullets, and shoot them much faster than was the case in WWI. This makes the firearms bettering two ways. The magazine holds more of the smaller, lighter bullets, and the higher speed causes much more damage than the old-style bullets.
Bullet types
Bullets are used for target shooting and killing. To do this, a rifle bullet can be described by its accuracy, penetration, shape, size, and mass. There are many different kinds of rifle bullets.
The Full Metal Jacket (FMJ) is a type of bullet commonly used by the military. A lead center (core) is surrounded by a strong metal coating (jacket). The FMJ does not spread out when it hits a target. It goes deep into its target and is a general-purpose bullet. The FMJ is not recommended for hunting. It is mostly for target shooting. The Jacketed Hollow Point (JHP) has a lead center (core) with lead showing at the tip. It also has a strong metal coating (jacket). The center of the tip has a hole in it (hollow point). This design makes the tip of the JHP quickly start to spread out (expand) when it hits a target. The front may spread out to two times as wide as the bullet was when it started. It is a good hunting bullet because the energy in the bullet is transferred to the target at a known depth. The jacketed hollow point tends to be accurate and is sturdy. The plastic tipped bullet is a hollow point bullet. The hollow point is filled with a hard, pointed plastic tip. It is used because it can go further than the JHP and does not curve as much. The plastic tipped bullet also spreads out or breaks into pieces when it hits the target.
A solid copper bullet is a bullet that has no lead core or other elements than copper. This bullet expands into a flower shape on impact, as copper bullets are generally hollow point. As the copper bullet contains no lead, it is also better for the environment.
A frangible bullet will break into many pieces upon contact with any material harder than itself. This bullet is used for safety while shooting. It has little impact on the environment. It also makes the objects behind the intended target a little safer.
A flat nosed bullet is mostly used in handguns, although it can also be used in a rifle. The flat nosed bullet tends to have a low ballistic coefficient. This means that it slows down faster than pointed bullets Flat nosed bullets are sometimes used to prevent the explosion of the next round in a magazine when the gun recoils. Flat nosed bullets also have certain expansion properties that might make them desirable for close range combat.
References
µhttp://www.arizonagunlist.com/ammunition_types.html§
µhttp://www.midwayusa.com/content/legacy/bullet_composition.htm§