Anatomy of Bullets

History

Metallic balls used in slings are considered to be the first bullets. As firearms were introduced to the world, bullets slowly became more advanced. Small lead balls, known as rounds, were used in the earliest firearms. The invention of the musket led to creation of cast lead balls. These lead bullets proved to be inaccurate from long distances.
The first pointed or cone shaped bullets were made in the 1800s. These bullets had hollow bases that expanded after firing so the bullet would connect with the barrel’s rifling, making it more accurate. The minie ball was the first popular pointed bullet; it was widely used in the American Civil War.
Minie Ball bullet.
Minie Ball bullet.
The modern bullet first appeared in the late 1800s. In the late 1882 the copper jacket bullet was invented. It had a long bullet with a lead core in a copper jacket. In the 1900s the spitzer bullet were invented. These bullets traveled faster and were more accurate over greater distances. Later on, the base of bullets was streamlined to reduce drag. The combination of a spitzer bullet with a streamlined base is basically the same shape of bullets used today.



Design

Bullets are a part of cartridges; cartridges hold together the bullet, case, propellant, and primer. The bullet is the actual projectile that applies force (hits) an object. Propellants, such as gunpowder, ignite and create pressurized gas inside the cartridge. The gas fills up the inside of the case, which leads to the explosion of the bullet. The primer, also known as the percussion cap, ignites the propellant after being hit by the hammer of the gun. Finally, the case is the metal tube that holds all of these parts together.
A catridge is made up of the (1) bullet, (2) case, (3) propellant, (4) rim, and (5) primer
A catridge is made up of the (1) bullet, (2) case, (3) propellant, (4) rim, and (5) primer


All bullets contain lead because lead has a good amount of mass, giving the bullet more kinetic energy. Faster bullets have a core that is covered in a metal jacket. This jacket allows the bullet to stay intact before hitting the target. Another factor affecting the impact characteristics of the bullet is the shape. One common shape is a round nosed bullet. Round nose bullets are bullets with rounded points. These bullets travel slower than more pointed bullets and usually only used for hunting purposes. Some
A hollow point bullet mushrooms to cause more damage and slow down so it doesn't penetrate too deep.
A hollow point bullet mushrooms to cause more damage and slow down so it doesn't penetrate too deep.
bullets are designed to expand upon impact creating a bigger cavity in the target. These bullets are known as hollow-point bullets and they most commonly used by police officers, as they do not penetrate as deep and they cause more tissue damage.


Another type of bullet is a full metal jacket bullet. This bullet is covered in a hard metal; this allows the bullet to remain whole so it can pierce a thin layer of armor. F.M.J bullets are typically used in the military as they can travel at high rates of speed and penetrate deep into the target.
Shotgun Shells are slightly different than regular bullets. They consist of a case, brass head, primer, powder, wad, and a shot or slug. The case, which is usually made of plastic, holds the shell together. The primer ignites the powder when it is struck by the hammer. The powder burns and creates a gas that pushes the shot or slug out. The wad separates the shot from the powder and it holds the shot together so that the shot stays together in the barrel and deforms less. The shot can be a slug, a single projectile, or multiple small projectiles. The shot is made from a variety of different metals.


Full Metal Jacket Bullet
Full Metal Jacket Bullet

Size is also an important characteristic of a bullet. Bullet size is measured by the caliber of the gun that they are used in. The caliber is the diameter of the bore of a firearm measured in hundredths of an inch. The bigger the diameter is the bigger the caliber is. For example, a gun that has a bore that is .50 inches in diameter is a 50-caliber gun. Larger caliber guns, such as a 50-caliber rifle, are a lot more powerful and lethal than smaller caliber guns.

Forensic Examination

In 1923, physicist John H. Fisher, chemist Philip Gravelle, and Charles Waite became the first people to create a lab devoted to Forensic Ballistics. The FBI crime lab first started comparing bullet fragments from crime scenes to unfired ammunition in the early 1980s.
An identification process known as comparative bullet lead analysis is used to connect the bullet fragments from a crime scene to the bullets in the suspect’s possession.By examining a bullet, one can determine the caliber, rifling impressions, and manufacturer of the bullet. The characteristics on a bullet from the crime scene can be compared with test bullets that are fired from the suspected firearm in order to find out from what gun the crime scene bullet was fired from.
As seen under a comparison microscope, the striations from a reference bullet match those of a crime scene bullet.
As seen under a comparison microscope, the striations from a reference bullet match those of a crime scene bullet.
It is nearly impossible for 2 firearms to leave the same exact marks on bullets and cases. Cartridges and cases are looked at for class similarities such as caliber and weight. If class similarities are not recognized than individual characteristics must be examined. Each guns barrel has imperfections that leave striations on the bullets. Striation patterns are unique for bullets fired from every gun.

Comparison microscopes are the most important tools for firearms examiners. This microscope allows examiners to view both the evidence bullet and a test-fired bullet from the suspected firearm in order to determine if both bullets have identical striation patterns. If the patterns are not identical examiners look at other individual characteristics such as firing pin, breechblock, extractor, and ejector marks. Bullet and cartridge characteristics are stored in computer databases so that computerized imaging can help find a bullet or cartridge with similar individual characteristics.

Timeline:

1918: Charles Waite catalogs the rifling of all gun models
1923: Charles Waite, John Fisher, and Philip Gravelle establish Bureau of Forensic Ballistics
1932: FBI establishes forensic lab, countries and cities follow
1980: FBI creates computer database of rifling characteristics
1992: FBI creates database of bullets and cartridge cases

Cases:

Commonwealth v. Best (1902) was the first court case that involved ballistic evidence. A gunsmith tested the suspected murder weapon by firing a shot into a bunch of cotton wool. He then compared the fired bullet to the one found at the crime scene using a magnifying glass and found that they matched.
One of the first, well-known forensic ballistics case was the St. Valentine’s Day Massacre. On St. Valentines Day in 1929, 7 men who were involved in hijacking alcohol from gangster Al Capone were lined up against a wall and shot (several times) to death. Once the bullets were removed from the bodies, the coroner’s office immediately called Calvin Goddard. Goddard was one the first scientists to create a ballistics database. Goddard helped determine that Chicago police officers were not involved in the murder. He did this by test firing their weapons and comparing the bullets to the bullets found at the crime scene. Goddard also proved that the machine guns that had been seized from one of the suspects were most likely the guns used in the murder.


References

"Bullet Construction Part 1- FirearmsID.com." FirearmsID.com- An Introduction to Forensic Firearm Identification. Web. 2 May 2011. <http://www.firearmsid.com/Bullets/bullet1.htm>.
FBI Handbook of Crime Scene Forensics. New York: Skyhorse Pub., 2008.
McGrath, Jane. "MythBusters: HSW Explainer : Discovery Channel." Discovery Channel : Science, History, Space, Tech, Sharks, News. Web. 12 May 2011. <http://dsc.discovery.com/fansites/mythbusters/articles/how-a-bullet-works.html>.
Ramsland, Katherine. "All about Ballistics in Solving Crimes, by Katherine Ramsland — The Bullets of Valentine's Day — Crime Library on TruTV.com." TruTV.com: Not Reality. Actuality. Web. 16 May 2011. <http://www.trutv.com/library/crime/criminal_mind/forensics/ballistics/2.html>.
Yount, Lisa. Forensic Science: from Fibers to Fingerprints. New York: Chelsea House, 2007.