Forensic Ballistics Exam - Categorizing Bullets
It is the responsibility of a forensic firearms examiner to asses the physical and chemical makeup of a bullet in order to determine its manufacturer and narrow the list of weapons that are suspected to be used in a crime such as murder. One can find most bullet types in firearms of different calibers and muzzle velocities. However, softer bullets such as lead are prevalent in low-velocity firearms, whereas harder or jacketed bullets are usually used in high-velocity weapons.
Bullets can be classified in one of four (4) categories:
* Lead bullets–These bullets are soft and typically used in low-velocity weapons like small-caliber .22 and .25 handguns and rifles. These bullets are most likely to change shape and fragment upon hitting a target. They have the least amount of penetration yet the deformation and fragmentation of the projectile can cause major soft tissue damage.
* Lead alloy bullets–These bullets contain lead and small amounts of one or more other metals that make them harder. Antimony and tin mixed in with lead are created for bullets intended for high-velocity weapons. Because of their increased hardness, these projectiles are less inclined to change shape and fragment yet more inclined to penetrate deeper into the target.
* Semijacketed bullets–These bullets have a thin layer of brass covering their sides. The nose of the bullet is exposed and is made of soft lead, allowing the bullet to expand and separate on impact. The exposed nose may be slightly hollow, hence a hollow-point bullet, which is the kind that changes shape and fragments even more causing a greater amount of tissue damage in the person that it hits. These bullets are used in low-velocity firearms as well as higher-velocity ones such as .357 and .44 magnum handguns and high-powered rifles.
* Fully jacketed bullets–These bullets are covered with brass including the tip. Also known as full metal jackets, these projectiles are usually intended for use in high-velocity firearms, such as .44 magnum handguns and high-powered rifles. They have the deepest penetration than other bullets, and instead of brass, can be coated with Teflon, nylon, and other man-made materials. These materials are hard and slippery, acting as lubricants that contribute to very high muzzle velocities and a high degree of penetrability. Many full metal jackets are armor-piercing bullets and thus are known as cop killers.