Archived | Firearms Examiner Training | Composition

Composition

Bullet composition refers to the materials used in the fabrication of a bullet.

Basic types of compositions include the following:

Solid Bullets.
- Swaged and cast lead.
- Single metal (e.g., steel, aluminum, zinc, copper alloys, and brass).
Bullet Jackets.
- Jacketing metals (e.g., copper alloys, brass, aluminum, nickel, and steel).
Bullet Cores.
- Heavier metals (e.g., lead and steel).
Bullet Coatings.
- Coated / washed / plated copper, brass, nylon ( Nyclad), Teflon.
Sabots.
- Plastic sleeve or adaptor surrounding a subcaliber bullet that allows it to be fired in a larger caliber firearm. The projectile never directly touches the barrel, and the sabot typically falls away after firing. Because the bullet never directly engages the barrel, rifling impressions will not be impressed on the bullet but rather the sabot.

Core and jacket Courtesy of Ronnie Freels (see reuse policy).	Bullet coatings Courtesy of Ronnie Freels (see reuse policy).	Federal nyclad Courtesy of Ronnie Freels (see reuse policy).
Teflon coated Courtesy of Ronnie Freels (see reuse policy).		Sabots Courtesy of Ronnie Freels (see reuse policy).

Jacket Type

Bullet jackets may be fabricated in a number of configurations:

Full metal jacket - encloses the entire bullet, with the exception of the base. Normally used for military purposes, these bullets are also known as full jacketed, full patch, full metal case , and ball ammunition.
Semijacketed partially encloses the bullet with the exception of an exposed soft point or a hollow point.
Total metal jacket fully encloses a bullet core.

Full metal jackets

Courtesy of Ronnie Freels (see reuse policy).

Remington semijacket hollow point

Courtesy of Ronnie Freels (see reuse policy).

Total metal jacket CCI Speer

Courtesy of Ronnie Freels (see reuse policy).

Properties

Bullet length

National Institute of Justice (NIJ) (see reuse policy).

Magnetic

To determine if a bullet is ferrous, a magnet can be used.

Length

Length information may be of limited value because fired bullets are slightly longer than unfired bullets. To ensure good obturation at the base of the bullet, bullets have a diameter slightly larger than the barrel through which they are fired. When the bullet is fired, it is lengthened by extrusion. A general similarity between a fired evidence bullet and a reference standard is sufficient to establish a general consistency in length.

Note:

Damaged, mutilated, and deformed bullets may not yield accurate measurements.

Color and Finish

The color of materials used in bullet construction or the color of any coating may be helpful in searching reference files for a particular type of ammunition. Although there are many specialized color-coded bullets (generally of military origin), they are only occasionally or rarely found in forensic casework.

Examiners must be aware of bullet color coding because there are several safety implications. Coding conventions may differ between countries and even within a given country.

Examples include the following:

Armor-piercing bullets are designed to pierce metal. They usually contain a hardened core or are completely composed of a substance other than lead or lead alloy.

Exploding bullets contain a primer or other explosive and are designed to explode upon impact.

Frangible bullets are designed to disintegrate upon impact with a hard surface in order to minimize ricochet.

Incendiary bullets contain a chemical compound that ignites upon impact, starting a fire.

Tracer bullets contain a burning compound in the base to permit observation of bullet flight.

Military armor piercing Courtesy of Ronnie Freels (see reuse policy).	Winchester frangible Courtesy of Ronnie Freels (see reuse policy).
Incendiary (military) Courtesy of Ronnie Freels (see reuse policy).	Tracer bullets Courtesy of Ronnie Freels (see reuse policy).

Back Forward

Additional Online Courses

See additional NIJ-sponsored training

Date Created: July 12, 2023