Physical Features

Most modern bullets fall into two categories:

• Plain lead bullets ( swaged or cast)
• Jacketed bullets (heavy core enclosed by an outer jacket of gilding meta(heavy core enclosed by an outer jacket of gliding metal)

Within these two categories, there are a wide variety of bullet designs intended to improve performance for a particular purpose.

Terminology

Characteristics

The categories of physical features of bullets are extensive and can be used to search reference materials for bullets with similar features.

The primary physical features of bullets include these:

• Weight
• Measured caliber/diameter
• Composition
• Jacket type
• Magnetic properties
• Length
• Color/finish
• Base construction
• Base shape
• Nose construction
• Nose shape
• Cannelures

Weight

The weight of a bullet is normally measured in grains using a balance. There are 7000 grains per pound or 437.5 grains per ounce.

The weight of a relatively intact bullet is a partial indicator of the type(s) of cartridge that may have contained the bullet. Weight is one of the factors used to determine cartridge type(s).

In the following chart, the weight of a bullet in grains corresponds to possible cartridge type(s). A bullet weight may overlap several cartridge types, indicating that more data are needed to narrow the field.

Considerations

When obtaining the remaining weight of a fired evidence bullet, the examiner should bear in mind the following considerations:

• Laboratory safety protocols should be followed.
• Laboratory trace evidence policies should be followed prior to and during removal of any material adhering to a bullet.
• Bullets should be cleaned so as to not damage the surfaces potentially bearing microscopic marks.
  • Soak in a mild detergent to loosen any adhering material. Gently scrub using a soft bristled toothbrush.
    
    -and/or-
    • Use an ultrasonic cleaner and appropriate fluid.
      • Follow the manufacturers recommendations.
      • Treat one bullet/fragment at a time.
      • Monitor and observe bullets during treatment; ultrasonic cleaning may alter the microscopic details on the surface of a bullet.
    • Use appropriate tools to mechanically remove debris (e.g., embedded wood particles, bone, cartilage).
• Weigh each bullet fragment separately because they may or may not originate from a single bullet. Individually weighed fragments can be regrouped later, if necessary.

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