Some bullet designs impact the ability to find and evaluate microscopic marks, including the following:
- Coated bullets are lead alloy bullets with a thin coating of another substance (not a jacket).
- Nyclad is an inert nylon coating. While this type of bullet will have impressions on the bearing surface after firing, they are typically less well defined and more difficult to measure.
- Copper or brass plated/washed bullets are covered with a thin alloy coating that can make reading dimensions more difficult because of their propensity for peeling.
- Teflon coated bullets retain very little microscopic detail of value for comparison purposes.
- Exploding bullets contain a primer or explosive and are designed to explode upon impact, resulting in an unreadable bearing surface.
- Frangible bullets are designed to disintegrate upon impact with a hard surface to minimize ricochet. No measurable bearing surface remains.
- Sabots are lightweight collars that allow smaller, lighter bullets to be fired. Microscopic marks are found on the sabot but not on the bullet.
Reloaded and Handloaded Bullets
Bullets that are handloaded into new or used cartridge cases using a reloading press are in effect friction fit and sometimes crimped in the mouth of the cartridge cases. The force needed to do this is frequently provided by a reloading press. The bullet-seating tools used by the handloader may leave potentially unique and often identifiable microscopic marks on a bullet.
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