Abstract
The objective of this research was to determine the best casting material and method to cast fired bullets. In the
forensic firearms field, the comparison of fired bullets using a comparison microscope is the most useful way to match a fired
bullet to a particular firearm. Fired bullets can be traced back to the gun from which they were fired by careful examination
and comparison of the tiny scratches on their surfaces known as striations. These striations are used to compare a recovered
bullet from a scene to a bullet fired from a suspected weapon at the crime laboratory. Images of bullet striations can be
entered into the National Integrated Ballistic Information Network (NIBIN) and searched against known and unsolved
firearms cases in the database. Instead of sending the questioned bullet from one jurisdiction to another for comparison,
castings can be made. This allows one jurisdiction to keep the original evidence and maintain chain of custody, while still
providing assistance to another jurisdiction. Further, multiple castings can be made so multiple jurisdictions can conduct their
own analyses simultaneously.
The first casts were made with Mikrosil® and TRITECHFORENSICS Silicone Casting Material. The casts produced
were negative images of the bullets. This means that the striations on the cast were backwards and orientated the opposite
way of the bullet’s striations. Although the casts were negative images of the bullet, they still produced quality images of the
fired bullet. Since they are negative images of the bullet it is not possible to compare the casts with the bullet; only cast-to-
cast comparisons can be done. To combat this, a double cast was made by pouring Rio Grande® jeweler’s wax into the first
casts to make a wax bullet.
The striations on each land and groove of the fired bullet were counted. The striations on each land and groove of the
wax bullet produced were counted. The obtained average percent recovery was 85% for the lands and 82% for