Bullet Examination

Any weapon with a rifled barrel has lands and grooves that are necessary to impart spin on the bullet to improve accuracy over distances. However, these lands and grooves will also leave markings on the projectile.  The striations are linear and can appear at an angle due to the rotation within the barrel of the weapon.

Weapon manufacturer's use a rifling tool that cuts each barrel a little differently. This accounts for a variation between weapon to weapon and also individualizes the striation mark left on a bullet. Ultimately, bullets fired from the same weapons will have similar markings, while bullets fired from a separate weapon will not match.

With this in mind, shot guns do not have rifled barrels. They fire a wad of individual pellets so striation comparisons are not useful. The size of the shot is also not useful to determine the gauge of the shotgun.