Examination

The following preliminary steps in the examination of all firearms should be sequenced according to laboratory protocol and be documented:

1. Ensure that the firearm is unloaded.
2. Determine the brand and model.
3. Determine caliber designation.
   1. Measure the bore diameter.
   2. Measure the chamber, if possible.
   3. Research the type of design.
   4. Determine the country of origin. (Many of the older bolt-action rifles were manufactured for various countries, each of which used a different type of military ammunition).
   5. Obtain the cartridge dimensions by casting the chamber, if necessary.
4. Determine the action type.
5. Determine the safety type.
6. Determine if any modifications or alterations have been made.
   (AFTE Journal can be searched by keyword)
7. Observe anything else unusual about the firearm.
8. Note the type of sighting system and any accessories present.
9. Examine the bore (interior of the barrel) and determine class characteristics (number of lands and grooves and direction of twist).
   1. Examine the interior of the bore to ensure it is free of projectiles.
   2. Check the bore for the possible presence of biological material or gunshot residues. If biological residues are present, notify the proper laboratory section.
   3. Check for bulges or damage to the bore.
   4. Examine the chamber and/or forcing cone area for damage or cracking.

In addition, all firearm examinations include testing the trigger pull, the safety feature, and test firing of the mechanism.

Read a sample forensic worksheet and report - Firearms

 

Revolvers

Based on findings from the preliminary examination, proceed with the examination of revolvers as follows:

1. Remove the cylinder (for double-action revolvers, open the cylinder).
2. Inspect the cylinder for damage and smoke halos (may indicate which cylinder was fired last).
3. Replace (in double action, close) the cylinder and check the functionality of the cylinder stop.
   1. Cock the hammer until it locks and attempt to rotate the cylinder. (The cylinder stop located in the frame below the cylinder should hold the cylinder in alignment with the barrel.) Perform this check on all chambers.
   2. Manually hold the hammer to the rear while the cylinder stop is checked (double action only (DAO) revolvers).

1. Test the trigger pull. Click to view trigger pull section.
2. Test the safety functions. Click to view safety section.
3. Test fire the firearm. Click to view test fire section.

 

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