1. (Discussion and Continue Worksheet - Firearms)
Wednesday February 28, 2018
(Discussion and Continue Worksheet - Firearms)

2. The Daily CSI
Wednesday, 2/28/18
None Today!

3. Remediation for Quiz 12 runs through Friday!
Announcements
Remediation for Quiz 12 runs through Friday!

4. Summative or Formative # Hold for eResearch Paper
Assignment
Summative or Formative #
Date Issued
Gone Missing Day
Last Day Accepted
QUIZ 12 S3
2/26
Friday
WS – Firearms
F11
2/27
N/A
Hold for eResearch Paper

5. Firearms Projectiles

6. Shell Anatomy
Handgun and Rifle
Shotgun

7. Anatomy of a Bullet

8. Bullet Comparisons
Each gun leaves distinct markings on a bullet passing through it.
A gun barrel is made from a solid bar of steel that has been drilled/hollowed out.
The drill leaves microscopic marks on the barrel’s inner surface.

9. Bullet Comparisons
Gun manufacturers also add spiral grooves to the barrel. This is known as rifling.
Lands: the space between the grooves.
As a spinning bullet passes through the barrel, it is marked by these grooves.

10. Class Characteristics
Class Characteristics: Once a manufacturer chooses a rifling process, for a particular class of weapon, they keep it consistent.
Lands & Grooves are the same for a model.
.32 caliber Smith & Wesson has 5 lands & grooves twisting to the right.
.32 caliber Colt has 6 lands & grooves twisting to the left.
Class characteristics can eliminate certain makes but are not enough to ID a particular gun.

11. Individual Characteristics
Imperfections in the manufacturing process make each barrel unique.
Rifled barrels, even if made in succession will NOT have identical striation (scratch-like marks).

12. Bullet Comparisons
To match bullets to a gun, test bullets must be fired through a suspect barrel for comparison.
Comparison Microscopes
Examined bullets side-by-side (to match striated markings).

13. Bullet Comparisons

14. Cartridge Markings
All moving components contact the cartridge rather than the bullet can leave useful impressions on shell cartridges
Breechface marks
Firing pin impressions
Chamber marks
Extractor & Ejector markings

15. Breechface Marks

18. Actual Breech Marks

19. Firing Pin Marks

20. Chamber Marks

21. Ejector Marks

22. Other Factors Perfect matches sometimes difficult b/c:
Presence of grit & rust in a barrel
Recovered bullets too mutilated or distorted on impact
A spent bullet’s weight can sometimes determine the gun make.
Microgrooves: 8-24 grooves; it’s not as common
General Rifling Characteristics File
FBI database of known land/groove width for all weapons.

23. Shotguns Smooth barrel
Projectile NOT marked as it passes through
Fire small lead balls or pellets contained within a shell.
Characterized by:
diameter of the shot
size & shape of the wad
Gauge: diameter of the barrel
( gauge  diameter)

24. Continue Worksheet Firearms