Forensic analysis of ammunition

Question 1

Caliber and chambering

Answer 1

Ammunition size is described by caliber and chambering
caliber is the diameter of the projectile
Chambering refers to the length of the cartridge

E.g. 7.62 (calibre) * 39mm (chambering) = Russian AK47 military

Question 2

Caliber

Answer 2

the internal diameter of firearm barrel but is also used as the effective diameter of the bullet.

Question 3

Using the wrong ammunition

Answer 3

The round is too big and either won’t fit or jams in the battery
The round is too small and becomes loose

Too small of ammunition can cause pressure to come backwards up the gun towards you causing it to explode

Question 4

Headstamp

Answer 4

Most ammunition has a markers stamp on the base of the cartridge
This is known as the headstamp

Question 5

Cartridge case investigation

Answer 5

Examining the headstamp can reveal the caliber and could also provide manufacturers information

Question 6

Self-loading or single shot mechanism

Answer 6

Cartridge shape helps determine firearm type.
Self-loading firearms do not have protruding base rims beyond the main body of the cartridge case
Self-loading cases must have parallel sides to allow stacking in a magazine
Cartridges for single shot mechanisms such as in a revolver do have a protruding base rim
This stops the cartridge falling through the cylinder of the revolver and cases are extracted via a central web, so need a rim

The two are not interchangeable

Question 7

Cartridge case investigation 2

Answer 7

Phase 2 is to accurately measure all the dimensions of the cartridge
A micrometer is best for this with a digital vernier calliper a close second

Question 8

Class characteristics

Answer 8

General dimensions
Shape of firing pin mark
Primer type
Headstamp information

Question 9

Self-loading pistol components

Answer 9

Hammer
Slide
Ejection port
Muzzle
Mainspring cap
Frame
Trigger guard
Trigger
Grip safety
Magazine
Front sight
Rear sight
Slide lock
Magazine release
Grip panel
Thumb safety

Question 10

Typical cartridge marks

Answer 10

Slide drag marks
Ejection port dent
Slide scuff mark
Firing pin scrape mark
Firing pin impression
Chamber marks
Magazine lip marks
Extractor marks
Breech face marks
Ejector mark

Question 11

Shotgun ammunition identification

Answer 11

Will have a headstamp
Cartridge body material is likely plastic or card with a metallic head
Manufacturer data may be printed on the cartridge body
Headstamp is more reliable
Many suppliers print their own information on the cartridge