1. What are They and What can They Tell the Investigator?
Cartridge Head Stamps
What are They and What can They Tell the Investigator?

2. What are head stamps? "A cartridge head stamp is
a mark, or series of marks
impressed, or sometimes
embossed, on the head of
the cartridge case during its
manufacture. The mark can consist of numbers, letters, trademarks, figures or any combination of these. Systems of head stamp markings are used worldwide."

3. VOCABULARY
BULLET: The projectile.

4. Primer The ignition system for the propellant.
A high explosive that reacts upon impact. It produces a flame that travels through a hole in the base of the cartridge and ignites the propellant. (Gunpowder)

6. Propellant
Propellant – A chemical compound which, when ignited, produce a high volume of gases. Gunpowder is another term frequently used for propellant.

7. Fill in the Blanks

8. Answer

10. Head Stamp

11. What Kind of Information Is on the Head Stamp?
In this case
The brand name
“Blazer
“The Caliber
.40 or 40/100”
The brand of
firearm it was
designed for.

12. Standard Head Stamp Information on Civilian Ammunition
caliber of the bullet
the brand name of the cartridge.
If the head stamp has the letters "mm" stamped on it, the caliber is measured in millimeters. A 9 mm bullet is 9 millimeters in diameter.
If the head stamp does not have “mm” on it, then the caliber is in inches.

13. These are calibers that have been used primarily by the United States and United Kingdom. An example would be ".357" means that the diameter is approximately 357/100th of an inch. However If you see that the number is "45” it does not mean that the diameter of the bullet is 45 inches. That would be almost 4' across. It just means that the manufacturer didn't bother putting the decimal point into the head stamp. The diameter is approximately 45/100th of an inch.

14. This head stamp, for example, was made by Remington Arms. It is a
This head stamp, for example, was made by Remington Arms. It is a .45 caliber cartridge originally designed for a Colt firearm. That means that it is approximately 45/100ths of an inch in diameter.

15. Additional Numbers May be present on the head stamp.
For example, “0.45–70–500.” In this case the caliber is .45", there is the equivalent of 70 grains of black powder propellant in the cartridge, and the weight of the bullet (projectile) is 500 grams.
This is not, however, consistent.

16. For Example
30-06 is a .30" caliber bullet, but it was introduced in 1906.
It is necessary to have
reference materials
available in order to
insure that you are
accurately interpreting
the head stamps.

17. Magnums
“Magnum” or “Mag” on the head stamp means that the cartridge has additional propellant and will provide greater pressure when it discharges. This will push the bullet to a higher velocity but will increase the stress on the firearm.
An example would be the .38 and the .357 magnum. The .38 actually has a diameter of .357" so they are the same basic bullet, however, the shell casing of the .357 is longer than the .38 and contains more propellant. A shooter can place a .38 cartridge into a .357 magnum revolver and fire the weapon without problem. The shooter cannot put a .357 cartridge into a .38. It is too long. This is fortunate, because the .38 weapon is not designed to handle the stress of a magnum round. The weapon's cylinder or barrel could fail and injure the shooter.

18. .357 v .38

19. “Auto” or “ACP”
The head stamp may also contain the word "Auto" or the initials "ACP". "Auto” refers to the type of weapon it is designed for, either a semi-automatic or fully automatic. "ACP" means substantially the same thing. It stands for "Automatic Colt Pistol." (The "Automatic Colt Pistol" however, is actually a semi-automatic weapon.) ACP rounds are not limited to being used in Colt pistols, it is merely their designation.

20. Military
The head stamp on military ammunition may have a great deal more information. The military has to track and distribute millions of rounds to its soldiers. If a batch of 5.56 NATO ammo has defective primers the military needs to be able to recall that ammunition specifically rather than all of the Military ammo head stamps may therefore, may contain information about the caliber, month and year that the ammo was made, the batch number, what the shell case is made of, what type of bullet it contains and any special characteristics of the bullet. For example, is it a tracer round, armor piercing or incendiary.

21. Any alphabet, language or set of symbols may be used by the manufacturing country. Each country will usually have a set of format rules for the head stamp of its military ammunition. These patterns can help identify the country of origin even when the information itself is not readily understood. Reference material is required by the investigator to make sure of what the head stamp says.

22. For Example

23. Interesting Notes About Cartridges
When a revolver is used in a crime, the cartridge will not be found at the crime scene unless the suspect opens the cylinder and dumps the cartridges.
When a semi-automatic or fully automatic firearm is used the expended cartridges are automatically ejected. Usually the trajectory of the ejected cartridge is to the right of the shooter, provided some other condition such as a wall or other barrier does not interfere.

24. Notes Continued
When a cartridge is fired it travels backwards with the same kinetic energy the propels the bullet forward. When the shell casing slams into the breech in the chamber, the head of the cartridge can receive an imprint from any defect that appears in the breech face. An image of the head stamp may also be transferred into the dirt and oil on the breech face. In these cases the breech face will show the image of the last cartridge fired. This can be photographed by the lab provided they do not clean the weapon first.

25. In Summation
In summation, head stamps are widely used and convey a great deal of information but there is such a wide variation of symbols, designs, and formats that investigators should devote time to learning the systems and have ready access to reference material to insure accurate decoding of the information.