Topic 4: Cartridge Case Flashcards
It is the part of the cartridge which houses the bullet, gunpowder, and primer.
CARTRIDGE CASE/SHELL/CASING
This part has a significant contribution to the identification of firearms because it receives the individual characteristics from the firearm where it was fired, extracted, and ejected. Moreover, this is commonly recovered at the crime scene unless the firearm used is a revolver. In a revolver, the cartridge remains in the chamber of the rotating cylinder. The other term for cartridge cases s casing or shelf
CARTRIDGE CASE/SHELL/CASING
PARTS OF CARTRIDGE CASE
Rim
Primer pocket
Vent or Flash hole
Body Gunpowder
Neck
Cannelure
Base
Dhoulder
Extracting grove
-Located on the base of the cartridge case and is responsible for limiting the forward movement of the cartridge when loaded in the chamber of a revolver or shotgun. In automatic firearms, which are loaded with semi-rimmed and rimless cartridges, their function is to facilitate the ejection of the cartridge case from the firearm
Rim
The hole at the center of the base of the cartridge is designed to house the primer. When a primer is removed or loosened, the gas will leak through this opening. Hence, the manufacturers would design a cartridge so that the primer is precisely fitted to this hole
Primer Pocket
- The hole located at the center of the primer pocket serves as the canal of the ignition produced by the primer towards the gunpowder.
Vent or Flash Hole
is contained in this part. In order to develop sufficient pressure, the heat should not be able to escape during an explosion. This part also receives the chamber markings. The markings are created after the explosion because the explosion causes it to expand and make direct contact with the chamber of the gun.
Body Gunpowder
- This part is occupied by the bullet in a bottleneck cartridge case and where the cannelure is located.
Neck
- It is also a serrated groove located inside the mouth of the cartridge case, which aids the cannelure in holding the end portion of the bullet.
- Crimp
- It refers to the hardest part of the cartridge located in the rear portion. It contains the rim. and primer.
- Base
- A serrated groove found at the neck holds the bullet’s end part. It prevents the bullet from being pushed back or loosened.
Cannelure
It is also the part where the caliber and the manufacturer’s name are engraved. It is significant in firearm identification because it receives the breech face markings. It is created when the cartridge case is extracted out from the chamber and pulled back towards the breech face.
- Base
This refers to the serrated groove located between the cartridge case’s body and base. This part receives the extractor marks. It is created when the hand of the extractor drags this part to withdraw the cartridge case out from the gun chamber.
- Extracting Groove
CLASSIFICATION OF CARTRIDGE CASE ACCORDING TO CASE SHAPE
Straight cartridge case
Bottle neck cartridge case
Tapered cartridge case
This is a part of a bottleneck cartridge case located between the body and neck.
- Shoulder
- It is straight from the rear portion of the body towards the mouth Designed to accommodate the standard amount of gunpowder as well as the caliber of bullet of the pistols and revolvers. Also, this is intended to fit in the chamber of the said firearms.
- Straight Cartridge Case
- The diameter of its body is greater than the diameter of its neck and mouth It is constructed so that a greater amount of gun powder is accommodated. A common example is the 5.56 mm rifle cartridge case,
- Bottle Neck Cartridge Case
- Its design is tapered towards the mouth. It was used in a magnum jet cartridge case of caliber 22 centerfire. It is no longer used today.
- Tapered Cartridge Case
The tim diameter is much bigger than the body of the cartridge case and the diameter of the chamber of a revolver and shotgun. It is designed so that the cartridge will not move forward after it is loaded in the chamber of the said firearms.
- Rimmed Cartridge Case
This is appropriate for a semi-automatic weapon like 9mm pistol. The diameter of its rim is a little bit bigger than the body. However, it is a little bit smaller than the diameter of the chamber of the said firearms. As such, its rim does not serve to limit the forward movement of the cartridge upon loading in the chamber
- Semi-rimmed
It is commonly subjected to misconception due to its term. However, it has a rim, but its diameter is equal to the body of the cartridge case. It is commonly used in automatic rifles and pistols because it is precise for the cartridge’s smooth feeding to the chamber.
- Rimless
The diameter of the rim is a little bit smaller than its body. It is commonly used in caliber 40 Smith and Wesson design.
- Rebated
The rim is belted around the body of the cartridge case. It is designed to fit in the chamber of a magnum rifle.
- Belted
MARKS ON A FIRED CARTRIDGE CASE
Firing pin marks
Breech face marks
Chamber marks
Shaer marks
Extractor marks
Magazine lips marks
Enjector marks
- It is a marking located on the primer of the cartridge case. It is produced when the firing pin strikes the primer.
- Firing Pin Marks
- This mark is found on the base of the cartridge case. It results from the contact between the breech face of the firearm and the base of the cartridge case. The contact occurs since the breech face of the gun is positioned next to the chamber where the cartridge case is loaded. Thus, the moment the cartridge case is withdrawn from the chamber it will hit the breech face.
- Breech Face Marks
It is a marking striated on the body of the cartridge case. After the combustion of gunpowder, heated gas is produced and expanded. This further resulted in the body of the cartridge expanding. Thus, it comes in contact with the wall of the chamber. The impact between the two resulted in the softer one receiving the scratches. These scratches are called chamber marks.
- Chamber Marks
- These marks are impressed on the primer resulting from the collision between the breech face and cartridge case after it is pulled back by the heated gas. Since the point of the firing pin still elevates in the hole located at the center of the breech face, another contact between the primer and the said portion of the firing pin will occur. However, the mark produced is shallower than the firing pin mark.
- Shear Marks
- These marks are caused by the tool of the firearm called an extractor. It is located on the extracting groove of the cartridge case.
- Extractor Marks
is attached on the bolt which is positioned in a way that it hooks the extracting groove of the cartridge case. By the time the bolt moves backward, the cartridge case will also be dragged by the extractor backward.
- Extractor Marks
- These are markings of two parallel lines on the rim or the body of the empty shell.
- Magazine Lips Marks
cause these marks during the loading and dragging of the cartridges by the slide from the magazine to the chamber of the firearm for firing.
Magazine lips marks
- These are found on the rim of the cartridge case. These are produced during the contact between the rim of the cartridge case and the ejector. The said contact occurs when the cartridge case is drawn to the rear portion of the firearm where the ejector is positioned.
- Ejector Marks
