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Ballistics

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saffa abd el aziz

on 15 December 2015

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Transcript of Ballistics

Ballistics
By:
Saffa Abd El Aziz
Assistant lecturer in the department of forensic medicine &clinical toxicology

Signs of firing on a cartridge.

Firing pin marks.

Signs of firing on a bullet.
Primary rifle marks.
Secondary rifle marks.

Secondary rifle marks.
They are irregular scratches on the surface of fired bullet.
Caused by defects or irregularities in the barrel of the gun or in its muzzle.

What is rifling ?
It is a number of parallel but spiral lands (projecting ridges) and grooves (depressed spirals between the lands) on the interior of the barrel from the breech to the muzzle.

Definition
and
Classification
DEFINITION:
It is the science that studies the motion of a projectile (Projected from a firearm weapon).

Anatomy of the Gun

Classification of firearm weapons:
According to the length of the barrel:

1) Long barreled (Rifles) e.g: service rifle (automatic & non automatic.)

According to the number of projectiles:

Single missile firing (bullet) e.g: service rifle, automatic
pistol & revolver (old, new).

According to the inner surface of the barrel:

1- Rifled weapons e.g: service rifle (long barreled), automatic pistol, revolver (short barreled).

2- Non rifled weapons(smooth bore weapons) e.g: sporting gun.

2. short barreled (hand guns)
e.g: pistol (automatic),
revolver(old, new)

Multiple missile firing(shots or pellets) e.g: sporting gun.

Functions of rifling:
1. Spiraling motion of the bullet which leads to:
- Increase distance of firing.
- Increase power of penetration.
2. Gyroscopic steadiness.
3. It helps in identification of the weapons as it differs from one weapon to another according to:-
1- Number of lands and grooves.
2- Direction of twist (clockwise or anti-clockwise).
3- Width of lands and grooves.
4- Depth of the grooves

So it is considered as family characteristic.


Ammunition
Ammunition
Bullets
Sporting gun
(non rifled, multiple missile firing)
for rifled weapons
for non rifled weapons
Is a cartridge that consists of a case
and a bullet (projectile).

Service rifle
The case:
*Long, narrow &it has a shoulder.
*Made of brass.
*In automatic SR: the base is grooved.
*In non automatic S.R: the base is rimmed.

From the bottom:
The base contains the percussion cap.

Mechanism of firing
Contents of the complete cartridge:
1.The primer(igniting powder)

It is the paste that lines the percussion cap


2.propellant powder:

-It is the actual source of energy.
-The pressure of a compressed gas
acting on the base of the projectile is the necessary propelling force.
-So propellant powder must be:
1. easily combustible.
2. release great quantity of gas on combustion.


(long barreled, rifled, single missile firing)
Short barreled
rifled weapons
Automatic pistol (automatic),
Revolver(old or new), nonautomatic.

The Case:
*Short, narrow and it has no shoulder.
*Made of brass.
*In automatic pistol, the base is grooved.
*In revolver(old and new), the base is rimmed.

Initially, mercury fulminate replaced by a combination of chemical compounds (lead, barium and antimony) which play an important role in detection of GSR.
Nowadays, lead-free primers are also available (e.g., “Sintox” with the main elements zinc and titanium). This is to avoid the injurious effects of lead on environment.

According to their composition:
- Solid (Non Jacketed bullet , homogenous):
- Jacketed
Long with pointed tip or
sometimes dome shaped
(rounded).

it is fully jacketed

service rifle
Short and dome shaped.
*automatic pistol: fully jacketed.
*revolver: may be
jacketed (new revolver),
or non jacketed (old revolver).

Hand gun
ammunition is cartridges (shells) Consists of a base made of brass and an upper part made of cardboard or plastic.


The centre of the base contains the percussion cap which is lined by the igniting powder (primer).
Above the base, a space is filled by
the
propellant powder,
then the
inner wad
,
followed by the
pellets
(shots) and lastly
the
outer wad.

• Pellets (Shots):
- They are rounded, small in size and made of lead.

Inner wad:

Thick, disk shaped.
Made of felt, cardboard or plastic.

-
Functions of Inner wad:
1- Separates propellant powder from shots.
2- Acts as a gas seal by preventing the escape of gases between the shots.
3- Acts as one of the shots producing damage (penetrates the body at 3 meters, hits the body causing rounded abrasion or bruises up at 10 meters)
4- It helps in estimation of distance of firing.

5- Helps to identify the weapon and its type.
6- Cleans the barrel as it passes through.
7- Leads to a smooth acceleration of the whole load of shots.

Outer wad:

Thin disc shaped.
Made of plastic or cardboard.

Functions Outer wad:
1. Keeps shots from falling.
2. Acts as one of the shots producing damage (penetrates the body at l meter, hits the body causing circular abrasions and bruises up to 3 meters).
3. Helps in estimation of distance of firing.

plastic cup.
Nowadays the inner and outer wads are replaced by a plastic cup.
The Function of which is similar to the inner wad, but it can produce lacerations. (because it has wings) and the distance is from 2-5 m.


Types of propellant powder
Black powder
Carbon, sulfur, potassium nitrate.

Irregular black clumps or fine smooth powder.

Sporting gun, old Revolver

One volume produces 1300 ml volumes of gases.

Alkaline residue of carbonates and bicarbonates

Blackening within and around the inlet


Smokeless powder

Single-base powder: nitrocellulose
Double-base powder: NC dissolved in nitrogycerine
Triple-base powder: nitrocellulose, nitroglycerine and nitroguanidine

Different but uniform shapes, colors and sizes.

Sporting gun, Rifled weapons except old revolver.

One volume produces 13000 ml volumes of gases

Neutral residue of nitrites and nitrates


Grayish color

signs of firing
Primary rifle marks.
Longitudinal parallel oblique grooves on the surface of the fired bullet resulting from rifling inside the barrel equivalent to them as regards their number, depth, width& direction of twist.
Caused by the rifling of the gun when the bullet travels through the barrel.

Family characteristic
or rifling characteristic of bullets can give clue to the manufacturing and model of the firearm weapon from which they were fired.

Seen by
naked eye
.

Only screening
not confirmatory.

They are considered
confirmatory marks
that act as a signature of the used gun on the fired bullet.
They form the

individual characteristics
of the barrel.
Seen only by
comparison microscope.

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