firearm

Firearm

Classification

CARTRIDGE

SANDIP KUMAR SINGHROLL - 124

1.SHOTGUN CARTRIDGE

2.RIFLE CARTRIDGE

SHOTGUN CARTRIDGE

BASE IT CONSISTS OF A METAL CYLINDER (brass) WHICH IS CONTINUOUS WITH A CARDBOARD OR PLASTIC CYLINDER

THE CASE IS RIMMED WHICH KEEPS THE CARTRIGE CORRECTLY IN THE CHAMBER AND FACILITATES EXTRACTION.

FILLING OF CARTRIDGE FROM BASE ARE :-

1. PERCUSSION CAP

2. GUN POWDER

3. FELT WAD WITH CARDBOARD DISC

4. THE SHOT

5. RETAINING CARDBOARD DISC

TYPES• GLAZED BOARD• STRAW BOARD• PLASTIC • CORK• FELT • ETC

WADS

SHAPE• DISC SHAPED

• CUP SHAPED

• BIZZARE SHAPED

WADS

THE DIAMETER OF WADDING USED IN THE CARTRIDGE IS GREATER THAN THAT OF THE BORE OF THE GUN.

WAD ACTS AS THE PISTON AND SEALS THE BORE COMPLETELY THUS PREVENTING THE EXPANDING GASES FROM ESCAPING AND DISTURBING THE SHOT CHARGE.

WADS

THE WAD CONTAINS GREASE WHICH LUBRICATES THE BORE AFTER FIRING OF EACH ROUND

THE GUN POWDER IS PROTECTED FROM GREASE BY THIN GREASE PROOF CARD WAD

WADS

THE SHOT CONSISTS OF SEVERAL HUNDRED SMALL LEAD SHOTS .

NUMBER DEPENDS ON :-

•THE SIZE OF THE LOAD

•SIZE OF THE INDIVIDUAL PELLET

SHOT

Gaffiers ( greener _rimengiton

_schnider

RIFLE CARTRIDGE

IT HAS A METAL CYLINDER WITH A FLAT BASE WHICH PROJECTS AS A RIM

RIMLESS CARTRIDGE HAS AN EXTRACTOR GROOVE NEAR THE BASE.

PRIMER CUP IS FITTED IN THE CENTER OF THE BASE

THE CARTRIDGE CASE IS ELONGATED AND ITS DISTAL END TIGHTLY GRIPS THE BASE OF THE BULLET

GUN POWDER•BLACK POWDER

•SMOKELESS POWDER

BLACK POWDER

•POTASSIUM NITRATE 75%

•SULPHUR 10%

•CHARCOAL 15%

BLACK POWDER •IT IS DESIGNATED AS FG,FFG,FFFG

•THE MORE NUMBER OF F’s , THE FINER ARE THE GRAINS AND THE FASTER THEY BURN

•IT BURNS WITH PRODUCTION OF HEAT ,FLAME AND SMOKE

•1 GRAM OF POWDER PRODUCES 3000 TO 4500 CC OF GAS

SMOKELESS POWDER

•THEY PRODUCE MUCH LESS SMOKE AND FLAME AND ARE MORE COMPLETELY BURNT THAN BLACK POWDER

• 1 GRAM PRODUCES 12000 TO 13000 CC OF GASES

•THE COLOUR VARIES FROM BRIGHT ORANGE TO BLUISH BLACK

Missile (projectile) (rifled )

BULLETSTHE TRADITIONAL BULLET IS MADE OF SOFT METAL AND HAS A ROUNDED NOSE .

THE METAL USED IS LEAD

THE MISSILE IS THE COMMON BULLET USED IN PISTOLS AND RIFLES.

IN PISTOL THE BULLET IS SHORT AND THE POINT IS ROUNDED

IN RIFLES THE BULLET IS ELONGATED AND POINTED

BULLETSJACKETED BULLETS ARE OF TWO TYPES :

1. FULL METAL JACKET BULLET

2. THE SEMI-JACKETED BULLET

FULL METAL JACKET BULLET

•COVERING IS MADE WITH TOUGH AND HEAVY JACKET COVERS

•BASE HAS SOFT METAL INTERIOR

•THE TOUGH METAL MAY BE MADE OF STEEL,ZINC,COPPER,NICKEL

SEMI-JACKETED BULLET

•IT HAS A TOUGH JACKET BUT THINNER COMPARED TO FULL METAL JACKET BULLET

•THE NOSE IS FULLY OR PARTLY EXPOSED

A DUMDUM BULLET IS ONE WHICH FRAGMENTS EXTENSIVELY UPON STRIKING

Missile (projectile) Non rifled

Wads (external _internal )

External Internal

Shots

Sporting gun Greener gun Schneider

MECHANISM OF DISCHARGE OF PROJECTILE

TRIGGER IS PULLED

FIRING PIN STRIKES THE PRIMER CAP

THE PRIMING EXPLODES

SENDS FLASH TO THE POWDER FILLED CASE

POWDER CHARGE BURNS

LARGE AMT OF GAS PRODUCED INCREASES PRESSURE

Firearm wound

CHARACTERS OF FIREARM INJURIES (WOUND)

1- Loss of substance This loss depends on the size of missile, velocity and distance of firing.

2- Presence of two wounds inlet and exit (grazing of the bullet)

3- Possible presence of associated of projectile (Powder marks)

4- Beveling occurs in flat bones .

DIFFERENCE BETWEEN INLET & EXIT

exit inletLarge Small Size

Less More Loss of substance

NO ++++ Powder marks

Everted Inverted Edge

Eternal Internal Beveling

Factor affecting the shape of the FA wound

1- The type of the weapon 2- Distance of firing 3- Direction of firing. 4- Site of the wound 5- Type and amount of the powder

Estimation of the distance of firing:

1- In cases of short distance (near firing):Powder marks

II- In cases of long distance (far firing):• The estimation of distance is based on the extent

of dispersion of shots• In cases of bullets it is estimated by the amount of

penetration

point blank firing (0-15)

• The inlet is cross shaped• Everted• Burnt (flam).• Blackening (smoke)• Tattooing (unburned particles).

In contact firing

• Burning take the shape of the muzzle,

• Minimal blackening and tattooing.

Why

Medico legal importance of powder marks:

1- Diagnosis of fire arm injuries

2- Differentiation between inlet and exit 3- Identification the type of powder used

4- Estimation the distance of firing 5- Determination the direction of firing

Identification of the weapon used

• Finger prints• Smell of burnt powder • Type and bore compared with projectile

extracted form the victim• Experimental examination of the suspected

weapon • Empty cartridge at the scene of the crime

Suicide , homicide or accidental

1. Circumstantial evidence

2. Scene of the crime

3. Examination of the victim • Sex - Victims clothes - Cadaveric spasm • Blackening of the victim's fingers • Signs of resistance

4- Examination of the wound • Site of the wound• Number of wounds • Distance of firing

5 -Examination of the weapon• presence of the weapon• Type of weapon Short – long

6- Examination of the suspected assailant

Entrance Wounds

1. Shotguns:

- The mass of shot leaves the weapon initially as a solid mass, which progressively diverges from the weapon.

Contact Wounds (touching the skin)

- When a weapon is fired, the bullet, hot gases from exploding gun powder & metal fragments from the bullet & the gun barrel are propelled out of the muzzle at the same time.

- The hot gases & metal fragments are blasted into the body at the same time as bullet.

Contact Wounds cont.

- Round or oval central defect with an ‘abrasion collar’ (where the bullet has abraded the skin surface as it passes through it). The size of the defect is comparable to the size of the muzzle opening or bore of the weapon.

- “Pink/red” staining of the skin (due to carbon monoxide laden gases producing carboxyhaemoglobin)

- Gun powder blackening of the wound edges & surrounding skin (from soot & unburned propellant gases).

-Circular bruise over the skin due to muzzle impact.

Contact Wounds cont.Summery

-Wounds are circular

-There may be muzzle mark

-There may be a slight local burning to the skin & hair

-Redness from CO gases

Contact Wounds cont.

Muzzle imprint

Burning from the powder

Near Discharge - Within few cm of surface

-Large central defect with ‘stippling’ or ‘tattooing’ ( small, dry, reddish abrasions caused by unburned powder & small metal fragments striking the skin)

- Smoke soiling

- Lack of muzzle mark tattooing

Intermediate Range Intermediate Range

Intermediate Range -Within 20 cm to 1 m.

- Diminishing of the smoke soiling but powder tattooing persist

- Burning will be present

- The rim of the wound is irregular forming what is called ‘rat-hole’.

Intermediate Range

Long Range (2-3m) -Satellite pellet holes will be seen around the central wound, which diminishes in size as the range increases.

- the spread of shot in centimeters equal two to three times the range in meters.

e.g. if the wound pattern is 20 cm across the discharge was roughly 7 – 10 m so couldn’t be a suicide.

Long Range ( 20 – 30 m)

-Abrasion collar

-No smoke soiling, burning or powder tattooing.

-Tissue displacement.

-Rarely fatal.

Differences between shotgun & rifles in entrance wound

Rifled weapons:

- show increased amount of tissue destruction due to the high velocities involved.

-Usually have an entrance and exit wound unless bullet has struck a bony area such as the skull.

-Estimation of firing range is more difficult than with shotgun weapons, but in general , contact wounds show similar features of powder stippling, blackening, burning, tissue disruption, & carboxyhaemoglobin formation.

Exit wound

-Shotguns: Rarely produce exit wound because they traverse the body, but if happened it may cause a huge ragged aperture wound.

-Rifled weapons:

--Exit wound is usually everted with split flaps.

--No burning, smoke or powder soiling.

--if the bullet flattened or has destruct some bone internally, exit wound may be more irregular and sometimes very large in size.

Exit wound

Entrance Wound

Exit Wound with split flaps

Exit wound

Accident, Suicide, or Murder

-Suicides must show wounds which range within the arms reach unless some devices is present to reach the trigger.

-Suicides shoot themselves in sites of election which include the mouth, the front of the neck, the forehead, or the front of the chest.

-Discharge into the entrance wound are usually on the side of the dominant hand, but this is not absolute.

-People almost never shot themselves in the eye or abdomen & naturally not in inaccessible sites such as the back.

-Women rarely commit suicide with guns & rarely involved in firearm accidents.

Accident, Suicide, or Murder

-‘A shot woman is a murdered woman until proved otherwise’.

-Multiple firearm wounds suggest homicide, but this is by no means inevitable.

-It’s unwise to state that a gunshot wound must have been immediately fatal, unless destruction of brain stem or heart or transection of the aorta has occurred.

-There are many instances of gross brain damage, especially in the cerebrum, bring followed by prolonged purposeful activity.

-In suicide weapon must be present, though it may be at a distance from the body.

Doctors duty in firearm injuries & deaths

-Any missile, foreign body such as wads and any skin removed from the margin of a repaired firearm wound should be carefully preserved for the police.

-The skin in post-mortem examination around the entrance wound should be removed & kept without formalin, but refrigerated if necessary, for forensic tests for powder residue.

-In many countries firearm injuries must be reported to the police even if not fatal.

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