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Firearm Injuries

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It is the science of motion of projectile.

Or

The study of various physical forces acting on the projectile is known as ballistics.

BALLISTICS:

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Internal ballistics. External ballistics. Terminal ballistics. Forensic Medicine.

Types of ballistics

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The study of various forces acting on the projectile, when it is moving in side the barrel of the fire arm weapon.

INTERNAL BALLISTICS / INTERIOR BALLISTICS:

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The study of various forces acting on the projectile, when it moves in the air from the barrel to the time of reaching the target.

Forces of medium – air resistance, gravity.

EXTERNAL BALLISTICS / EXTERIOR BALLISTICS

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It is the study of the effect of a bullet/shots on the target till it comes to rest, resulting in wound formation (wound ballistics).

TERMINAL BALLISTICS

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It is also known as firearms identification.

It deals with examination of fired bullets & cartridge cases and their identification as have been fired by the particular gun to the exclusion of all others.

FORENSIC BALLISTICS

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BASICALLY THE FIRE ARMS ARE CLASSIFIED IN TO; SMOOTH BORED FIRE ARMS . SHOT GUNS.GROOVED FIRE ARMS.i) RIFLES.ii) REVOLVERSiii) PISTOLS.

AIR GUNS

Classification of firearm

CLASSIFICATION OF FIREARMS1. SMOOTH BORED FIREARMS:

Breech loadingMuzzle loading

2. Single barrel Double barrel

According to the muzzle velocity: 1. low velocity (up to 1200ft/sec.) 2. Medium velocity ( 1200-2500 ft/sec) 3. High velocity ( > 2500 ft/sec)

CLASSIFICATION OF FIREARMS

RANGE OF SHOTGUNUsual range 30 – 40 yardsMuzzle velocity – 800 – 1000 ft./secHome made gun: muzzle velocity = 500

ft./sec

RIFLED FIREARMSThey fire missiles spinning on their long axis.

The inside of the bore is rifled i.e, it is cut

longitudinally with a No. of spiral grooves (usually 4 – 7)

which run parallel to each.

TWO TYPES:1. HIGH VELOCITY RIFLED WEAPONSRifle: It is a long barreled weapon with rifled

bore and is fired from shoulder.

Rifle caliber = 0.30Muzzle velocity = 2500 ft./sec,Spin = 3000 revolutions/secRange = 600 yards.

Rifles may be single shot , semi automatic, automatic.

2. LOW VELOCITY RIFLED WEAPONS:e.g, RevolverA hand gun, not over 10 inches, with a

rotating drum or cylinder behind the barrel. This drum has chambers for loading 5 or more cartridges.

Muzzle Velocity = 600 – 800 ft/sec

PISTOL: It has no cylinder. Cartridge is loaded into the

Chamber directly. It may be single shot, repeating

(having magazine), semi automatic, self-loading.Range: 100 yardsMuzzle Velocity: 1200 ft/sec

AIR PISTOLS + AIR GUNS:They release pellets; which are propelled by air compressed in a cylinder.

Used for killing rats, birds etc.

Range: 30 yardsMuzzle Velocity: 400 – 700 ft. secSome may give fatal injuries to human

beings.

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LONG BARRELLED-RIFLES

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SHOT GUNS

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SHORT BARRELLED-PISTOLS

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Important terms of firearms

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It is any instrument or device that propels a projectile by the expansive force of the gases generated by combustion of an explosive substance.

1.FIREARM WEAPON

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1.BARREL. 2.FIRING PIN. 3.HAMMER. 4.TRIGGER. 5.BUTT. 6.MAGAZINE.

IN GENERAL THE VARIOUS PARTS OF A FIRE ARM ARE:

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It consists of a cylindrical steel tube, which is closed at its proximal end known as BREECH END

DISTLE END which is always open known as MUZZLE END.

Breech end contains a chamber for accommodating cartridge and may carry an extractor to remove the cartridge case after firing.

BARREL:

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A firing pin is present incorporated with hammer and on loading, it is held in cocked position on pulling the trigger it hits the sensitive primer at the base of cartridge and firing occurs.

FIRING PIN:

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In most of the guns a hammer is present which on loading the weapon is held in cocked position and on pressing the trigger, hammer strikes the primer leading to fire (if hammerless than firing pin strikes ).

HAMMER:

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It is a lever situated in front of butt or hand grip.

As the weapon is cocked and trigger is pressed it releases firing pin or hammer resulting in the detonation of the primer in the percussion cap of a cartridge.

TRIGGER:

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Is part of fire arm gripped in hand in small barreled fire arms such as pistols, revolvers etc.

While the butt is long and shaped to fit the shoulder in cases of shot gun and rifles.

BUTT OR GRIP:

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It is a spring loaded box or container carrying a number of cartridges. It may be separated or attached.

MAGAZINE:

Means the diameter of the interior of the barrel of a firearm and is expressed in inches or in millimeters.

Bore / Gauge/Calibre:

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Projectile: Any article being capable of projecting with great force from a fire arm weapon is known as projectile such as pellets in shot guns and bullet in rifled fire arms.

Bullet: means the projectile of a rifled firearm.

Cartridge: means one unit ammunition.

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Technically means the diameter of the inside of the bore(land to land) in 1/100th of an inch.

Thus caliber 22 means 22/100 inch = 0.22inches.

Calibre:

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Means a small metal cap, at the base of the cartridge, holding a sensitive mixture that is detonated by a blow either from a hammer or firing pin.

Primer:

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Means the deviation between the long axis of the bullet and the axis of the path of the bullet.

Yaw:

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Velocity: it means speed of the projectile in feet per second or meters per second.

MUZZLE VELOCITY:The maximum velocity of the projectile when it comes out of the muzzle of firearm is known as muzzle velocity.1. Shot Guns. 1000 feet/ sec.2. Rifles. 2000-3000 feet/Sec.3. Pistols. 1200 feet/Sec.4. Revolvers. 600 feet/Sec.5. Air Rifles, and Air pistols 400-700 feet/Sec.

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Range: It means the distance that the projectile travelled from the muzzle to the target. Generally, range of a firearm denotes the maximum distance upto which it can accurately hit the target.

a. EFFECTIVE RANGE:It is that range in which the firearms can cause maximum damage.b. HITTING RANGEIt is that range up to which the projectile can reach the target, but will cause minimum damage.

FIRE ARM EFFECTIVE RANGE

HITTING RANGE

SHOT GUN 30-40 YDS 100-200 YDS

RIFLES 1000-1500YDS 2000-3000YDS

PISTOLS & REVOLVERS

200 YDS 700-800 YDS

EFFECTIVE RANGE & HITTING RANGE

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The internal lumen of the barrel is smooth in smooth bored fire arms such as shot gun,

while it contains spiral grooves running parallel to each other and are seen in Rifles, Revolvers, Pistols.

Barrel

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The function of grooves is to impart a spin movement to the bullet while passing through the barrel.

Advantages of Rifling: 1. it gives spinning movement to bullet. 2. Prevents from wobbling. (stabilizes the bullet). 3. Increases the power of penetration. 4. Gives greater accuracy and longer

range.

RIFLING

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Choking: It means the degree of constriction at the end of the shot gun bore, provided for keeping the shot spread more compact.

It increases hitting range Decreases the spread of pellets Increases the velocity of shot.

Choking:

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FULL CHOCK:constriction is 1mm

HALF CHOCK: constriction is 0.50mm

QUARTER CHOCKED: constriction is 0.25mm

Choking

Smooth, true cylinder weapon in which there is no constriction in the barrel and the size is same i.e, smooth from breech end to muzzle end.

Unchoked

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In case of 12 bore shot gun, we take 1 lb of lead and make 12 rounded balls of equal weight and each ball fits exactly the internal diameter of the barrel.

So as the bore increases the internal diameter of the barrel decreases.

Note: Size of lead shots has nothing to do with the bore No.

BORE:

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In grooved fire arms if we take transverse section of barrel, there are depressed areas alternating with raised areas known as LANDS.

Caliber indicates land to land width of the barrel.

CALIBER OR GAUGE: