A firearm is an instrument which discharges a missile by the expansive force of the
gases produced by the combustion of the propellant in a closed space.
Principally a gun consists of three parts :
2.Action (combination of firearm parts that perform loading, feeding, firing, extracting
Classification of Firearm weapons :
Muzzleloader (Musket) : A firearm that is loaded by pushing the projectile into the gun
from the muzzle and down the smooth barrel. Muzzleloaders are almost obsolete
and nowadays all guns are Breechloaders.
The inner surface of the barrel may be :
2.Rifled when it has rifling [ grooves (spiral cuts in the bore) alternating with lands
(raised ridges in the bore that engrave the bullet) run paralleled on the inner surface
of the barrel.]
Rifling is done to impart a rotational spin to the bullet along its longitudinal axis. This
spin stabilizes the bullet in nose-on flight in consistency of trajectory (gyroscopic
Rifling affects the bullet to :
1.Overcome the resistance of air and gravity through the gyroscopic stability
2.Increase in the range
3.Increase in the striking velocity and impact powerful penetration.
4.Help in the identification of the causal weapon.
Rifled Weapons (with rifled barrels) :
1.Handgun : A firearm designed to be fired from the hand and having a short rifled
Revolver (non- automatic), having a revolving cylinder containing several chambers
each of which holds one cartridge and rotates each time the trigger is released. The
spent cartridge case is retained within the cylinder after firing .
Pistol (Semi-automatic), having a removable magazine storing cartridges with a
mechanism for auto-loading . This type of action automatically ejects a spent
cartridge and loads the next one through the gas energy of the previously fired
cartridge. It fires one cartridge with each pull of the trigger .
2. Rifle ( military and hunting weapons): A firearm with a long rifled barrel designed to
be fired from the shoulder .
Non- automatic (bolt, lever and pump actions)
In pump action, the action manually cycles every time a gun is fired, ejecting the spent
Automatic, A firearm design that automatically feeds cartridges, fires, extracts and
ejects cartridge cases as long as the trigger is fully depressed and there are
cartridges in the feed system, thus capable of discharging multiple rounds within
Shotguns = Smooth Bore Weapons
The Shotgun is a firearm with a smooth long barrel designed to usually fire multiple
shots/pellets and to be fired from the shoulder.
Ghaffir gun(Greener, Schneider and Remington), now rarely used
Sporting Gun, single and double barreled.
Choked Sporting Gun, where the diameter of the barrel at the muzzle end less than
the breech end to delay dispersion of shots
Recently, Military Shotgun (bolt, lever and pump actions and Auto-loading).
Firearm Cartridges (Ammunition):
Principally, a cartridge consists of a tube (case) with gun powders (propellant)
inside, missile (bullet or shots/slugs) on its top and percussion cap fixed in its
Cartridge Case is usually composed of brass (70% copper 30% zinc) in many sizes. It
keeps the various components in place.
The cartridge case has rim except in semiautomatic and automatic guns where the
cartridge case are with groove.
Shot shell may be all plastic, all brass, or (most commonly) plastic with a brass. Older
shot shells were made of brass and paper .
Percussion Cap is a small cylinder made of brass and slot in the base of cartridges. It
contains the primer; that composed of:
Powered glass to produce heat on friction .
Highly inflammable substance. An explosive substance (such as fulminate of
mercury, mercuric priming was preferred because it did not rust the gunmetal) that
explodes when struck.
Recently Styphnate priming compounds is a blend of lead styphnate , antimony
sulfide (fuel), and barium nitrate (oxidizer) .
An oxygen-donor substance, such as Potassium chlorate.
Propellant (Gun Powder)
Powder burns to produce large volumes of gases under pressure.
Types of Gun Powder:
Black powder, an old propellant, present in old revolvers, some sporting,Ghaffir
(Schneider and Remington) guns. It’s a mixture of potassium nitrate, sulfur and
charcoal. It is very easy to ignite and horribly inefficient, as only about 50% of its
mass turns into gas. It produces more alkaline residue (corrosive to steel) and a
large amount of smoke when ignited. On ignition 1gm results in 300 ml gas.
Smokeless powder, the successor to black powder. It was developed to be safer and
more potent. It does not produce as much smoke as black powder, while on ignition
results in three time gas volume as black powder and a very few neutral residue. It
composes of nitrocellulose with/without nitroglycerine having scales, rods or
Missile is the part of the cartridge which exits the muzzle.
In rifled guns, bullet usually made of lead and sometimes covered (fully or partially) with a
jacket of copper alloy or other metal harder than lead. The pointed tip is more potent
than the round one because that results in least resistance to the bullet passage in air.
Lead bullets traditionally used for revolvers, while metal-jacketed bullets traditionally
used for semi-automatic pistols and high velocity rifles.
The 'dum-dum' was a British military bullet developed for use in India, in an Indian
State called Dum-Dum. It comprised a jacketed .303 bullet with the jacket nose open
to expose its lead core. The aim was to improve the bullet's effectiveness by
increasing its expansion upon impact resulting in more tissue destruction. The phrase
'dum-dum' was later taken to include any soft-nosed or hollow pointed bullet and
explosive-tipped bullet .
A Frangible bullet or a Glazer bullet is one that is designed to disintegrate into tiny
particles upon impact to minimize their penetration for reasons of range safety, to limit
environmental impact, or to limit the danger behind the intended target.
In less lethal ammunition, projectiles designed to incapacitate but not kill having large
dimensions so that impact occurs without penetration to deliver enough kinetic energy
for "stopping power".
Rubber and Plastic Bullets are recent innovation in firearms used by the police and
security forces for riot control . Injury patterns include lacerations, fractures, and
sometime penetrations especially with shorter firing distances.
In non-rifled guns, shots / pellets or slugs vary in shape size and number. Small
spherical machine-made shots are present in sporting guns while large irregular shots
in Greener and semicubical slugs in Schneider and Remington.
External wad is only found in sporting gun ammunition , about 1mm thick and made
of cardboard to cover the shots and keeps them in place.
Internal wad is found in all shotguns ammunition about one cm thick and made of
felt. Plastic internal wad with shots container is found in recent shotgun shells.
Internal wad separates between the powders and shots/slugs to keep them in
place, and acts as a piston to them .
Sporting Gun Ammunition
Bore (Caliber) of gunshots:
For rifled guns, it is
The inner diameter of the barrel from one land to another land, OR
The diameter of the base of the bullet measured in millimeter or fraction of an
inch e.g. bore of 9 mm equal 0.35 inch
For shotguns, it is
Gauge, number of lead balls of the given bore diameter required to make up one pound
a number written on the shot shell base beside the percussion cap e.g. in sporting gun
12, the diameter of its barrel at the breech side equals that of an imaginary lead ball
weighing 1/12 of an English pound .
Science of the motion of projectiles that is further divided into:
Interior ballistics is the study of projectiles in weapons.
External ballistics is the study of projectiles in the air.
Terminal ballistics is the study of projectile penetration of solids. Wound ballistics
concerned with the motions and effects of the projectile in tissue.
Interior ballistics :
Sequence of events on pulling the trigger:
Pulling the trigger released the firing pin, it is spring-driven against the primer, releasing
its spark through the primer hole and igniting the propelling powder charge. The
burning powder produces gas that builds up the internal pressure, forcing the thin
walls of the brass cartridge case tightly against the chamber walls. These
characteristics constitute the primary obturation that prevents gas from escaping to
the rear. As increasing volumes of gas are produced by combustion of the
progressive burning powder, the increasing pressure is transmitted equally in all
directions. Since the only movable component of the cartridge is the bullet, it is forced
forward at increasing velocity, engaging the rifling cut into the barrel .
External ballistics :
Discharge Of Gunshots
Trajectory is the path of the projectile in air, from the moment it leaves the
gun until it hits a target. Bullets do not typically follow a straight line to the
target . Controlled bullet flight is possible because of its ballistic
coefficient and the spin imparted to it by the rifling (gyroscopic effect).
Bullets of different shapes, weights, and calibers do not behave alike in
passing through the air. Round-nosed bullets are retarded more rapidly in
air and tissues than sharp points and consequently they penetrate less well.
Bullet jacket offers increasing resistance to expansion as well as
Bullets travel in a trajectory that becomes more and more curved as range
increases and velocity drops off.
On firing we get a blast of gases accompanied by flame, smoke, unburnt powder, wads
and shots or bullets, all propelled out of the muzzle at the same time, each of which
has a distinct effect on the target.
Sequence Of Events :
1.Flash of light (Muzzle flash), seen before the sound of explosion is heard .
2.Hot explosive gases come out from the muzzle and travel to a distance of 15 cm and
cause tearing of the entrance.
3.Flame and smoke, Flame causing burning reaches a distance equals to half the
length of barrel. Smoke causing blackening around the inlet, reaches a distance
equal to 1-1.5 the length of the barrel. In long weapons with smokeless powder; it
travels for one meter while in long weapons with black powder it travels for 1.5
meters. In short weapons, it travels for 25 cm.
4.Unburnt powder particles, causing tattooing around the inlet. They travel to a
distance of 2 times the barrel length in long weapons with smokeless powder and a
distance of 3 times the barrel length in long weapons with black powder. In short
weapons, it travels for 50 cm .Tattooing is eccentric if muzzle at angle to skin; may be
blocked by hair or clothing; post mortem is moist grey or yellow.
The mass of shots leaves the weapon initially as a solid mass , which progressively
disperses from the weapon.
1. At 1 meter A central hole 2 cm in diameter.
2. At 2 meters A smaller central hole with dispersion 4 cm in diameter.
3. At 3 meters More smaller central hole with more dispersion 9 cm in
4. At 4 meters No central hole i.e. full dispersion of 16 cm in diameter. The
full dispersion in choked guns occurred at 6 meters.
5. At 10 meters Dispersion area is 60 cm in diameter.
6. At 20 meters The whole body is covered with shots.
7. At 50 meters The shots lose power of penetration.
In cases of shotguns Internal wad penetrates the skin within 3 meters and causing a
circular abrasion at 3 – 10 meters & External wad penetrates the skin within 1 meters
and causing circular abrasion at 1-3 meters.
Bullet causes a hole with no dispersion and the distance of firing is estimated from the
degree of bullet penetration. It is not possible to state from the appearance of the
wound whether the bullet was fired from a revolver, pistol, or rifle.
Powder marks are the effects of 3.Flame and smoke & 4.Unburnt powder particles
at the inlet. The silencer may be used to filter out most of the smoke and powder that
emerges from the barrel.
Medicolegal importance of powder marks:
Diagnosis of fire arm injuries
Differentiation between inlet and exit
Identification of the type of powder used
Estimation of the distance of firing
Determination of the direction of firing e.g. powder marks denote the proximal end of
the tract caused by the bullet passing tangentially along the skin and this will be the
end nearer to the assailant.
Medicolegal importance of wads:
Diagnosis of firearm injury.
Estimation of distance of firing.
Diagnosis of the weapon bore.
Mechanism of wound production:
Muzzle energy is the kinetic energy of a bullet as it is expelled from the muzzle of a
firearm. It is often used as a rough indication of the destructive potential of a given
firearm or load.
In general, as the projectile traverses the body, it causes injury by transferring some
of its available Kinetic energy. Severity of damage is proportional to amount of
kinetic energy and the density of the involved tissue .
KE = ½ M V2 KE = kinetic energy
M = mass and
V = speed
The greater the kinetic energy of a projectile is, the greater the wounding potential.
Kinetic energy increases in proportion to increases in the velocity squared; hence the
great wounding potential of high velocity projectiles.
If a projectile does not exit the body, then all its kinetic energy has been transferred to
the tissues. If the projectile exits the body, then only some of its kinetic energy has
been transferred to the tissues.
Although velocity and mass determine the bullet's kinetic energy, its wounding
potential depends on the transfer of that energy to tissues. This potential is realized
by the rate and degree of bullet deceleration by tissue resistance causing the
projectile to shed energy to surrounding structures. The momentum gained by the
tissue causes them to continue this movement even after the passage of the bullet
creating a temporary wound cavity in the tissue, finally disappears leaving the
permanent wound track.
The location, size, and the shape of the temporary cavity in a body depend on:
1. The amount of kinetic energy lost by the bullet .
2. How rapidly the energy is lost .
3. The elasticity and density of the tissue.
Penetrating and Perforating wounds :
Where tissue resistance is sufficient to cause total dissipation of the projectile's
kinetic energy, the projectile remains within the tissues and the wound is called
In perforating wounds, the bullet passes completely through the object with both inlet
and exit wounds. In a perforating wound, the energy imparted is the difference
between that possessed at entry and that remaining at exit.
Projectiles disrupt tissues by two principal mechanisms:
1.Primary wounding mechanism - mechanical action of the projectile displacing the tissues in
its track. Direct laceration of the tissues as occurs with any penetrating object ("drilling
effect"). This is the main mechanism in low velocity gunshot wounds e.g. from a pistol, and
in such cases the permanent cavity seen at autopsy accurately reflects the tissue damage
produced by the path of the bullet .
2. In high velocity rifle wounds, e.g. hunting rifles, there is an additional effect of temporary
cavity formation produced by the large amount of K.E transferred to the tissue, this cavity
may be up to 30X the diameter of the projectile, has a lifetime of 5 to 10 milli-sec, produces
pressures of 100 - 200 atm and collapses in a pulsatile fashion. The diameter of the
resultant permanent cavity is variable but usually larger than the diameter of the bullet. At
autopsy, the evidence of temporary cavity formation may be a wide zone of haemorrhage
around a small permanent cavity; this is deceptive as the tissue damage is greater than it
appears to be. If the pressure of temporary cavity formation exceeds the elastic limit of the
tissue, then the organ may be disrupted ("bursts") and a large permanent cavity seen at
autopsy reflects the size of the temporary cavity. Organs which are dense ( thus cause
greater loss of projectile KE) and relatively inelastic are most susceptible to this bursting
effect e.g. liver. Organs with low density and high elasticity are relatively protected e.g. lung.
Characters of firearm injuries:
1. Loss of substance especially at entrance wounds.
2. Presence of two wounds inlet and exit or may be one wound .
3. Possible presence of Powder marks (Blacking ,Burning, Tattooing) .
4. Beveling in flat bones (skull, ileum, sternum and scapula).
Gunshot Entrance Wounds:
Gunshot wounds can be divided into four broad categories, depending on the range
from the muzzle to target:
1.Contact Wounds (the muzzle touching the skin) :
There is round or oval central defect with an ‘abrasion collar’ (where the bullet has
abraded the skin surface as it passes through it). In all contact wounds;
soot, powder, carbon monoxide, and vaporized metals are deposited in and along the
wound tract. The muzzle imprint and laceration of the skin from effects of gases are
also found .
With Shotgun, the wound of entrance will be circular in shape with a clean-cut and will
have a diameter approximately equal to that of the bore of the weapon. The
mechanical action of the skin rubbing against the end of the barrel causes abrasion of
the superficial layers.
In the case of a double-barreled weapon, the circular abraded imprint of the non-firing
muzzle may be clearly seen adjacent to the contact wound. The wound margins and
the tissues within the base of the wound are usually blackened by smoke and may
show signs of burning due to the effect of flame and the surrounding tissues are said
to be pinker than normal .
The abrasion ring, and a very clear muzzle
imprint, are seen in this contact range gunshot
This is a contact range gunshot entrance wound
with grey-black discoloration from the burned
An abrasion ring, formed when the force of the gases
entering below the skin surface back against the muzzle
of the gun, is seen here in this contact range gunshot
wound to the right temple.
Histologic examination of the entrance wound
site on the skin demonstrates black gunshot
residue and coagulative necrosis .
Atypical entrance wounds are a feature of contact wounds to the head where the
thick bone under the skin resists the entry of gases, which accumulate beneath the
skin and cause subsidiary lacerations to the wound margins, imparting a star-shaped
lacerated appearance .
This is an contact gunshot entrance wound. Since the
barrel contacts the skin, the gases released by the fired
round go into the subcutaneous tissue and cause the star-
shaped laceration. Note also the grey-black discoloration
from the soot, as well as the faint abrasion ring.
Soot is seen on the hand of a suicide
victim, giving an indication that he was holding
the weapon when it was fired.
With a contact or very close range gunshot
wound, it is possible to have blood spatter as well
as sooting on the hand of the person firing the
2. Close Wounds (20cm non contact range) :
Close Wounds lie in a gray zone between contact and intermediate range wounds .The
muzzle of the weapon is not in contact with the skin. The wound margin is usually
fairly smooth and regular and bordered by a pinkish red abrasion. Very
commonly, there is an ‘abrasion collar’. The effects of flame and smokes
occurs, some blackening and burns, and skin and hair may be burnt, although this is
As the range from the muzzle to the target increases, the size of the zone of powder
soot blackening will increase, whereas the density will decrease.
With Shotgun, the shots are still traveling in a single mass. There is only a single large
wound of entrance with possible burning and blackening and burning of skin with
clubbing of melted hairs can be seen around the wound. Muzzle mark is not found.
3. Intermediate Wounds (20cm upto100cm) :
The occurrence of tattooing is pathognomonic. Tattooing consists of numerous reddish-
brown to orange-red punctuate lesions surrounding the wound of entrance .The
density of tattooing is dependent on the distance and caliber. Burning, blackening
may occur .
With Shotgun, up to 1 m, there is a large central defect and the diminishing of the
smoke soiling but powder tattooing persists. Powder tattooing is less dense than the
tattooing a handgun produces at the same range. Just more than 1m, the spread of
shot will begin causing an irregular rim of the central wound called a ‘rat-hole’
.Then, an area with the effect of dispersed shots and a slight abrasion of external wad
may be occurred .
Rat –hole inlet
Entrance wound with an abrasion of
Powder tattooing is seen in this intermediate
range gunshot wound. The actual entrance site
is somewhat irregular, because the bullet can
tumble in flight.
This is an intermediate range gunshot entrance
wound in which there is powder "tattooing" around
the entrance site.
4.Distant Wounds (out of tattooing range) :
The only marks on the target are those produced by the mechanical action of the bullet
in perforating the skin abraded margin “Abrasion ring” and lubricant and debris on
bullet surface wiped off onto the wound edge, grey contact ring‟ Bullet wipe”.
Determination of distance of firing is difficult. At longer ranges (kilometers with a high-
velocity rifle), the entrance hole will have the same features of a round or oval defect
with an abrasion collar unless the bullet being stumbled.
With Shotgun, the tattooing disappears. As distance increases the central hole gets
smaller and the diameter of dispersion increases in size . At the range of full
dispersion the central hole disappears. At ranges greater, there is an increasing area
of multiple small puncture wounds (giving the skin a peppered appearance). At
20meters, there is uniform peppering of shot, rarely fatal. At 50 meters, there is no
penetration; the shots strike the skin causing multiple bruises all over the body.
Gunshot Exit Wounds:
Most bullets are designed to hit the target without exiting, for this imparts the entire bullet's KE
to the target and does the most damage. However, in many situations an exit wound will be
present. This may be due to the use of a projectile more powerful than necessary, or the
projectile may strike an area (such as an extremity) with minimal tissue.
Exit wounds, whether they are the result of contact, intermediate, or distant firing, all have the
same general characteristics. In general it is;
Bigger than entrance wounds (the deformation and tumbling of the bullet are the reasons
why the exit wound is usually larger and more irregular than the entrance.)
Very irregular .
With edges everted .
Without a collar of contusion or abrasion .
Without burnt nor pink coloured skin around .
Without powder marks .
Without ‟ Bullet wipe”.
In unusual circumstances, exit wounds will have abraded regular margins .These are called
shored exit wounds.
With Shotguns, exit is unusual with shotgun injuries as the shot is usually dispersed in the
tissues. The pellets, however, may penetrate the neck or a limb, and in close-range wounds
to the head the whole cranium may be disrupted.
Displayed here is an entrance at the left and an exit at
the right. This particular bullet struck at an angle to
produce the ovoid entrance. Exit wounds vary
considerably in size and shape because the bullet can be
deformed in its transit through the body.
Here is a slit-like exit wound. Note that there is no
powder or soot visible.
Shored exit wound
Differences between Inlet & Exit :
SIZE SMALL LARGE
EDGES INVERTED EVERTED
REGULARITY MORE REGULAR LESS REGULAR
POWDER MARKS PRESENT ABSENT
BEVELING INTERNAL EXTERNAL
Powder Marks :
The distribution of Powder marks around the entrance site may be either symmetric or
eccentric, depending on the angle of the gun to the target at the time of discharge, the
nature of the target (flat or angled), and any covering of the skin, e.g., hair or clothing
which may prevent powder grains from reaching the skin.
GASES 15 CM 1X
BURNING , BLACKENING 25-100 CM 2-8X
TATOOING 50-200 CM 4-16X