3429000215900001556385-854075General Forensic Science
General Forensic Science
-742950541781900451485045415200039243005179695General forensic science assignment
Firearms and there construction
M.Sc. (forensic science)-I semester
Enrolment no.- A5901118040
AMITY University, Noida (u.p)
400000General forensic science assignment
Firearms and there construction
M.Sc. (forensic science)-I semester
Enrolment no.- A5901118040
AMITY University, Noida (u.p)
I, Chintan Singh (Enrolment no.: A5901118040), hereby declare that the following assignment, “Firearms and constructions” Is my work carried out under the guidance of Dr. Prateek pandya in Amity university, Noida and the material refers are appropriately cited in the references page at the end of this assignment.
TABLE OF CONTENTS
1. Introduction Of firearms
2. Characteristics of firearms
3. Different types of firearms
3.1 Guns including rifles
3.2 Smooth bores
3.3 Rifled arms
3.4.1 Types of shotguns
3.6 .12Bore guns
3.8 Single shot pistols
3.10 Extraction and ejection
4.1 Introduction and concept of ballistics
4.2 Catridges and Projectiles
4.4 Shotgun and rifles cases
4.5 Revolver and pistol cases
4.6 Analysis of projectiles
Introduction of Firearms
Definition- A arms weapon from which a shot is discharged in a projectile motion by gunpowder. It can a rifle, pistol, shotgun, airgun, or any portable gun. The popular conception of fire arms is arm or weapons which are discharged by fire exploding gun powder. Broadly they are come under any of following categories- like shotguns, single-barrelled and double barrelled shot pistols, rifles, single shot pistol, sub-machine gun, revolvers etc.
General characteristics of different types of firearms
If the barrel is long and the butt end of the stock transverse it, so weapon can be placed against the shoulder, it is called a gun or a rifle. If barrel is short and the stock curved down so it’ll be held in hand, it is a pistol or revolver. If the weapon can be loaded from the muzzle only, it is a muzzle loader.
If weapon has more than one short barrels loaded individually, it is a old-fashioned pistol; if, it has only one barrel and a round cylinder permitting severals shots to be fired in succession, it is a revolver. In shotguns the difference in barrel is immureble.
The barrel, is a metal tube in which the charge is placed for firing and in which it’s explode. During combustion, this tube compresses the gases which developed and givesthe missile proper direction.
The stock is the part by which firearm is held and it support the barrel. It also fixed the lockplate and other accessories. Basically made up of wood.
Lock contain the lock and mechanism of trigger (apparatus for the discharge of the weapon.
Acccessories,are the other all parts of the weapon beside the three just named.
They are basically of four types-
3476625183515003.6.1 Revolvers: – Revolvers belong to that class of rifled arm which is intended to be used with one hand only. Revolver is a form of repeating pistol.
Its name derives from the cylindrical magazine which rotates
Immediately in rear of the barrel. This “cylinder “usually holds
5 or 6 cartridges, each in a separate chamber, and each
Chamber can be aligned in turn with the bore. After firing a shot the hammer is cooked, and this cocking of the hammer rotates the cylinder until the next cartridge is in the proper position for fixing. When this one has been fired the operation is repeated. The shooter is thus able to fire five or six shots with great rapidity and without re-loading.
From the view point of construction revolvers can be divided into four categories:
l. Revolvers with barrel firmly fixed to the frame and a revolving cylinder which may be swung out to the side for the purpose of loading.
2. Revolvers with barrel hinged to the frame and carrying a revolvable cylinder which may be broken open to load by releasing the barrel-latch.
3. Revolvers with barrel firmly fixed to the frame and a revolving cylinder which may be removed by taking out the cylinder pin on which it rotates.
4. Revolvers with barrel firmly fixed to the frame and a revolving cylinder operated by the gas pressure.
1809750-317500From the viewpoint of identification the revolver should be classified first by calibre and secondly by percussion. We then have the three primary group:-
1. Revolvers with centre fire, where the percussion cap is placed in the centre of the cartridge.
2. Revolvers with rim fire, where the percussion composition is placed around the inside of the rim of the shell.
3. Revolvers, with pin fire, where the hammer strikes a needle which is placed at the rim of the shell and presses on a percussions cap in cartridge’s interior.
Revolvers with rim fire are not In much evidence nowadays, Although the rim fire .22 calibre
Is used mostly.
9525472440003.6.2 Single shot pistols are also sometimes made as shot Weapon such as .22 pistols. The Derringer is really a single shot pistol of a large calibre, usually have .41 and .44.They hold a single round of ammunition and have to be reloaded after Each and every single shot. They are less complex as compared to automatics pistols and are much easy to operate. Ex- Thompson Center contender.
3.6. Derringers:-They are the small pocket firearms which have multiple barrels, which are individually loaded and fire separately.
3.6.4 Automatic Pistols:- They are the automatic firearms in which trigger must be pulled for every shot fired. These pistols use the force which is generated by fired cartridge, after every shot mechanism is to returned to the position to fire the next round. There are 5 methods for operation of automatic pistols- These are blow back, delayed or retarded blow back, blow forward, recoil, and gas.
3.2 Rifled arms: – In almost all the rifles the bore is cut longitudinally with grooves, such that these grooves are parallel to one another but are cut witch a twist from breech to muzzle.
3.9 Rifles:- .-Most rifles have a single barrel. All modern military rifles have a single steel barrel and a magazine, which is a receptacle that fits below the breech and contains extra cartridges which can be forced into the breach after each empty shell has been extracted. Many sporting rifles are also of this time, but sometimes they ate double-barrelled with no magazine. Such rifles may be either hammer or hammerless in the same way as shot-guns. The constituent parts of a rifle, lock, stock, barrel, etc., are essentially the same as for a shot-gun. The fundamental difference is the rifling of the barrel.
257175035306000The barrel is manually thicker than for a shot-gun, the pressure which it has to stand being much greater. The hollow portions of the titling are the “grooves”, the projecting portions between the grooves are the “lands”, the spiral or twist of the rifting is the pitch as in a screw. The number of the grooves varies and the pitch may run clock-wise as in an ordinary corkscrew, or counter-clockwise.
3.10 Assault rifles:- These rifles are that which are auto loading and has a large capacity detachable magazine. They are capable of full automatic fire. For example AK-47 and AK-74
326707532131000There are semiautomatic versions also present of the AK-47 and M-16 assault rifles. The wound they produce are more severe than that of ordinary centerfire rifles. The intermediate cartridges used in assault rifles have less kinetic energy than a regular centrefire rifle cartridge designed for hunting, as the severity of wound is identify by the kinetic energy lost by a bullet in the body. Most
3.1 Smooth bores:- These are those firearms in which the bore, or inside barrel, is smooth from end to end. The cross section area present in it gives a perfect circle for the bore.
3.3 Shotguns and its types :-
Shotguns are the firearm intended to fired from shoulders and have a smooth bore and designed for striking multiple pellets from barrel.
In most of the cases the double barrel shotguns used. The two barrels being placed side by side or sometimes placed one over another, when it is called an “over and Under” gun.
They are classified on the basis of type of bore, the nature and number of barrels. Double barrels shotguns are made with hammers or hammerless action in which hammer is enclosed inside the body of the action. Single barrels shotguns are cheaper than double barrelled and are made with external hammers. The cheapest single barrelled shotgun is made with bolt action similar to that employed is military rifles.
Double barrel shotguns come in two configurations: the side by side and the over/under shotguns. Original double barrel shotguns are of side by side
3629025381000 Configuration. Early cartridge shotguns also use
side by side configuration. When hammerless
Designs are in trends than over/under shotguns
Got introduced. They provide access to more
Than one choke at a time. Their disadvantage is
that the barrels of the shotguns of both the confi-
gurations are not parallel but slightly angled, so
that the shots converge (40 yards out). Side by side
shotguns are more costly and require practice to
aim effectively than a over/under shotguns.
3.5 .12 Bore gun :- By far the commonest sporting gun is the .1 bore, the diameter of barrel of this gun, is nearly three-quarters of an inch. In describing the bore of shot-guns in 2133600-12827000England, the size of the barrel varies in inverse ratio to the figure given to the bore. The 4 bore is a very heavy wild-fowling gun which can only be fired from the shoulder by a man prepared to take great care and withstand considerable shock.
An 8 bore is also a heavy wild-fowling gun. The .12 bore is the common sporting gun.
The 16 bore is slightly lighter and often used by boys and ladies. The 20 bore is the smallest commonly in use for Sporting purpose Although when properly loaded it will kill game as far off as the 12 ore, naturally much greater accuracy is required in the shooter. The so-called .410 is the next common smaller size. Barrels of modem shot guns are always made of steel.
3.4 Machine Guns
-29527527432000 Machine guns are full automatic firearms that fires rifle ammunition. Its ammunition fed by belts, some uses magazines. It is generally crew operated.
Submachine guns:- It fires pistol ammunition, to be fired from shoulders and is capable of full-automatic fire. These are either semiautomatic version of submachine guns or weapons that have external appearance of machine gun. In semiautomatic version the internal mechanism is very much altered that they are essentially different weapon.
It consist of a small arms cartridge contain cartridge case, a primer, a propellant and a bullet.
3038475167640000CARTIDGE CASES: – made up of brass (70% copper + 30% zinc), less commonly steel. Steel cartridge has polymer coating, its main function is to expand and seal the chamber block escape of gases when cartridge fired. When this Is fired the gas pressure produced by the burning of propellant expand the case tightly against the chambers. There are 3 general shapes for cartridge cases- straight, bottleneck, tapered. Pistols uses straight and rifles uses bottleneck cartridge because it allow more powder to be packed in less space.Cartidge cases are classified into 5 types-
Rimmed cartridge- they contain extractor flange which is larger than the diameter of the cartridge case body.
Semi rimmed cartridge- they also have same extractor flange but they also have a groove around the case body in front of the flange. In metric system of calibre these cartridge is SR.
Rimless cartridge- same as that of semi rimmed cartridge but in metric system of calibre no letter is used for these types of cartidges.
Rebated cartridge- they have an extractor flange that is smaller than the diameter of the case. A groove around the body of case is also present. The metric designation used is RB.
Belted cartridge- raised belt encircling the cartridge case body in front of the groove in the body.
347662525781000Primers :- it is located in the center of the base of the cartridge case. These are of two types for metallic cartidges: Boxer and Berdan American manufactured centerfire rifle and pistol cartridge have boxer primer (consist of brass or gliding metal cup).For rifles and pistols primers are different in construction in that the cups of pistol primers are made with thinner metal. The primer in case of rifle has a mixtue that is more flammable and sustained.
-61912529527500Bullets :- It is the part of the cartridge that leaves muzzle of the firearm on discharging. They were originally lead spheres. They worked remarkably with smooth bore weapons, in which long range and accuracy is not required. Some rifleman’s developed a more rapid way of loading their firearms by used the bullet slightly under bore diameter. This bullet is packed in in a greased patch of fabric,and the spherical bullet and patched were rammed down the barrel together. This speeded up the rate of loading to some extent. Until 1960 bulletss divided into three categories: lead bullets for revolvers, FMJ bullets for automatic pistols and military rifles and semijacketed bullet for hunting rifles. Both FMJ and semijacketd have lead bore.
In lead bullets antimony or tin been used to increase the hardness of alloy. They are lubricated with grease to prevent lead fouling of the barrel. They have one or more cannelures, or grooves. Some of them are coated with vey thin coating of copper or copper alloy. This made bullet both hardness and lubricant and is termed as “Gliding”.
Jacketed bullets are either FMJ or partial metal jacketed. They had a lead or steel core covered by an outside jacket of gliding metal. Cannelures may be present in the jacket of these bullets. Military ammunition like rifle and pistol is loaded with FMJ bullets. They prevent leading of the action and barrel as well as jams that result in large number of leads bullets were fired.
-438150459740003.11 Extraction and ejection: – Before the weapon is reloaded for firing a second shot it is necessary that the previous empty cartridge case must be removed from the chamber. In most of the firearms, manufactured these days there is a device which automatically ejects empty cartridge case when the breach after firing is opened but in other the empty cartridge case is only partially dislodged from exposition in the chamber and it is extracted by hand. This is the difference between ejection and extraction. In both the cases there are imprinting’s on the tired case which are very important from the point of identification of the firearm. It is thus very necessary to understand the principles involved in both the cases.
Ejection of the fired case is brought about by a special lock mechanism which only comes into action when the hammer falls. This lock actuates the extractor and flicks it backwards at the moment when the arm is opened, and so ejects the tired case. A similar extractor is used in all rifles with “falling block” or Mortini actions, but in their case the extractor is actuated by the lever which opens the breech, and ejection is brought about either by the force with which this lever is jerked down, or else by a spring which is only heed from compression by the fall of the hammer.
Gunshot wounds, practical aspects of firearm. Ballistic, and forensic technique, by Vincent J.M DiMaio