AMITY INSTITUTE OF FORENSIC SCIENCES
GENERAL FORENSIC SCIENCE (FSIC 605)
FIREARMS AND THEIR CONSTRUCTIONS
MAJJI SAI SUDHA RANI
ENROLLMENT NO: A5901118043
I Majji. Sai Sudha Rani (A5901118043), hereby declare that the following assignment “FIREARMS AND THEIR CONSTRUCTION” is my work carried out under the guidance of Dr. Prateek Pandya in AMITY UNIVERSITY, NOIDA and the materials referred are appropriately sited in the references page at the end of the assignment
? INTRODUCTION OF FIREARMS
? TYPES OF FIREARMS
? CONSTRUCTION AND STRUCTURE OF FIREARMS
INTRODUCTION OF FIREARMS
A Firearm is a portable gun that inflicts damage on targets by launching one or more projectiles driven by rapidly expanding high pressure gas produced chemically by exothermic combustion (deflagration) of propellent within an ammunition cartridge. if gas pressurization is achieved through mechanical gas compression rather than through chemical propellent combustion, then the gun is technically an air gun, not firearm.
Modern firearms can be described by the caliber (I.e. their bore diameter, is given in millimeters or inches e.g.7.5mm,.357in.) or in the case of shotguns their gauage(e.g. 12 ga) by the type of action employed (breech, bolt ,lever, pump, muzzle, revolver, automatic, semi automatic etc.) together with the usual means
Assault by firearms there are 173,000 deaths, globally, in 2015.In 1990 there are 1,28,000 deaths in us 2017 there were 15,613 deaths caused by firearms. In us most of the suicides are firearms suicides and 60% deaths are due to firearms.
The first firearms invented in China combining the man-portable fire lance with projectiles. The earliest firearm depicted is a sculpture from a cave in Sichuan. The oldest gun made of bronze was discovered at a site in Acheng District China.
The Europeans, Arabs, Koreans obtained firearms in the 14th century.The Turks, Iranians and Indians got them in the 15th century.
The development of firearms started during the 19th and 20th centuries. Breech-loading became a standard for the reloading. Instead of loading individual rounds, magazines holding multiple munitions were adopted. Polymers and alloys in firearm construction made weaponry progressively lighter and easier to deploy. Ammunition changed over the centuries from simple metallic ball-shaped projectiles to bullets and cartridges.
Velocities of bullets increased with the metals such as copper or copper alloys that covered a lead core that allowed the bullet to glide down the barrel more easily than exposed lead. Such bullets are “full metal jacket” (FMJ). They do not fragment on impact and infact traverse through a target imparting less energy. FMJ bullets impart less tissue damage than other bullets that expand.
TYPES OF FIREARMS
There are five types of small arms:
? Submachine guns
? Machine guns
There are four types of handguns:
1. Single-shot pistols
4. Auto-loading pistols
A single-shot pistol has one firing chamber with the barrel, which is to be loaded manually.
They are a type of single-shot pistols. Derringers are pocket firearms having multiple barrels. The traditional derringer has two barrels.
Revolver is most commonly used in the United States. It contains a revolving cylinder that contains many chambers, each holds one cartridge. The cylinder is rotated mechanically to align chamber with the barrel and firing pin. The first revolver was produced by Samuel Colt in 1835–1836.
The most common of revolver is “swing out”. On pressing the latch, on the left of the frame and pushing the cylinder to the left, exposes the chambers. Every individual chamber is loaded with a cartridge. The cylinder is swung back to the frame, engaging the cylinder latch. The weapon is currently able to be fired. Once discharge of all the cartridges, the cylinder latch is pressed and also the cylinder is swung out.
An ejector rod, at the front of the cylinder, is pressed to the rear, ejecting the fired cases. The cylinder is currently able to be reloaded.
In break-top revolvers, the frame is hinged at the rear specified, on release
of a top catch, the barrel and cylinder swing down, exposing the rear of the
cylinder for loading. The gap action will eject empty cases from the cylinder. This manner of weapon is comparatively uncommon within the United States. However is that the ancient variety of revolver in nice Great Britain.
The solid-frame revolver is that the oldest variety of revolver, chemical analysis back to Colt’s original weapons during this weapon, the cylinder is control in the frame by a central pin, around that it rotates. The rear of this cylinder is never exposed fully by either “swinging out” or “breaking open.”
Each chamber within the cylinder is loaded severally through a loading gate
on the proper facet of the frame. The hammer of the weapon is often force
back to cock, and also the cylinder is then manually turned in order that a chamber is aligned with the loading gate. A cartridge is inserted. The cylinder is then manually turned to consecutive chamber and a second cartridge is inserted. This procedure is sustained till the cylinder is totally crammed. After the weapon is discharged, the cylinder has got to be manually turned once more and aligned with the loading gate, and every cartridge is ejected through the gate using the ejector rod. this kind of construction is most ordinarily encountered in single-action revolvers and also the early model Sabbatum Night Specials.
The latter term, chemical analysis back to the flip of the century, refers to an inexpensive weapon typically of poor construction and doesn’t talk over with concealability.
Revolvers is also either single-action or double-action sorts. In singleaction revolvers, the hammer should be cocked manually every time the weapon is to be laid-off. Cocking the hammer revolves the cylinder, positioning the chamber with the barrel and also the striker. Pressure applied to the trigger then releases the hammer, discharging the weapon. In double-action revolvers a nonstop pressure on the trigger revolves the cylinder, aligns the chamber with the barrel, and cocks then releases the hammer, firing the weapon. Most double-action revolvers is also laid-off in an exceedingly single-action mode. The amount of pressure on a trigger necessary to fireplace a superior double-action revolver. Solid-frame revolver with loading gate swung open. Arrow points to loading port wherever individual cartridges square measure inserted varies from twelve to fifteen pound. If these weapons square measure cocked and laid-off in single-action mode, less pressure (2–4 lb) is critical to fireplace them. The double-action trigger pull for reasonable, poorly created revolvers is typically abundant bigger, while single-action trigger pull could vary from but a pound to the maximum amount because the double-action pull in an exceedingly superior revolver.
Many single-action revolvers have a “half-cock” notch within the cocking hammer that lies between the position of “full cock” and “fired.” the aim of the half cock notch is to catch the hammer if it accidentally slips from the thumb because it is being manually cocked. Several people incorrectly think about the half cock notch a security position and can carry weapons on “half cock.” Dropping a weapon once on *fr1 cock could cause the hammer to disengage, fly forward, and discharge the weapon. Some single-action revolvers can fireplace from the confusedness position if the trigger is force. Ruger single-action revolvers equipped with a security bar don’t have a half cock notch.
The cylinder of a revolver could rotate either dextral (Colt revolvers) or counter clockwise (Smith ; Wesson revolvers). This distinction has resulted in a range of deaths among people taking part in Russian roulette, in which an individual masses one chamber of a revolver and spins the cylinder. They then “peek” to find the cartridge. If it’s in any cylinder except the one that will be turned into firing position on pull the trigger, the gun is then place to the top and also the trigger force. If the cartridge is within the deadly chamber, the player makes some excuse to spin the cylinder once more. this technique of playing Russian roulette is on paper “safe” if one is aware of that approach the cylinder rotates. An individual aware of taking part in the sport employing a Colt revolver may strive it with a Smith & Wesson revolver within which the cylinder rotates in the opposite direction and should expertise a fatal conclusion to the “game.”
Auto-loading pistols (automatics):
Auto-loading or automatic pistols make up the fourth class of handguns. The term “automatic pistol” may be a misnomer, as this manner of shooting iron is Associate in Nursing auto-loader within which the trigger should be force for each shot laid-off. Notwithstanding the right word, however, these weapons square measure invariably known as “automatics” or simply “pistols.” These pistols use the forces generated by the laid-off cartridge to work the mechanism that extracts and ejects the empty cases, masses the recent cartridge, and returns the mechanism into position to fireplace consecutive spherical (Figure one.4). The first commercial shooting iron was made in 1893 by Borchardt; this weapon was the precursor of the Luger.
The cartridges square measure virtually invariably keep in an exceedingly removable magazine in the grip of the shooting iron. Some automatic pistols, like the Intratec policeman nine, and the Mauser M1896, have the magazine before of the trigger guard. The Calico motor vehicle shooting iron uses a fifty or one hundred spherical helical-feed magazine on the highest rear of the frame. The term “clip” is usually used synonymously with the term “magazine.” In fact, a clip may be a device designed to facilitate the loading of a number of cartridges into a magazine, however, the general public use the terms interchangeably.
There square measure 5 ways of operation of automatic pistols: blow-back,
delayed or unintelligent blow-back, blow-forward, recoil, and gas. solely 2 of
these ways square measure presently in widespread use: blow-back and recoil. In a
blow-back action, the pressure of the gas made by combustion of the
powder forces Associate in Nursing unbolted slide to the rear, so beginning the cycle of extraction, ejection, and reloading.
The weapon has simply been laid-off. The slide has begun to recoil
with the bullet a couple of inches before of the muzzle.The slide has recoiled all
the approach back. The laid-off cartridge case is being ejected and also the gun cocked. The slide can currently step forward, chambering a brand new spherical.
Heckler and Robert Koch P7 pistols square measure blow-back-operated pistols with a recoil breaking system that delays rear of tube gap. On firing the gun,
part of the propellant gas is directed through alittle vent within the barrel ahead
of the chamber into a cylinder below the barrel. A piston hooked up to the
slide enters the face of this cylinder. The gas getting into the cylinder acts
against the piston, specified because the slide begins to maneuver rearward by virtue of the recoil pressure, the movement of the piston within the cylinder is resisted by the pressure, delaying the movement of the slide and delaying the
opening of the rear of tube. Another uncommon feature of this weapon is that the
firing pin is cocked by a squeeze cocker incorporated within the front of the grip.
On grasping the grip, the fingers depress the squeeze cocker,
automatically cocking the gun. If the pressure on the grip is discharged, the
squeeze cocker goes forward uncocking the gun. P7 pistols have fluted firing
chambers and two-dimensional figure shaping of the barrels.
In a recoil-operated shooting iron, the barrel and also the slide square measure fast
together at the instant of firing because the bullet leaves the barrel, the rearward
thrust of the propellant gas on the cartridge case starts the barrel and slide
moving to the rear. once a brief distance, the barrel is halted, and also the lockup
device is withdrawn from the slide. The slide then continues to the rear, ejecting the laid-off case and beginning the reloading cycle.
Traditionally, automatic pistols have had a minimum of one operated by hand
safety device. Manual safeties square measure thumb items or buttons that square measure mounted on either the slide or receiver. Usually, on the left facet, they
are currently typically ambidextrous or reversible. Golf stroke on the security locks the firing mechanism (hammer, striker, and typically sear) and prevents the weapon
from discharging. Less normally, automatic pistols, e.g., the Colt M1911, are
equipped with grip safeties, movable items mounted within the grip which stop association between the trigger and also the sear except once the pistol is control firmly within the hand, prepared for shooting. The grip safety is control out by springs once at rest. Grasping the grip pushes the piece in and permits connection between the trigger and sear and so firing of the weapon.
Many of the newer double-action automatic pistols have a thumb piece
on either the slide or frame that outwardly resembles the same old safety lever
but is really a decocking level it’s going to air the left facet, ambidextrous or reversible. once this thumb piece is pushed down, the hammer falls. The weapon won’t discharge, however, because the thumb piece locks the striker and/or rotates a steel surface between the hammer and the striker to forestall contact between the two. In some weapons, the decocking lever currently functions as a security and also the weapon won’t fireplace as long as this device is down. different automatic pistols don’t have any manual safety however solely a decocking lever, e.g., Sig-Sauer.In such guns, depressing the thumb piece causes the hammer to drop, golf stroke the gun on a double action mode however not golf stroke on a security.
The Glock pistols have neither a operated by hand safety nor a decocking lever.
The Sig-Sauers, in addition as most of the newer quality automatics, are equipped with a striker safety (lock). This internal device locks the firing pin in situ preventing forward movement and so accidental discharge. In order to fireplace the weapon, the trigger should be force back so as to disengage this safety.
The slide then comes forward to chamber a brand new round and cock the weapon.
Some pistols have a tool that tells whether or not the chamber contains a cartridge. This could be a protrusive pin at the rear of the slide or simply protrusion of the extractor. Some automatic pistols have magazine safeties. This device prevents discharge of the weapon once the magazine has been removed from it. In some weapons, it’s potential to deactivate or take away this device.With rare exceptions, presently factory-made revolvers don’t have manually operated safety devices.
This truth appears to possess loose British writers, who in their detective and action fiction continually have their characters swing on and starting the “safety” of their revolver. though thumb safeties area unit not gift on trendy revolvers, Smith & Wesson did at only once manufacture a model with an edge safety. As regards derringers, could or may not be equipped with a push-button safety that blocks the autumn of the hammer.
Preparing AN side arm to fireside involves 2 steps. First, the loaded magazine is inserted into the grip. The slide is grasped, force rearward, and released. A spring drives the slide forward, baring a cartridge from the magazine and loading it into the chamber. The weapon is currently cocked and ready to be laid-off. If the weapon contains a operated by hand safety, the safety may currently be applied and therefore the weapon carried during a cocked-and-locked mode.
Alternatively, the weapon is also decocked victimisation the decocking switch or by
holding the hammer back (usually with the thumb), pressing the trigger and gradually lowering the hammer. within the case of weapons of older style (the Colt M1911, the Browning HiPower), to fireside the gun once the hammer is lowered, the hammer should be manually recocked for the primary shot. After the first shot, the operative mechanism of the automated small-arm mechanically cocks the hammer. Most auto-loading pistols area unit currently equipped with a double-action trigger that may cock and hearth the primary shot as a results of continuous pressure on the trigger. In these weapons, once the hammer is lowered, in order to fireside, one simply pulls the trigger. After this, the weapon mechanically cocks itself for every succeeding shot. Even in double-action automatic pistols, however, the slide should be force back at first to chamber a cartridge.
Some of the newer double-action auto-loading pistols area unit factory-made
in a variety of variations. Thus, they will be purchased double action solely
and with or while not safety levers. Browning contains a model, the BDM (Browning
Double Mode), that contains a screw-slotted selector on the left facet of the slide.
Using it, the trigger and hammer may be set for standard double/single action or double action solely.
The Colt Model 2000 (now discontinued) had a slippery trigger; turningbarrel
locking system; chemical compound frame; slide latch; hammerless striker and
automatic internal striker block that’s cleared solely within the last fraction of
trigger movement. It solely fires within the double-action mode.
Beretta manufactures auto-loading pistols with a collapsable barrel for firstround
loading during this weapon, a loaded magazine is placed in the grip. A latch is depressed on the facet of the frame and therefore the barrel tips up exposing the chamber. A cartridge will then be inserted directly into the chamber. The action is then closed and therefore the weapon is currently prepared to fire. A spherical also can be divided the standard method by actuation back and emotional the slide.
Following its introduction into the us, the Glock small-arm became involved in dispute once members of the media and a few politicians contended it absolutely was a “plastic gun” that wasn’t detectible by x-ray or metal detectors. This is, of course, nonsense. whereas the gun will have a chemical compound frame, the slide, barrel, and internal elements area unit steel. Since then, a number of alternative pistols with chemical compound frames are introduced.
A rifle may be a small-arm with a rifled barrel that is intended to be laid-off from the
shoulder. Barrel length is immaterial in classifying a small-arm as a rifle. However,
U.S. Federal law needs rifles to possess a minimum barrel length of sixteen inches. the categories of rifles ordinarily encountered area unit single-shot, leveraction,
bolt-action, pump-action, and auto-loading. A single-shot rifle has one chamber integral with the barrel that must be manually loaded each time the weapon is laid-off. A lever-action rifle contains a lever below the grip which is employed to open the rifle action, to extract the cartridge case, and, in closing the action, to insert a recent cartridge within the chamber and to cock the gun.
In a bolt-action rifle, a handle comes from a bolt. Actuation back and pushing forward on this projection causes the bolt to extract and eject a cartridge case then to insert a replacement cartridge whereas cocking the gun. The slide-action rifle uses the manual movement of a slide below and parallel to the barrel to open the action, extract and eject a cartridge, load a recent cartridge, and cock the weapon.
In auto-loading or semi-automatic rifles, the weapon fires, extracts, ejects, reloads, and cocks with every pull of the trigger victimisation the force of gas pressure or recoil to control the action. once every shot the trigger should be released then force once more to repeat the cycle. Auto-loading rifles area unit commonly however incorrectly known as “automatic rifles.” a totally automatic firearm is one that, on actuation the trigger and firing the weapon, utilizes the force of gas pressure or recoil to eject the laid-off case, load succeeding spherical, fire it, and then eject it. This cycle is perennial till all the ammunition is employed or the trigger is discharged. Automatic weapons area unit usually used solely by military and police organizations. whereas it’s doable to change some semi-automatic rifles to deliver automatic hearth, not like the impression given by the media and some politicians, this is often not a straightforward procedure. In fact, such conversions area unit
uncommon. within the us, deaths thanks to full-automatic weapons (rifles and submachine guns) area unit extraordinarily rare. The author has seen solely
three such deaths within the past thirty years, all of that occurred within the same
incident and concerned amerciable drug dealings and an alleged skilled killer.
Weapons ffired within the full-automatic mode area unit terribly tough to regulate. In
most instances, whereas the primary shot is also not off course, consequent rounds fly high and to the correct.
The term “assault rifle” refers to a rifle that is: (1) auto-loading, (2) has a
large-capacity (20 rounds or more) detachable magazine, (3) is capable of
full-automatic hearth, ANd (4) fires an intermediate rifle cartridge. This term
has been corrupted by the media and a few politicians to incorporate most selfloading weapons. they need additionally coined the meaningless term “assault pistol” which seems to confer with giant, ugly-looking pistols having large-capacity
magazines (20 to forty rounds) or to semi-automatic versions of submachine
guns like the Uzi . “Assault pistols” area unit with rare exception cumbersome, tough to shoot, inaccurate, and cheaply created. They are usually noninheritable by people with very little data of firearms who associate the effectiveness of a weapon with “ugliness.”
Weapons that fireside small-arm ammunition don’t seem to be by definition assault rifles, nor area unit autoloading rifles with mounted magazines that were ne’er supposed for full-automatic hearth. the simplest example of the latter weapon is that the SKS-45 whereas this weapon is an auto-loader and divided for an intermediate-power cartridge, it’s a set ten-round magazine and was never supposed for full-automatic hearth. The weapon is also altered to just accept a 30-round magazine, however.
There is a gaggle of weapons that may be thought-about “assault rifles” if one eliminates the factors of full-automatic capability. this might embody weapons like the AKS-47, MAK-90 and Colt AR-15 Sporter and their variants .These area unit semi-automatic versions of the AK-47 and M-16 assault rifles.
One of the common fallacies concerning assault rifles is that the injuries they
produce area unit a lot of severe than those thanks to normal centerfire rifles. In fact,
the wounds area unit less severe than those made by nearly all looking rifles
even the Winchester M-94 (introduced in 1894) and its cartridge the .30–30
(introduced in 1895). In managing rifles, the severity of the wound is set by the number of K.E. lost by a bullet within the body. The intermediate cartridges utilized in assault rifles possess considerably less K.E. than a daily centerfire rifle cartridge.
Intratec investigator nine typically stated as AN “assault small-arm,” is simply a
cumbersome, ugly-looking small-arm with an outsized magazine capability designed for looking. additionally, since most ammunition utilized in these weapons is loaded with a full-metal jacketed bullet, the wound is even less severe than one may expect.
A firearm may be a weapon that’s supposed to be laid-off from the shoulder; it’s
a sleek bore and is intended to fireside multiple pellets from the barrel. Again,
barrel length is immaterial in classifying a small-arm as a firearm, although
U.S. federal law needs a stripped barrel length of eighteen inches. A shotgun
may be classified as a single-shot, over-and-under, double-barrel, boltaction,
lever-action, pump-action, or auto-loading. The over-and below shotgun has 2 barrels one on top of the opposite, and therefore the double-barrel version has its barrels facet by facet. the 2 barrels in these weapons area unit typically of different choke.
Submachine Guns/Machine Pistols
A machine gun or burp gun may be a weapon that’s designed to be laid-off
from either the shoulder and/or the hip; is capable of full-automatic fire; has
a rifled barrel, and fires small-arm ammunition. It’s typically incorrectly known as a
“machine gun.” Semi-automatic carbines (excluding the M-1 Carbine) area unit a
variation of submachine guns. These area unit either semi-automatic versions of
submachine guns or weapons that have the external look of a submachine gun. The media has dubbed these “assault pistols.” within the case of semiautomatic versions of submachine guns, the interior mechanism is often so altered that they’re primarily a distinct weapon.
A machine gun may be a weapon that’s capable of full-automatic firing which
fires rifle ammunition. it’s usually crew-operated, however some forms is also
fired by single people. Most machine guns have the ammunition fed by
belts, though some use magazines.
Caliber language for rifled Weapons
Rifles, handguns, submachine guns, and machine guns have rifled barrels; that is, spiral grooves are cut the length of the inside or bore of the barrel shaping consists of those grooves and therefore the metal left between the grooves — the lands.
In the US, the caliber of a rifle or pistol is meant to be the diameter of the bore, measured from land to land. This measuring represents the diameter of the barrel before the shaping grooves were cut. In reality, however, caliber is also given in terms of bullet, land, or groove diameter. Caliber specifications victimisation U.S. system area unit neither correct nor consistent, i.e., the .303 Savage fires a zero.308-in.-diameter bullet, while the .303 British cartridge contains a zero.312-in.-diameter bullet. Both .30-06 and the .308 Winchester cartridges area unit loaded with bullets having a diameter of 0.308 in. The “06” in .30-06 refers to the year of adoption of this cartridge.
American cartridges that originally used black powder area unit selected by
caliber, the initial black powder charge, and, in some cases, bullet weight.
Thus, the .45-70-405 cartridge contains a 405-gr. bullet, 0.45 in. in diameter, and
was originally propelled by seventy grains of black powder. The term “grains”
refers to the load of powder, not the quantity of granules of powder. A few
of the Ballistite cartridges that came get into the late-nineteenth century additionally used this methodology of designation. Thus, the .30-30 cartridge has a .308-in.-diameter bullet originally propelled by 30 gr. of Ballistite.
The best example of confusing caliber designation involves .38 Special and .357 Magnum cartridges. Weapons divided for these calibers have barrels with the
same bore and groove diameters. Bullets loaded in every of those cartridges
have identical dimensions. The .357 wine bottle revolver chambers and fires all
.38 Special ammunition, though a weapon divided for a .38 Special cartridge cannot unremarkably chamber and may ne’er use the .357 Magnum cartridge. The .357 wine bottle cartridge case is, in fact, the .38 Special cartridge case long and loaded with extra propellant. Except for the variation in the length of the cartridge cases, all other physical dimensions are the same for each calibers.
The European system of cartridge designation, that uses the metric system, is a lot of thorough and logical than the U.S. system. It clearly and specifically identifies a cartridge by giving the bullet diameter and therefore the case length in millimeters, yet as by designating the sort of cartridge case. Thus, the Russian rimmed-service round becomes the 7.62×54 mm. The 7.62 refers to the diameter of the bullet; fifty four millimeter indicates the length of the cartridge case; and R indicates that the round is red-rimmed.SR are used for semi-rimmed cases, rb for rebated cartridge cases, and B for belted cases. No letter is used for rimless cartridge cases. Thus, the .30–06 within the metric designation is that the seven.62×63 mm.
The term “Magnum”, is used for a cartridge that’s larger and produces higher rate than customary cartridges. within the case of shotgun ammunition, it’s going to or might not be larger however contain more than the standard shell. A Wildcat cartridge is a nonstandard cartridge made by a small Company. It’s not on the market from major ammunition makers.
? Gunshot wounds, practical aspects of firearm. Ballistic and forensic technique by
Vincent J.M DiMaio.