Types of firearm
Definitions:
Ballistics
- Forensic ballistics is the science dealing with the investigation of the firearms, ammunition and the problems arising from the use.
Firearm
- 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.
Types of firearm:
Smooth bored weapon (shot gun)-
- Musket
- Shotgun.
Rifled weapon/groove bored firearms
- Rifle
- Revolver
- Pistol
- Automatic pistols, machine guns.
General make up of firearm:
A barrel
- Hollow cylinder closed at the back end called breech end, open at the end called muzzle end
Inside of barrel consists 3 parts
- Chamber at the breech end for the cartridge
- The taper in rifled arm and chamber cone in smooth bore, connects the chamber to the bore
- The bore which lies between the taper and the muzzle
- A bolt or block can be opened to insert a fresh cartridge into the chamber
Smooth bored firearm:
- Bore is perfectly smooth from end to end
- They fire round pellets(Not bullets)
- The hitting range is quite small
Muskets-
- smooth, bored guns used by constables, has a long fore stuck and usually takes a bayonet at the muzzle (military gun)
Barrel-
- steel tube, as long as 40-48 inches and as short as 24-30 inches
- Choking is the constricting device present at the muzzle end of the shotgun
- The function of choking is to decrease the spread of shot.
The spread of pellets from a fully choked barrel is given below:
- 10 meter – 25 cm
- 15 meter – 35 cm
- 20 meter – 45 cm
- 30 meter – 75 cm
Note:
- In a choked-bore the distal 7-10 cm of the barrel is narrow.
- May be single barreled or double barreled.
- Are effective upto 30-30 Yards
Shot gun cartridge:
- Consists of a case of short metal cylinder which is continuous with a card board or a plastic cylinder
- The case is rimmed to keep cartridge in correct position in chamber
- Length of cartridge= 5-7cm
- Cartridge case of shotgun has percussion (detonator) cap at the base of rim and top wad (retaining cardboard) at top.
- Wad is responsible for separation, sealing, optimal pressurization & lubrication but not for fatal injuries
Groove bored/rifled firearms:
- Spiral grooves (2-20, usually 6) inside the barrel to impart spin movement to bullet, to keep the bullet in straight line to target.
- Rifles have firing range of 1000m.
- The killing range of a military rifle is about 300 yards.
- Striking range is small in case of pistol and revolver.
- Rifled firearms are divided into
- Low velocity
- Medium velocity 360-750 m/s
- High velocity >900 m/s
- The caliber or gauze of rifle is measured distance between two diagonally opposite lands.
- Rifle may be single shot, repeating, semi-automatic, automatic.
- Revolvers are so called because the cartridge chambers revolve before each shot to bring the next cartridge opposite the barrel
- Revolver has a cylindrical megazine at the back of barrel and can accommodate 5-6 cartridge each in a separate chamber.
- Effective range is 100 m.muzzle velocity is 150 m/s.
- Air rifle & air pistol release shots or pellets (skirted) which are propelled by compressed air /gas
- Some weapons use cartridges of liquid CO, as the propellant.
Exam Important
- Caliber of a rifled gun is calculated by distance between two diagonally opposite lands
- Cartridge case of shotgun has percussion (detonator) cap at the base of rim and top wad (retaining cardboard) at top.
- Wad is responsible for separation, sealing, optimal pressurization & lubrication but not for fatal injuries
- The killing range of a military rifle is about is 300 yards.
- Choking is the constricting device present at the muzzle end of the shotgun
- Air rifle & air pistol release shots or pellets (skirted) which are propelled by compressed air /gas
- The effective range of shot gun is 30 -40 yards
The spread of pellets from a fully choked barrel is given below:
- 10 meter – 25 cm
- 15 meter – 35 cm
- 20 meter – 45 cm
- 30 meter – 75 cm
- Shotgun does not contain use bullet.
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