Forensic Ballistics Questions and Answers

Q: Cardite is used in :

Cordite, written 'Cardite' in the paper, is used in the 0.303 firearm.Cordite is a smokeless propellant of nitroglycerine, nitrocellulose and mineral jelly, extruded into cords. It was adopted by the British army in 1889 for the .303 British rifle cartridge, used in the Lee-Enfield rifle, which was long the standard rifle of the Indian police and army; so cordite propellant is closely associated with .303 ammunition.Shotgun cartridges and revolver and .315 rounds generally use other smokeless powders, in flake or granular form, rather than cordite.

Q: Recoil is not affected by :

Recoil is not affected by the breech face, written 'Breach face' in the paper.Recoil is the rearward movement of a gun on firing, explained by conservation of momentum: the momentum of the gun backwards equals the momentum of everything driven forwards. It therefore depends on the mass and velocity of the ejecta, the projectile and wads, and on the momentum of the outrushing gases, which produce the muzzle blast as they leave the barrel.The breech face is simply the surface of the action that supports the cartridge head. It transmits the recoil to the gun and leaves marks on the cartridge case, but it does not change the size of the recoil.

Q: The sectional density of a bullet of mass 158 g and diameter 0.357 inch is :

The sectional density is about 1239 g/inch\(^{2}\).Sectional density is the mass of a bullet divided by the square of its diameter:\[ SD = \frac{m}{d^{2}} \]\[ \begin{aligned} SD &= \frac{158}{0.357^{2}} \\ &= \frac{158}{0.1274} \\ &\approx 1239\ \text{per inch}^{2} \end{aligned} \]Dividing by the diameter without squaring it gives about 443, close to option A, and multiplying instead of dividing gives about 56, option B. (158 is the classic weight in grains of a .357 Magnum bullet; the paper writes the unit as g, and the key's figure follows the arithmetic as printed.)

Q: The most suitable reagent for chemical etching of aluminum alloy surfaces in cases of restoration of erased number is :

The key's answer is Villella's reagent.When a serial number stamped in a metal has been ground away, the stamping leaves a deformed zone below the surface that an etchant can attack at a different rate from the undisturbed metal, which is how the number is brought back. Forensic course notes name Villella's solution (30 ml glycerin, 20 ml hydrofluoric acid, 10 ml nitric acid) as the best reagent for aluminium alloys such as engine surfaces and vehicle identification plates.Fry's reagent (cupric chloride in hydrochloric acid) is the standard reagent for steel and iron, not aluminium. I could not match Thomas's reagent or William's reagent to a standard etchant. The same notes mention a ferric chloride etch for aluminium, which is not among the options. In metallurgy generally Villella's is described for ferrous alloys, so the forensic convention rather than metallurgy decides this item.

Q: Dum-dum bullets were first manufactured in :

Dum-dum bullets were first made near Kolkata.The name comes from the British arsenal at Dum Dum, near Calcutta (now Kolkata), where in the 1890s Captain Neville Bertie-Clay developed .303 bullets with the jacket open at the tip, exposing the lead core. These bullets expand on impact, producing large wounds and greater stopping power. Such expanding bullets were later prohibited in international warfare by the Hague Declaration of 1899.New Delhi, Mumbai and Chennai have no connection with the name.

Q: A jet of steam is useful for restoration of erased number from which of the following surfaces ?

A jet of steam is used to restore erased numbers on wood.When a number is stamped or burnt into wood, the wood fibres beneath are compressed. If the number is later scraped or sanded off, the compressed fibres remain below the surface. Applying steam or moisture makes the compressed fibres swell more than the surrounding wood, so the outline of the original number rises and can be read and photographed.Erased marks on metals are restored by chemical etching or magnetic methods, and on leather and plastics by other techniques, such as heat or solvent treatment for some polymers.

Q: The sectional density of a bullet of mass 158 g and diameter 0.357 inch is :

The sectional density is about 1239 g/inch2.Sectional density is the mass of a bullet divided by the square of its diameter, a measure of its ability to penetrate:\[ \begin{aligned} SD &= \frac{m}{d^{2}} = \frac{158}{(0.357)^{2}} \\ &= \frac{158}{0.12745} \approx 1239.7\ \text{g/inch}^{2} \end{aligned} \]The value 445 is close to what you get by dividing by the diameter instead of its square (158/0.357 is about 443), and 56 is the product 158 × 0.357. The figures 158 and 0.357 are those of a .357 Magnum bullet, whose weight is normally quoted as 158 grains; the paper writes grams, and the answer follows its units.

Q: Musket are :

Muskets are smooth bore shoulder weapons.The musket was a long-barrelled firearm fired from the shoulder, with no rifling in the bore, so its ball did not spin and was inaccurate beyond about 100 metres. It was the standard infantry weapon from the sixteenth to the mid-nineteenth century.A rifled shoulder weapon is a rifle, a rifled hand weapon is a pistol or revolver, and a smooth bore hand weapon would be an early pistol or flintlock pistol. None is a musket.

21.

Cardite is used in :

A.0.303 firearm
B.0.315 firearm
C.12 Bore shotgun
D.0.45 Revolver

Exam Year(s)

MH SET - 2020, SET Exam - 2020,

Answer: A

Cordite, written 'Cardite' in the paper, is used in the 0.303 firearm.

Cordite is a smokeless propellant of nitroglycerine, nitrocellulose and mineral jelly, extruded into cords. It was adopted by the British army in 1889 for the .303 British rifle cartridge, used in the Lee-Enfield rifle, which was long the standard rifle of the Indian police and army; so cordite propellant is closely associated with .303 ammunition.

Shotgun cartridges and revolver and .315 rounds generally use other smokeless powders, in flake or granular form, rather than cordite.

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22.

Recoil is not affected by :

A.The forward motion of the ejecta (Projectile, wads)
B.Outrushing gases
C.Muzzle blast
D.Breach face

Exam Year(s)

MH SET - 2020, SET Exam - 2020,

Answer: D

Recoil is not affected by the breech face, written 'Breach face' in the paper.

Recoil is the rearward movement of a gun on firing, explained by conservation of momentum: the momentum of the gun backwards equals the momentum of everything driven forwards. It therefore depends on the mass and velocity of the ejecta, the projectile and wads, and on the momentum of the outrushing gases, which produce the muzzle blast as they leave the barrel.

The breech face is simply the surface of the action that supports the cartridge head. It transmits the recoil to the gun and leaves marks on the cartridge case, but it does not change the size of the recoil.

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23.

Assertion : 0.22 inch lead air gun pellet requires a minimum of 500 ft/s velocity to penetrate fresh human skin.

Reason : The mass and diameter of lead air gun pellet is relatively less.

A.Both Assertion and Reason are true
B.Assertion is true but Reason is false
C.Assertion is false but Reason is true
D.Both Assertion and Reason are false

Exam Year(s)

MH SET - 2020, SET Exam - 2020,

Answer: C

The Assertion is false and the Reason is true, so the answer is Assertion is false but Reason is true.

Experimental studies cited in gunshot wound texts found that air gun pellets penetrate human skin at far lower velocities than 500 ft/s: about 331 ft/s for a .177 pellet and about 245 ft/s for a .22 pellet. So the Assertion overstates the threshold.

The Reason is true in the sense the key intends: air gun pellets have relatively little mass and a small diameter compared with firearm bullets, so they carry little energy, and their wounding power depends on reaching even these modest velocities. That is why the option with both true is wrong.

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24.

The sectional density of a bullet of mass 158 g and diameter 0.357 inch is :

A.445 g/inch\(^{2}\)
B.56 g/inch\(^{2}\)
C.1239 g/inch\(^{2}\)
D.935 g/inch\(^{2}\)

Exam Year(s)

MH SET - 2020, SET Exam - 2020,

Answer: C

The sectional density is about 1239 g/inch\(^{2}\).

Sectional density is the mass of a bullet divided by the square of its diameter:

\[ SD = \frac{m}{d^{2}} \]

\[ \begin{aligned} SD &= \frac{158}{0.357^{2}} \\ &= \frac{158}{0.1274} \\ &\approx 1239\ \text{per inch}^{2} \end{aligned} \]

Dividing by the diameter without squaring it gives about 443, close to option A, and multiplying instead of dividing gives about 56, option B. (158 is the classic weight in grains of a .357 Magnum bullet; the paper writes the unit as g, and the key's figure follows the arithmetic as printed.)

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25.

Fired bullet found at a crime scene must be collected by using :

A.Forceps
B.Tweezers
C.Tongs
D.Gloves in hand

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: D

The key's answer is that a fired bullet should be picked up with gloved hands.

The striations on a fired bullet, made by the rifling of the barrel, are the basis of firearm identification by comparison microscopy. Metal forceps, tweezers or tongs can scratch the soft lead or copper jacket and add marks that confuse or destroy the evidence. So the bullet is handled gently with gloved fingers (or with instruments padded with rubber or cloth), then wrapped in soft tissue and packed separately in a labelled container.

Gloves also prevent contamination and the loss of trace evidence such as blood, fibres or tissue adhering to the bullet.

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26.

The most suitable reagent for chemical etching of aluminum alloy surfaces in cases of restoration of erased number is :

A.Fry's reagent
B.Villella's reagent
C.Thomas's reagent
D.William's reagent

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: B

The key's answer is Villella's reagent.

When a serial number stamped in a metal has been ground away, the stamping leaves a deformed zone below the surface that an etchant can attack at a different rate from the undisturbed metal, which is how the number is brought back. Forensic course notes name Villella's solution (30 ml glycerin, 20 ml hydrofluoric acid, 10 ml nitric acid) as the best reagent for aluminium alloys such as engine surfaces and vehicle identification plates.

Fry's reagent (cupric chloride in hydrochloric acid) is the standard reagent for steel and iron, not aluminium. I could not match Thomas's reagent or William's reagent to a standard etchant. The same notes mention a ferric chloride etch for aluminium, which is not among the options. In metallurgy generally Villella's is described for ferrous alloys, so the forensic convention rather than metallurgy decides this item.

Discuss in Forum

27.

Dum-dum bullets were first manufactured in :

A.New Delhi
B.Mumbai
C.Chennai
D.Kolkata

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: D

Dum-dum bullets were first made near Kolkata.

The name comes from the British arsenal at Dum Dum, near Calcutta (now Kolkata), where in the 1890s Captain Neville Bertie-Clay developed .303 bullets with the jacket open at the tip, exposing the lead core. These bullets expand on impact, producing large wounds and greater stopping power. Such expanding bullets were later prohibited in international warfare by the Hague Declaration of 1899.

New Delhi, Mumbai and Chennai have no connection with the name.

Discuss in Forum

28.

A jet of steam is useful for restoration of erased number from which of the following surfaces ?

A.Leather
B.Rubber
C.Polymer
D.Wood

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: D

A jet of steam is used to restore erased numbers on wood.

When a number is stamped or burnt into wood, the wood fibres beneath are compressed. If the number is later scraped or sanded off, the compressed fibres remain below the surface. Applying steam or moisture makes the compressed fibres swell more than the surrounding wood, so the outline of the original number rises and can be read and photographed.

Erased marks on metals are restored by chemical etching or magnetic methods, and on leather and plastics by other techniques, such as heat or solvent treatment for some polymers.

Discuss in Forum

29.

The sectional density of a bullet of mass 158 g and diameter 0.357 inch is :

A.\(445\ \text{g/inch}^{2}\)
B.\(56\ \text{g/inch}^{2}\)
C.\(1239\ \text{g/inch}^{2}\)
D.\(935\ \text{g/inch}^{2}\)

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: C

The sectional density is about 1239 g/inch².

Sectional density is the mass of a bullet divided by the square of its diameter, a measure of its ability to penetrate:

\[ \begin{aligned} SD &= \frac{m}{d^{2}} = \frac{158}{(0.357)^{2}} \\ &= \frac{158}{0.12745} \approx 1239.7\ \text{g/inch}^{2} \end{aligned} \]

The value 445 is close to what you get by dividing by the diameter instead of its square (158/0.357 is about 443), and 56 is the product 158 × 0.357. The figures 158 and 0.357 are those of a .357 Magnum bullet, whose weight is normally quoted as 158 grains; the paper writes grams, and the answer follows its units.

Discuss in Forum

30.

Musket are :

A.Smooth bore shoulder weapon
B.Smooth bore hand weapon
C.Rifled shoulder weapon
D.Rifled hand weapon

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: A

Muskets are smooth bore shoulder weapons.

The musket was a long-barrelled firearm fired from the shoulder, with no rifling in the bore, so its ball did not spin and was inaccurate beyond about 100 metres. It was the standard infantry weapon from the sixteenth to the mid-nineteenth century.

A rifled shoulder weapon is a rifle, a rifled hand weapon is a pistol or revolver, and a smooth bore hand weapon would be an early pistol or flintlock pistol. None is a musket.

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