30 Questions
What is the primary purpose of priming compounds in gun ammunition?
To provide the initial ignition of the gunpowder propellant
What is the primary difference between corrosive and non-corrosive priming compounds?
Corrosive primers contain potassium chlorate, which can contribute to corrosion in the gun barrel, while non-corrosive primers do not
Which of the following is not a characteristic of black powder, the traditional European gunpowder?
Contains a higher percentage of sulphur compared to modern smokeless powders
What is the primary difference between erosion and corrosion in gun barrels?
Erosion is caused by the expansive force of the gunpowder, while corrosion is caused by rust formation
What is the primary function of gunpowder, also known as the propellant or power charge, in small arms ammunition?
To generate the expansive force of gas that propels the projectile
Who is credited with the invention of black powder, the earliest form of gunpowder?
Roger Bacon, an English monk and scientist
What is the term used to describe the ability of a bullet to maintain its velocity against air resistance?
Ballistic coefficient
Which of the following best describes the term 'yaw'?
The unstable rotating motion of a bullet
What is the term used to describe the bouncing of a projectile after hitting a surface?
Ricochet
Which of the following is the correct velocity range for a rifle bullet?
2,500 ft/sec
What is the term used to describe the tumbling of a bullet in its flight and hitting the target sideways?
Keyhole shot
Which of the following best describes the term 'drift'?
The curve taken by the bullet while in flight due to rifling
What is the bore diameter of a firearm?
The distance measured between two opposite lands inside the bore
How are lands defined in relation to a firearm's bore?
The elevated portion of the bore
What is the function of rifling direction in a firearm barrel?
To ensure gyroscopic stability in flight by causing rotation
How is pitch of rifling defined in a firearm barrel?
The measure of twisting of the lands and grooves
What determines the width of the lands in a firearm's barrel?
The bore diameter, grooves width, and number
What is meant by 'number of lands and grooves' in firearms?
The count of elevated and depressed portions inside the barrel
What is the main difference between low explosives and high explosives?
Low explosives produce a dull 'boom' and push-type damage, while high explosives detonate with a sharp 'crack' and produce violent shattering damage
What is the main characteristic of a detonation explosion?
It results from the sudden decomposition or combustion of unstable compounds
Which of the following is NOT considered a high explosive?
Black powder
What is the main characteristic of a pressure explosion?
It is caused by the sudden breaking apart, shattering or bursting in pieces due to internal pressure, as that of gas or steam
Which of the following is NOT a characteristic of a bomb?
It is fired by a time fuse
What is the main difference between low and high explosives in terms of their explosion velocities?
High explosives have higher explosion velocities than low explosives
What are groove marks?
Marks found on a fired bullet caused by the grooves of the barrel, matching the number of grooves (lands) in the barrel
What are skid marks in the context of firearms examination?
Marks found on fired bullets from a revolver, typically near the front due to the bullet's initial forward movement
What causes stripping marks on fired bullets?
Worn-out rifling in the barrel due to corrosion or excessive use
What are shaving marks, in the context of firearms examination?
Marks commonly found on bullets fired from a revolver due to a poorly aligned barrel
What are slippage marks?
Marks found on fired bullets passing through an oily or oversized barrel
Which of the following marks is considered one of the most important for firearm identification using fired cartridge cases?
Firing pin mark
Study Notes
Priming Compounds
- Corrosive priming compounds contain potassium chlorate, which produces potassium chloride when ignited, drawing moisture from the air and accelerating rusting and corrosion in gun barrels.
- Non-corrosive priming compounds are mostly used today, consisting of:
- Potassium chlorate (initiator & fuel) - 45%
- Antimony (element & fuel) - 23%
- Fulminate of mercury (initiator) - 32%
Gun Powder
- Also known as propellant or power charge, gun powder is a mixture of chemicals designed to propel a projectile by means of its expansive force of gas when burned.
- Classified as a low-explosive mixture, gun powder burns rapidly upon ignition.
- There are two types of powder in small arms:
- Black powder (Europeans) - oldest propellant powder, consisting of:
- Potassium nitrate - 75%
- Sulphur - 10%
- Charcoal - 15%
- Characteristics:
- Oldest propellant powder
- Consists of irregular grains with a dull or shiny black surface
- Produces grayish smoke and leaves residue in the barrel
- Burns with reasonable rapidity when ignited
- Black powder (Europeans) - oldest propellant powder, consisting of:
Ballistics
- Velocity: the rate of speed of the bullet per unit of time, usually expressed in feet per second (ft/sec)
- Revolver: 600 ft/sec
- Pistol: 1,200 ft/sec
- Rifle: 2,500 ft/sec
- Shotgun: 3,300 ft/sec
- F.Pull of Gravity: the downward reaction of the bullet towards the earth surface due to its weight
- Air Resistance: the force of the air encountered by the bullet in its flight
- Penetration: the entry of the bullet into the target
- Ricochet: the bouncing of a projectile after hitting a surface
Exterior Ballistics
- Ballistic Coefficient: describes the ability of a bullet to maintain its velocity against air resistance
- Drift: the curve taken by the bullet while in flight
- Gyroscopic Action: refers to the stillness of its rotating motion, attaining its highest momentum or stability in flight and penetrating power
- Yaw: the unstable rotating motion of a bullet
- Tumble: rotation of the bullet around the center
- Wobble: the unsteady and uneven spin or rotation of a bullet, usually caused by insufficient twist in the rifle barrel
- Keyhole Shot: the tumbling of the bullet in its flight, hitting the target sideways as a result of not spinning on its axis
Class Characteristics
- Bore Diameter: the diameter of the bore, measured in hundredths or thousandths of an inch
- Number of Lands and Grooves: the number of lands and grooves inside the barrel of a given firearm, always equal
- Width of the Lands: dependent on the bore diameter, grooves, width, and number
- Width of the Grooves: measured as the shortest distance between the two dies or edge of a groove
- Direction of Twist: rifling inside the barrel of the gun is either twisted to the left or to the right, causing the bullet to rotate as it passes through the bore
- Pitch of Rifling: the measure of the twisting of the lands and grooves, referring to the distance advanced by the rifling in order to make a complete turn inside the barrel
Explosives
- Explosion: sudden breaking apart, shattering, or bursting in pieces by internal pressure
- Detonation: resulting from practically instantaneous decomposition or combustion of unstable compounds
- Explosive: any substance that may cause an explosion by its sudden decomposition or combustion
- Low Explosives vs High Explosives: difference in explosion velocities, effects, and characteristics
Marks on Fired Bullets and Shells
- Groove Marks: marks found on a fired bullet caused by the grooves of the barrel, same number as the landmarks
- Skid Marks: marks found on fired bullets from a revolver, located at the anterior portion of the bullet
- Stripping Marks: marks found on bullets fired from a "loose-fit" barrel
- Shaving Marks: marks found on bullets fired from a revolver, caused by its forward movement to the barrel
- Slippage Marks: marks found on fired bullets passing through an oily or oversize barrel
- Marks found on fired shells:
- Firing Pin Mark: mark found at the base portion of the cartridge case, near the center of the primer cup
- Breech Face Mark: mark found at the base portion of the shell, caused by backward movement to the breech face of the block
- Extractor Mark: mark found at the extracting groove of the fired cartridge case, caused by its withdrawal from the chamber
Test your knowledge on bullet velocity, gravity pull, air resistance, penetration, and ricochet. Identify the correct velocities for revolver, pistol, rifle, and shotgun. Understand the impact of gravity and air resistance on bullet trajectory.
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