Ballistics Flashcards
Define a round
A modern unit of ammunition
What are the components of a round?
Cartridge case, bullet, propellant, primer
What is the unit for measuring gunpowder and bullet mass?
the Grain
How many grains are in a pound of gunpowder?
7000
If 1kg = 2.2lb, how many grains are in 1kg of gunpowder?
15400 grains
Define caliber
The internal diameter of the firearm barrel, or the diameter of the projectile
What are examples of class characteristics?
- General firearm class
- General dimensions
- Make and model
- Shape of firing pin
What is proofing?
A process by which the unit is stressed around 30% beyond its normal operating pressures
What is the purpose of proofing?
To ensure the firearm can stand the rigors of normal use and is therefore safe for intended use
What is the general firing procedure?
- A live round is loaded through the breech into the chamber, which is then locked and closed
- When the trigger is pulled, a firing pin strikes the primer cup of the round, leading to ignition of the propellant
- Production of gas leads to increased pressure and at the optimum pressure, the bullet starts to accelerate down the barrel
- The firearm is then either manually or automatically cycled to remove the empty cartridge and insert another live round
What are the two main types of air weapons?
Spring and pre-charged pneumatic
What is rifling?
The formation of the spiral grooves that are formed in the barrel wall
Define lands
Raised section of barrel wall
Define landmarks
Sunken areas on the surface of a fired bullet
Define grooves
Sunken areas between lands in the barrel wall
Define groove marks
Raised areas on the surface of a fired bullet
Define twist direction
Rifling can be cut in either left or right hand configuration. If you look down the barrel, the rifling will be either clockwise or anticlockwise
Define twist rate
The number of revolutions per inch of the barrel length
Define described angle
Angle between the longitudinal bullet axis and inscribed rifling marks
Define broach cut
Uses a single point tool to cut one groove at a time, with each groove taking several cuts to reach the desired depth
Define electro-chemical etching
Uses an electrolyte, which is passed through grooves in a tool whilst in contact with the inside of the barrel to etch away the material and form grooves
What is chambering?
The length of the cartridge
What are the two possible outcomes if the wrong size round is used for a firearm?
- The round is too big for the chamber and either will not fit or will jam in battery after firing. This means the cartridge is stuck in the chamber
- The round is too small so will chamber but is loose in battery. The gun could explode as the cartridge will expand to fill the barrel, crack, and cause an explosion
Why are headstamps important?
Shows who made the ammunition. May reveal the caliber and manufacturers information