AT SGT Ballistics Flashcards
What is the definition of Internal ballistics?
The study of operating processes from when the propellant is ignited until the weapon leaves the barrel
What is the all burnt point?
The point where all propellant has been consumed
What is shot start?
The point where the projectile begins to move
What is muzzle pressure?
Peak over pressure at the muzzle upon breakage of the projectile bore seal
What is muzzle velocity?
Projectile speed at exit from the barrel
What are the 4 phases of internal ballistics?
Charge ignition
Combustion prior to projectile motion
Combustion up to the all burnt point
Gas flow and projectile motion after all burnt point to muzzle exit
What are the goals/objectives of internal ballistics?
Launch the projectile safely
Consistent performance between shots
Achieving the highest possible muzzle velocity
Explain the volume and temperature relationship on pressure
Increase volume causes less pressure
Increase temperature more pressure
What is Pioberts law?
When burning the surface of propellants recede layer by layer in the direction normal to the surface
How are the 6 energies distributed when a projectile is fired?
Projectile (translation and rotation) 32%
Residual heat of gas 42%
Heat lost to gun 20%
Recoil of gun 0.2%
Engraving the driving band / barrel friction 2.8%
Unburnt charge and gas 3%
What can cause the variations in the effects of ballistics? (7)
Charge weight
Propellant size
Chamber capacity
Ignition temperature
Shot start pressure
Bore area
Multiple variations in combination
What is the effect of an increase in charge weight?
Pressure increase
All burnt point moves closer to ignition
Muzzle velocity increase
Regularity in fall of shot improves
What is intermediate ballistics?
The study of the transition from internal to external ballistics that occur in the vicinity of the muzzle
What are 5 types of muzzle flash?
Pre-flash
Primary flash
Muzzle glow
Immediate flash
Secondary flash
Name 3 types of flash reductiontion methods?
Muzzle devices
Type of propellant
Propellant additives
Name 3 types of suppressors?
Conical
Slotted
Bar type
What are the objectives of intermediate ballistics?
Launch the projectiles safely
Launch the projectiles with uniformity
Achieve the highest possible muzzle velocity
What is muzzle energy?
The majority of energy is carried by the propellant gases in the form of heat, pressure and motion.
Why do we use muzzle devices?
Reduce recoil
Suppress flash
Reduce report
How do most flash suppression devices reduce flash?
Break up the barrel shock and mach disc
What is a blast shock wave?
The abrupt increase of pressure from the sudden release of high pressure gas from the muzzle
What are the 2 muzzle gas flow blast fields during firing?
Precursor
Main
What are the 2 main sources of muzzle blast?
Blast shock wave
Flash blast
What is muzzle flash?
The light emitted in the vicinity of the muzzle by hot propellant gases and chemical reactions with the gases and the air.
How is the precursor blast field made up?
Blast shock
Bottle shock - barrel shock and mach disc
The 4 burning characteristics of propellant compositions are?
Burning rate - rate granules reduce when burning
Pressure index - Coefficient burn rate at different pressures
Force constant - pressure generated in a volume
Co-volume - The volume occupied by 1kg of propellant
What are the 2 parts of the blast shock?
Blast shock wave - caused by high pressure propellant gases
Flash blast - rapid temperature rise causing secondary flash causing gas pressure rise
What can reduce blast shock?
Suppressors can reduce blast
Blast absorption
Blast dissipation
Blast containment and control release
What is another name for fume extractor?
Bore evacuator
What is recoil?
The rearward motion of the gun in reaction to the forward motion imparted by the projectile and propellant gases.
2 most common means of stabilisation are?
Spin
Fin
What is trajectory?
The path taken by the center of gravity of the projectile
What are the 4 drag forces?
Skin friction
Pressure drag
Forebody drag
Excrescence drag
What is excrescence drag?
Caused by articles protruding from the shell
What is ballistic coefficient?
Measure of a projectiles ability to overcome drag
What are the forces acting on the projectiles?
What are the 2 gyroscopic forces?
Precession - circular yaw
Nutation - rosette pattern from the rotational forces on the projectile
What 2 parts impart drift onto the projectile?
Spun projectiles due to equilibrium yaw
Rotation of the earth
