External ballistics

Question 1

Path of the projectile

Answer 1

Gravity
Angle of launch
Velocity
Air density, temperature and humidity
Projectile shape
Projectile stability

Question 2

Ideal flight path

Answer 2

A perfect ballistic flight path would not have air resistance
This would be expected in a vacuum
trajectory is even either side of the maximum height

Question 3

Real flight path

Answer 3

Air resistance is taken into consideration
The second half is truncated
Trajectory is uneven either side of the maximum height

Question 4

Aerodynamic forces

Answer 4

Aerodynamic forces and gravity are the most important factors in calculating the true dynamics of a projectile
Aerodynamic drag is typically proportional to the square of the velocity so drag builds significantly with velocity.

Other properties contributing to drag:
The profile or shape of the projectile
The cross-sectional area of the projectile in the direction of travel
Air density

Question 5

Centre of mass

Answer 5

The centre of mass is the point where the bullet balances its weight
The centre of mass is the only point of the bullet that follows the trajectory

Question 6

Centre of pressure

Answer 6

Is the point where the aerodynamic forces act after adding up all of them
In case of the bullet, it is the sum of the drag forces from the air flow.

Question 7

Important concept

Answer 7

The CoP should be rewarded of the CoM but very close to it
- Fin stabilisation facilitates this by creating additional aerodynamic forces at the back of the projectile

Normal spitzer bullet shapes have the CoP significantly forward of CoM
- This makes the bullet want to tumble as this creates a major turning point
- This is why bullets need gyroscopic stabilisation to overcome the want to tumble and keep the bullet point directed towards the impact point

Question 8

Drag Stabilisation

Answer 8

This is achieved by adding fins to the projectile, which creates additional drag forces at the rear of the projectile
This brings the CoP rearward of the CoM, leading to a smaller and less influential turning moment
This results in a stable flight path without the need for any gyroscopic stabilisation
Gyroscopic stability would not be possible with this design anyway as the fins would not fit in this barrel