Rotating Band - engages the rifling and seals the volume behind the projectile to contain the propellant gasses. The rotating band also centers the projectile like the bourrelet. Base - provides a flat surface for the expanding gasses to push on and accelerate the projectile down the barrel. The base may also contain a firing mechanism to ingite the propellant if self-contained. Next we have aerodynamic forces which provide lift and drag the body as it flies through the air.
Aerodynamic forces are generally proportional to the velocity squared.
Skin drag- friction on the outer surface as it moves through the air 2. Wave drag - a loss of energy that is put into acoustic waves as the body passes through the air. Particularly strong near the speed of sound in air. All drag forces act at the center of pressure and are in the opposite direction as the motion of the projectile. The lift force acts perpendicular to the direction of motion relative to the air stream.