Rifling spins the shell so its angular momentum vector resists tipping (gyroscopic rigidity). Aerodynamic torque from crosswind or yaw doesn't tip the shell over — it precesses the spin axis sideways instead, which is exactly how the real "gyroscopic drift" of spin-stabilized projectiles arises, and the same rigidity principle used in mechanical rate-gyro guidance sensors.
L = I·ω_spin (angular momentum)
Ω_precession = τ_disturbance / L
lateral_drift ≈ ∫ v·sin(Ω·t) dt over flight time
- Spin rate — higher spin increases angular momentum L, which resists precession (more gyroscopic stability, less drift).
- Muzzle velocity — scales range and flight time via the ballistic trajectory.
- Launch angle — sets the parabolic arc shape; 45° maximizes range at fixed velocity.
- Disturbance torque — crosswind or aerodynamic yaw torque that drives precession and lateral drift.
The top strip is a bird's-eye (top-down) view of the same shot, showing how the lateral drift pulls the impact point off the straight firing line.