The forces are Unbalanced and Unequal. Some of the forces are drag, lift, side forces, Magnus force, spin damping force, pitch damping force, and Magnus cross force. The most important of these aerodynamic forces is drag. All the others are very small in comparison when the bullet is spin-stabilized.
Just because the forces are unequal, after travelling for some distance bullet it speed decreases and its path curves toward ground and if it goes without hitting anything it will eventually fall down.
