The sabot discard from a gun launched, fin-stabilized projectile is examined from the time of shot ejection until the round enters undisturbed flight. Trajectory perturbations due to muzzle blast, fin shadowing, mechanical contact, and aerodynamic interaction are evaluated and a relative ranking is determined. Analysis shows that muzzle blast and fin shadowing result in negligible changes to the launch angular momentum of the projectile; however, mechanical contact with sabot components markedly alters both the projectile momentum and the subsequent trajectory of the sabot sections. The resultant geometric asymmetry in the pattern of these discarding sections is shown to cause strong aerodynamic interaction between the sabot flowfields and the projectile. For the case investigated, aerodynamic interaction was determined to be the major source of postseparation trajectory perturbation.