[en] Differences are investigated in pion source sizes derived using π⁺π⁺ and π^-π^- pairs in the large statistics data set collected with the E866 Forward Spectrometer for central Au+Au collisions at 11.6 A. · GeV/c in AGS Experiment E866. These differences in source radii are interpreted using a simple classical description for the Coulomb and the transverse-momentum (p_T) dependent source radius parameters. An estimated effective net charge responsible for the distortion is considerably smaller than the expected total projectile participant protons, which suggests that the system undergoes a rapid expansion in the longitudinal direction before freezeout. This picture is consistent with the results derived from the π^-/π⁺ singles yield ratios for the same reactions