Coaxial atomizing sprays are used in industries from gas turbines to food processing. Spray dynamics depend heavily on the primary breakup (near-field) region. The near-field region is challenging to study because it contains thick liquid that is impenetrable to visible light. However, X-ray radiographs are capable of penetrating the dense liquid region, providing insight that is unavailable from visible light testing methods. This study modifies a method used in previous studies for determining the mass-averaged axial velocity from a narrow-angle, injection spray, into a method for studying the mass-averaged axial velocity from a wide-angle, constant spray. Experiments at the Advanced Photon Source at Argonne National Laboratory provided focused-beam X-ray radiographs along the spray. Results showed that the mass-averaged axial velocity along a coaxial spray increased linearly with axial distance from the nozzle for varying momentum ratios. The slope of the velocity-distance relation also increased linearly when plotted as a function of gas Reynolds number. Spray velocity is often considered for individual droplets or for the centerline, but not as a mass-averaged property. However, these results show that the mass-averaged axial velocity has predictable behavior in the near-field region for the conditions that were tested in this study.