An experimental procedure adopted for measuring the erosive burning in solid propellants under transonic and supersonic crossflow Mach numbers is explained. Three formulations of ammonium perchlorate/hydroxyl-terminated-polybutadiene propellants of different burning rates (6, 9, and 16 mm/s at 5 MPa) were used for the study. The study presents the erosive burning results for a range of crossflow Mach numbers from 0.8 to 1.7. Additionally, the adopted experimental procedure clearly demonstrates the choking station movement in grain ports of nozzleless motors. As observed under subsonic crossflow conditions, in supersonic conditions the following conditions hold: 1) The erosive burning effect increases with the increase in both pressure and free stream velocity of crossflow. 2) The propellants with lower normal-burning rates experience greater erosive burning than those with higher normal-burning rates. Negative erosive burning under supersonic crossflow velocities is identified at low pressures.