Erosive effects in Polybutadiene Acyrlonitrile and Hydroxyl Terminated Polybutadiene based composite propellants are investigated using a planar geometry combustor. An adjustable port-to-throat area ratio allows high and low port Mach numbers to be evaluated at multiple pressures. Head, mid, and aft motor pressure instrumentation as well as aft burning rate measurements using an ultrasonic transducer provide the necessary information about the operation of the motor. Erosive burning was studied using the classical Lenoir Robillard model, a modified form of Dickenson's model, the Thompson McClure model, and the Saderholm model. Erosive burning parameter estimates were made by fitting to an inferred burning rate based upon pressure measurements and by matching to pressure reconstructions. The experiment covers chamber conditions ranging from 300 psi to 700 psi and port Mach numbers from 0.1 to 0.7. Data and reconstructions of 8 tests are included and indicate that the Lenoir Robillard model is best suited of the models considered to estimate erosive burning using inferred burning rate alone. In addition, no significant differences were observed in regards to erosive burning for the PBAN and HTPB propellants studied herein.