This note describes active instability control experiments in a high pressure, Jet A-fueled combustor that were performed to improve understanding of the factors limiting control performance. A set of experiments were performed where the desired level of instability amplitude suppression was systematically increased. The controller effectively drove the instability amplitude to the desired levels down to approximately 15% of those without control. Attempts to further drive the oscillations to a lower level resulted in deterioration in performance, manifested by a "peak splitting phenomenon. Experiments were also performed at two conditions where the linear and nonlinear characteristics of the self-excited oscillations were varied. They show that the combustor's nominal dynamics (i.e., without control) has an important impact upon active control system effectiveness.