Performing experimental tests on a subscale model is essential for acquiring foundational insights and comprehending the implications of combustion efficiency within practical propulsion technologies. The present study seeks to maximize the benefits of optimization and stop/restart capabilities of a hybrid rocket motor. Utilizing NASA CEA software, valuable approximate results that are instrumental in calculating combustion efficiency was completed as a theoretical study and greatly contributed in building a solid foundation for the experimental phase. Actual fire trials are used in experimental testing, and data is carefully gathered and examined to comprehend the complex details of combustion efficiency. The word "regression rate" is emphasized in particular in the article as a critical performance metric, and its relationship to the propellant grain geometry is examined. The present work dives into the influence of regression rate on combustion efficiency. The objective is to study how the regression rate affects combustion and the development of hybrid rocket engines in understanding combustion efficiency in subscale hybrid rocket motors is made easier by the results of both theoretical and experimental methods. This research offers a useful insight on how to maximize regression rate and thereby increasing combustion efficiency, which could have ramifications for the development of rocket engine technology.