Huhtala (1997) discussed the strength and weakness of some existing models for hydraulic piston machines and unfortunately concluded that any model is not accurate enough for wide operating ranges. As an effort to develop an accurate model applicable for wide operating range, Jeong (2006) proposed a performance coefficient model for a hydraulic axial piston motor of swash plate design, which is given by the physical dimensions. In this paper, validity of the new performance model is addressed through experimental analysis. Estimation process for model parameters is established and then performance decision parameters are estimated from efficiency measurement data for a test motor. As the result, maximum and average efficiency estimation error over wide operating ranges of speed $300{sim}2700$ RPM and pressure $20{sim}300$ bar are just 2.33% and within 0.30%, respectively. Hence, it can be said that this paper opens a door toward developing true performance estimation model.