A mathematical model is developed -using MATLAB Simulink software package -to simulate, predict, and evaluate the performance of gun recoil system. The used gun is a tank gun with a concentric recoil mechanism. The results are presented in this paper can provide a clear understanding of design parameters affecting the behavior of recoil mechanism and/or improving the performance of recoil mechanisms in the future.A complete study of the constructional parameters that affect the performance of the concentric recoil system is carried out. Then, a mathematical model that includes all governing equations of recoil cycle is developed. Finally, the model is tested for a case study and the results is recorded and compared with others resulting from actual firing test. This paper starts with studying the construction of concentric recoil mechanism for tank gun and analysis of the different forces and resistances influencing the recoiling parts during recoil cycle; then, introducing the equation of motion of recoiling parts during recoil cycle and finally, constructing the simulation program to obtain results.Comparison of simulation results and others obtained from actual firing shows a good match that creates some confidence in the mathematical model. This confidence encourages reliance on this model in evaluation, development, and design of such systems.

Knowing the hydraulic resistance of gun recoil brake is a major task to determine the gun recoil parameters during recoil. Generally, using one-dimensional analytical models simplify determination of the hydraulic resistance coefficient consequently the hydraulic resistance can be easily obtained. However, these models don't give information about the flow inside the recoil brake. For more explanations of the internal flow inside the recoil system, the two-dimensional flow simulation is carried out using CFD solver. Dynamic mesh technique is used with the CFD solver. A user defined function (UDF) is developed to feed the solver by the recoil velocity with time.