Abstract:In the optimal design of a modern gun barrel, there are some aspects to be considered. One of the main factor is internal ballistic which consist of pressure-time, pressure-distance, velocity-time and distance-time curves. In this paper, a simple analytical solution for the plastic stress of an internally pressurized open-ended thick-walled cylinder made of hardening steel which is the closest model to gun barrel is obtained in perfectly plastic and plane stress condition by using energy method and the yield criterion of Von Mises and adding rifle grooves and choosing stress components as basic unknowns and ballistic pressure equation as known. Then results of analytical solution are compared to a numerical model and verified a very well and reliable accuracy. So the resultant can be used easily in calculation of radial expansion velocity and compressive pressure.