There is a PVC projectile in a breech of a fire extinguisher, after shooting this projectile, which the diameter of the ending part is larger than the bore diameter in order to increase the pressure produced inside the combustion chamber, it is gone under a plastic deformation in order to push the projectile inside the bore because of the special design of the projectile, the question is how can I relate the pressure into the elastoplastic deformation of the projectile during the firing process?

I appreciate if you suggest any reliable softwares for simulation of this delicate physical deformation due to the pressure. The main objective is to find the pressure inside the combustion chamber, as it is not possible to easily find the detonation pressure of mixture of versatile kinds of propellants.

Thanks a lot for your answer