The problem of internal ballistics is considered, including basic pyrodynamic equation, law charge combustion, gasification law and equations of the projectile motion. A numerical method is used to solve a system of three algebraic and three ordinary differential equations. The software was developed and a number of computational experiments were made to analyze the influence of the charging parameter on the processes occurring during the projectile movement in the barrel channel. The problem of gunpowder burning and a finite-difference method to solve it are considered. The results of this work can be applied to the design of new types of trunks and charges.