Artillery weapons in general and the artillery types on the tank in particular, after long-term use, some parts on the cannon will be worn out due to friction, and impact, especially the details that need high precision such as the throttling ring and the throttling rod. In this paper, a mathematical model is established to evaluate the influence of the change in diameter of the throttling ring on the reliability of artillery when firing. Numerical calculation applied to the 100mm artillery on the T55 tank. The calculation results show that: The law of recoil braking force is changed when the diameter of the throttling ring dR is greater than 38.5mm, then the maximum pressure in the cavity 1 decreases suddenly by 16.6%. This is undesirable to maintain the stability of the cannon on the tank when firing. The results of the article contribute to re-evaluating the tactical and technical features of the cannon to propose a plan to preserve, maintain, replace, and improve the service life of the weapon in combat.