It is a gradual retrogressive process in the use of a gun barrel from being brand new to being finally discarded as useless.

• 火炮身管从开始使用到报废是一个逐渐的过程,以前没有对此过程划分等级,现在随着火炮威力的提高,研究身管性能等级问题就显得尤为重要了。