This study presents an analysis of the fixed biases and variable errors affecting gun fire. The emphasis is placed on automatic cannons being developed for use as main guns for armored vehicles. It is proposed that barrel bend has been overlooked as a primary cause of inaccurate fire and that automatic cannons will be particularly susceptible to this condition. A formula is derived for approximating the magnitude of bend that can occur. A model is presented for estimating miss distance in the plane of the target as a result of fixed biases (including barrel bend) and other variable errors. A parametric analysis demonstrates the magnitude of resulting miss distance. Methods of avoiding the effects of barrel bend are presented.