Which type of fuze can prematurely explode when fired in heavy precipitation?

The M557 fuze is designed to be used with high-explosive projectiles and is known to have a sensitive mechanism that can be affected by environmental conditions. Specifically, it is susceptible to premature detonation when subjected to heavy precipitation. This is due to the moisture causing certain physical or chemical reactions within the fuze that can lead to an accidental explosion during or shortly after firing.

In contrast, the other fuzes listed—M551, M757, and M782—are designed with features that mitigate such risks under moist conditions and are not typically associated with premature explosions due to heavy precipitation. Each fuze has its own operational characteristics and intended applications, which is why the M557 stands out in this scenario regarding its sensitivity to weather conditions. Understanding these distinctions is crucial for ensuring safe artillery operations, particularly in varying weather.