Which fuze is used in 30 mm high explosive incendiary (HEI) ammunition?

The M505A3 is the correct choice for the fuze used in 30 mm high explosive incendiary (HEI) ammunition. It is a mechanical time fuze designed specifically for this type of ammunition, allowing for effective detonation upon impact or at a predetermined time after firing. This design plays a crucial role in maximizing the explosive effect of the HEI round on the target.

The other fuzes listed do not fit the specifications or intended use for 30 mm HEI ammunition. For example, the FMU-154/B is primarily used in different types of munitions, such as precision-guided bombs, while the M23 and IMP-124 serve other specific functions in munitions systems that do not relate to 30 mm HEI ammo. Understanding the specific applications and compatibility of these fuzes is vital in munitions operations, ensuring that the right fuze is matched with the appropriate ammunition for optimal performance in various combat scenarios.