What must be checked regarding the firing pin before using the mortar?

The correct answer highlights the importance of ensuring that the firing pin is properly installed in the breech cap before using the mortar. The firing pin is a critical component in the mortar's firing mechanism, as it strikes the primer of the cartridge, igniting the propellant and initiating the launch of the projectile. If the firing pin is not correctly installed, it may fail to strike the primer effectively, leading to misfires or failure to fire at all, which can compromise the safety and effectiveness of the mortar system during operations.

Additionally, while factors such as rust or appearance might seem important, the fundamental concern is the operational functionality of the mortar. Ensuring that the firing pin is properly secured in its designated position is crucial for reliable performance and safety during use. In practice, maintaining the integrity of each component within the mortar assembly, especially the firing mechanism, is critical to ensure that the system operates correctly when needed.