Firing port

Some pistol ports, such as on the Sherman, included vision slits such as "protectoscopes" increasing visibility around the tank.

Ballistic weakspot

Being a ballistic weak spot, firing ports are often reinforced with additional armor, and in subsequent designs reduced in number (BFV), or deleted altogether (Sherman and Tiger I [January 1944]). Other armor is improvised such as slat armor to stop shaped charges or chicken wire to stop grenades.

However, due to strong crew demand, they are sometimes brought back, as happened with the Sherman. This was in part due to its use during ammunition resupply in the Sherman, eliminating the need for an additional crew member to pass ammunition through the loader's hatch, instead of being able to simply pass the ammunition from the ground through the firing port.

One of the Tiger I's firing ports (right) was converted into a loader's escape hatch and the other covered with an armored plug and eventually deleted from the design to improve production time and reduce costs.