The A5M family included successive carrier versions, a two-seat trainer, and proposed or experimental forms for other shipboard roles. Japanese engineers also tested 20 mm motor cannon and Oerlikon weapons as alternatives to the standard pair of 7.7 mm machine guns. Heavier firepower brought more than the mass of the gun and ammunition: the airframe needed reinforcement and had to absorb recoil and vibration. Those penalties threatened the speed that Jirō Horikoshi's team treated as the design's central advantage. The choice was between greater hitting power and the structural weight that would erode performance.
Chapter · 27:07-29:29
A5M variants and the cost of heavier cannon armament
Carrier, battleship, trainer, and experimental variants tested how far the A5M design could stretch without surrendering its speed advantage.