This would be the A6M. It had 2 13MM Heavy Machine guns that replaced the usual rifle caliber 7.7 gun in the engine cowling. An 2 13MMs in each wing with the 2 20MM guns in each wing. My favorite version the A7M had armour plates in the windscreen, one for the pilor and self-sealing fuel tanks and also a water-methanol supercharger. INCREDIBLE PICTURE!! The A6M was built with more powerful Mitsubishi Kinsei engine.