Mysterious Zero-sen!!!

Mysterious Zero-sen!!!: The Zero-sen is the most thoroughly documented Japanese airplane yet there are still some quite surprising, small, less known details and information.
Here we present photos of one of the least known Zero-sen subtypes.

Asahi Shinbun, July 25, 1943. Photo taken by reporter Hashimoto. Note that this Zero has A6M2 wings, A6M3 cowling A6M5 long barrelled 20mm wing cannons and early drop tank.

While the initially very successful A6M2 Model 21 type was dominating the skies early in the Pacific War, Mitsubishi was already striving to improve performance. Various modifications resulted in the A6M3 Model 32 with different cowling and shortened wings. The most important difference with the previous model was the new Sakae 21 1,130hp engine instead of the Sakae 12 of 940hp. Unfortunately the new A6M3 was not particularly successful and production was terminated after 343 units were delivered.
(Illustrations by "Fuku-san", HERE)

A6M2 Model 21

A6M3 Model 32

While the A6M3 proved to be a failure, the new engine turned out to be rather promising so an interim model keeping the A6M3 cowling and engine but on an A6M2 fuselage started to be produced. Some were with the shortened wing cannon similar to the A6M2 but some had a longer barrel version of the 20mm Type 99 cannon. 560 units were produced of this interim type which was superseded by the new A6M5 Model 52, the first flight of which was in June 1943 and was officially accepted two months later.  

  A6M Model 22 (interim)

Very early A6M5s were externally similar to the interim A6M Model 22.

A6M5 model 52 (early production model)

A6M5 Model 52

This A6M ready for take-off from a Rabaul airfield has all the characteristics of the interim A6M2 Model 22 but also 30kg bombs under the wings.