The Type 99 cannon suffered from relatively low muzzle velocity and rate of fire compared to other 20mm cannons but the trade off was an extremely light cannon that did not hinder flight performance of the IJN's fighter aircraft. The close economic and political ties between the IJN and Dai Nihon Heiki KK ensured that the latter had little competition.
The Type 99 cannon, despite having a relatively low muzzle velocity and rate of fire compared to other 20mm cannons, was extremely light. This made it suitable for fighter aircraft without hindering their performance. The close economic and political ties between the IJN and Dai Nihon Heiki KK meant that the latter had little competition.