type5-30mm-machinegun

Japanese aircraft guns: top - 37nun Ho-203, middle (front) - 20mm Type 99-1 flexible (note perforated barrel casing and forward-sloping grip), middle (rear ) = 20mm Type 99-2, bottom - 30mm Ho-155 II

http://www.bevfitchett.com/heavy-machine-guns/the-japanese-miscellany.html