[Tony Williams]

Originally Posted by rldunn

This suggests there was no such victory prior to May 43 (such as Schoenert's victory on 21 Apr 43). This would leave the Japanese as the first to employ this arrangement. Is this your understanding?

It's not clear. This is why FG:WW2 has to say:

Upward-firing gun installations were developed almost simultaneously in Japan and in Germany. As we have mentioned before upward- and downward-firing guns were installed on several Japanese heavy fighters, both for day and for night operations. However, the Japanese were rather uncommunicative towards their allies, and it must be acknowledged that also in Germany itself several people had submitted the idea to the authorities. One Ir. Poppendiek even proposed a battery of six to eight cannon, which would be triggered by an infrared sensor if the fighter flew below a bomber. Combat experience also contributed to the concept: Occasionally, Bf 110s had flown below the bombers, and opened fire with their flexible guns.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk