7.7 T99 and Japanese aircraft MGs

Japanese aircraft MGs used 7.7x58SR ammo (type 89 and 92) for the Army and 7.7x56R for the Navy.
However, it is often reported by 1943 the production of type 92 ammo ceased and only type 99 remined in production. On the other hand, 7.7mm MG were used by IJA aircraft till the end of ww2. This raises the question of what ammo was used for these MGs - did they use type 99 ammo (although, to the best of my knowledge this existed only in Ball, AP and Tracer loadings - not in Incendiary nor Explosive version which were favorites of the airforce).
Has someone more info on this?

By 1941, the Army had prototypeType I nambus MG in T99 cartridge. The gun was lightened and improved on the T92 heavy Ground MG.
They also developed a Type 1 Flexible Gun both single and Binary based in the Type 89, againin T99 cartridge.

But they found by practical battlefield experience, that a T92 gun would feed AND extract T99 cartridges in firing.
So this is probably why T92 ammo may have slowed down. I don’t know if the Vickers army air fixed guns could use T99 rimless ammo…the T shape of the Gib piece may have been insufficient for the smaller rim…instead the massive claw extractor of the 89/92 guns could easily handle the smaller rim and deeper extractor groove of the T99 case.

As I have not seen a T92 strip packet dated after 1943, I can’t confirm or deny the 1943 cut off date…most of the T92 ammo in the US is 1938-39-40, left in China at the end of WWII, and only released inthe 1980s.

Interesting Post question.
Maybe Ken Elks, Francis C Allen, or Mr. HONEYCUTT
May have info.

Doc AV

The question of the Vickers E clones using T99 is indeed quite interesting as these MGs remained in use in the Far-East theater of war…till the Korean conflict.
There is a “strange” US document found in the Japanese national archives:
Amount of arms, shells, and motor vehicles production chart. Report No. 45q(14), USSBS Index Section 2. "
It includes production data for IJA Aerial ammunition and concerning the 7.7mm this is what it gives (in thousands of cartridges):
1941 M89 Ordinary 1500 M92 AP 1500 M92 Incendiary 1000 M92 Tracer 1000 M99 Special 800
1942 M89 Ordinary 900 M92 AP 700 M92 Incendiary 600 M92 Tracer 600 M99 Special 400
It does not gives data for 1943/44/45 and it mentions this “M99 Special” (there is a mention in a modern Japanese source saying that the “Ma-101” “Special incendiary” - ie explosive - bullet was officially adopted in 1940 as type 99 special bullet.)