Japan produced a number of machine guns that were direct copies of the British Lewis (Japanese Type 92 machine gun) and Vickers machine guns including the ammunition.
These were primarily used in Navy aircraft.
The 7.7mm cartridge used by the Japanese versions of the British guns is a direct copy of the .303 British (7.7×56mmR) rimmed cartridge and is distinctly different from the 7.7×58mm Arisaka rimless and 7.7×58mm Type 92 semi-rimmed cartridges used in other Japanese machine guns and rifles.

Ball: 174 grains (11.3 g).
Cupro-Nickel jacket with a composite aluminium/lead core.
Black primer.

Armour-Piercing.:
Brass jacket with a steel core.
White primer.

Tracer: 130 grains (8.4 g).
Cupro-Nickel jacket with a lead core.
Red primer.

Incendiary: 133 grains (8.6 g).
Brass jacket with white phosphorus and lead core.
Green primer.

H.E.: Copper jacket with a PETN and lead core.
Purple primer.

Note: standard Japanese ball ammunition was very similar to the British Mk 7 cartridge.
The two had identical bullet weights and a "tail-heavy" design, as can be seen in the cut-away diagram.
Japan produced a number of machine guns that were direct copies of the British Lewis (Japanese Type 92 machine gun) and Vickers machine guns including the ammunition. These were primarily used in Navy aircraft. The 7.7mm cartridge used by the Japanese versions of the British guns is a direct copy of the .303 British (7.7×56mmR) rimmed cartridge and is distinctly different from the 7.7×58mm Arisaka rimless and 7.7×58mm Type 92 semi-rimmed cartridges used in other Japanese machine guns and rifles.
Ball: 174 grains (11.3 g). Cupro-Nickel jacket with a composite aluminium/lead core. Black primer.
Armour-Piercing.: Brass jacket with a steel core. White primer.
Tracer: 130 grains (8.4 g). Cupro-Nickel jacket with a lead core. Red primer.
Incendiary: 133 grains (8.6 g). Brass jacket with white phosphorus and lead core. Green primer.
H.E.: Copper jacket with a PETN and lead core. Purple primer.
Note: standard Japanese ball ammunition was very similar to the British Mk 7 cartridge. The two had identical bullet weights and a "tail-heavy" design, as can be seen in the cut-away diagram.
.303 British