Help in IDing this 20mm? cartridge

#1

Looking for input on this cartridge.

Steel case, headstamp 2403 44 W9. Projectile measures 13.5mm at the red band, 12.8mm on the main body, and is stamped, eet 110/44.

TIA

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#2

German 13x64mmB

#3

Used in only one gun: the Rheinmetall-Borsig MG 131 aircraft machine gun of WW2.

That projectile is an armour-piercing incendiary.

#4

Didn’t the Japanese have a percussion version of this too?

#5

They did and so did Germany. Just the Japanese had problems in manufacturing electrical primers.

#6

Elk suggests they were weary of electric primers in the humid tropics,i guess variable storage and potential reliability issues.