Japanese Type 1 37mm Rheinmetall ammo


I have an article about Rheinmetal AA guns delivered and tested in Japan.

Might be the normal 37mm Flak 18 ammo. To that some 20mm could be seen at the photo.

Is there any japanese headstamped or marked 37mm or 20mm ammo known in collections?

Any idea what the shorter 20mm are?




Very interesting. I would think the ammunition shown is L-R the 37x263B, the 20x138B and the shorter one is the 20x105 Rheinmetall-Borsig.



In looking again at the nice image genkideskan was kind to post, I tried to decypher the spcifications and found myself wondering what unit “t/m” is.

Would that be automatic cycle rate?



This verges on being a wild guess, but I suggest “t/m” indicates “ton/meters” for striking energy of the projectile. Jack


Jack - at around 2200 lbs per metric ton, it does work out roughly correct that this would be the intended measurement unit. The muzzle energy on some of those 37mm loads had ought to be around 40,000 to 50,000 ft/lbs? I know a 20x102 is around 35,900


DK: that’s sort of how my more-rough-than-ready math approached it. And, of I read that chart correctly, those 37 m/m projectiles weight on the order of 3 pounds, which is maybe 5 or 6 times as much as a 20 m/m? Compared to small arms ammunition the numbers are so big it’s hard to judge what is plausible and what is a wild exaggeration. Jack


Jack and DK,


While odd to put it as tons/meter rather than tons x meter, plugging in those numbers gives about 160,500 ft.lbs. That is on par with energies listed for 37x263B rounds. The “1,630g” as grams would be heavy for the projectile and would give about 330,000 ft. lbs. at 740m/s. Having 160,500 ft.lbs. with 740m/s would mean a 795 gram projectile. Perhaps “1,630g” is weight in grains of the HE component?

Jack may well have it as far as the “t/m” goes and that’s an interesting new unit for me! This post earlier had my comments due to my math dysfunction and I started thinking it could possibly be the times/minute loaders must stuff a (6) round clip in the gun. That sort of works too. Perhaps someone on the Forum is able to read the text?