Those Japanesetraining rifles were intended for the Japanese equivalent of high school ROTC, not for issue to troops. They were not meant for firing live ammo and of course, no live ammo was ever given to the school kids who used them. I have three, and two will not accept a live round, apparently being made for a special short exercise (dummy) round, not a blank. The third will accept a live round, but I have not fired it. All have barrel bores so oversize that even if a live round were to be fired, there would be very little pressure.
(FWIW, when I saw that cartridge case, I thought it was from a pressure testing gauge, since it looks just like one.)
Jim