From national police reserve 1956@6pp6OKaJiCDIBGD’s (located in Japan) Twitter page:
Below is the Google translation of the Japanese text accompanying the photos, text in parentheses is my attempt to clarify some of the terminology.
“A ninety-nine cartridge of iron (steel) cartridge cases and iron (steel) warheads (bullets) that is said to have been made to save resources. As the two knurls (knurled rings on the cartridge case) show, I’ve only seen it with fictitious (dummy) ammunition.
Since it was hit with a burner when the warhead was welded, the discolored part that was burnt blue remained clearly.
(Concerning the cartridge clip) It’s made of iron (steel) clip. The Type 99 rifle (clip) has a small hole in the center for identification.”