what the hell kind of gun is this?

The beginning, when the Aussies are forcing the Japanese to dig up the murdered. It's skinny like an Austrian Steyr, got a clip on top like a warped Sten, and a forward handgrip. This clip, from 7:03 til 7:35.

https://youtu.be/LcgPexeOZKI?t=423


Do not go gentle into that good night,
Rage, rage against the dying of the light.