It is an 8mm calibre, but it's some archaic, rimmed design. I can't remember what the "normal" name is for it.The "315 Sporting" is curious too. It looks like an Enfield and has the sloping magazine base that would indicate a rimmed cartridge, but is claimed to be in 8mm calibre.
AGH!!!!!!!!! I spent 3 months working in Pune India 2013 and went often to the olympic range there, they insisted that all used .22lr cases were handed back in to prove that no live ammo had left the range. They were very funny about any civilian ownership so how this wally got that rifle I can only imagineHere's a clip of the Enfield based one with a demonstration of safe practice in gun testing. This one is useful as if you let in run to the end it flows into two other videos on Ishapore rifles and stuff.