The caliber called 315 in India is the 8X57. The Indian ordnance factory used to refurbish military Mauser 98 rifles with maple stocks and sell them as sporters. I have seen their catalogue in the 1970's. The reputation of the workmanship & barrel quality was not very good.

To answer 9ThreeXFifty7's question, without doubt the most popular sporting caliber was 12 bore - whether with bird shot, SGs, LGs or Ball. I have seen old Eley paper cartridges with a variety of slugs.

* Simple round ball that rattled in the case with a cardboard wad under the roll crimp - the wad looked like a washer as it had a .25 inch hole in the middle!
* Lethal ball - a strange looking slug made of 4 pieces of lead that were soldered together - the solder joint stood proud. This was supposed to break up within the animal & create a larger wound channel.
* Conical ball - like a foster slug but no wanes on the side.
* Another strange looking slug (I don't remember what it was called) that was a lead tube with wanes on the side. This was not a hollow point - it had a hole right through it & was reputed to be explosive.

I have no idea what the most popular rifle caliber in India was before 1947. I can't even begin to guess!!