Hi, I bought the above rifle a couple of weeks ago and have just got all the gear to load for it

I'm a competent reloader for my modern nitro guns but don't have a clue were to start with this one, can't find any load data!

I'm using Aussie brass, 500gr cast bullet and FFG 777. Can't use blackpowder at the moment and I want to stay with the 777 as I have a good source.

Any ideas