Thanks. I purchased the rifle from a gentleman in Melbourne who in turn, picked it up from a local auction. That is as much as I know about its history, but it was possibly one of the many doubles which made their way to Australia from India years ago. Exact date of the rifle is not known, but going by its London Proof House marks it would be early 1900's (from 1904).
The current load I am using is 75gn AR2209 with a Woodleigh 400gn RNSN bullet. Bullet dia is .408".

Chris