Nosler has some .416 Rigby data for the 400 gr Partition in their current reloading manual. I don't believe Nosler lists all of their loading data online.
Here's some 416 Rigby load data with the most accurate powder in our test barrel. This data is from our Nosler reloading Guide #5.
.416- 400gr Partition
Federal Case
Fed 215 Primer
IMR 4350
Start: 88.0 grs (most accurate)
Max: 92.0 grs
As always start low and work your way up carefully.