Daryl,
I believe the 416 Ruger to be about in between the Taylor and the Rem Mag (approximately). My thoughts were to start on Taylor loading data and go from there. Basically it is a beltless Taylor, about 70 thou longer with less taper.
I'm thinking AR 2208 (Varget) and RL-15 would be good starting points.
Just wondering who else might be handloading for one at the moment.

DC