Yes, the Vortex Precision Extended Cantilever Mount will work on a Ruger Precision Rifle in 300 Win Mag. However, the exact model you need will depend on the specific model scope you are planning on mounting to the rifle.
Just spoke to vortex, they said the RPR 300 Win Mag already has a 30 degree cant on the rail, so a zero cant model is the one you want,,,,,,just my two cents,,,,thanks,,,Dave