If you're shooting 225 gr. Sierra Game King of Nosler BT you might want to try IMR 4064, those bullets shoot very well in my .35 Whelen with 4064. 200 gr. bullets give great accuracy with IMR 3031 in my Whelen, don't know if either powder is applicable in the .350 Rem Mag you might want to check it out.
For whatever reason most load manuals favor different powders for the two in spite of the similarities. I don't know if there is a real reason for this, or if it is only because they quit developing data for the 350 in 1974.
