I've shot hundreds of cast bullet loads in my .35 Whelen using Unique, it is very accurate. Don't see why it would not work as well in .30-06, it would be my powder of choice for a plinking load.
I have loaded '06 with 150 grain Berry's plated as well as 173 grain FNGC cast over 14-16 grains of Unique. Great fun! I have some 200 grain .359" RNGC that I could feed to my M98 .35 Whelen. Care to suggest a suitable Unique load?