Get a tapered expander and lube the inside of the necks prior to sizing. I would use new brass. No reason to shoot it in the 06 prior to sizing to 35 cal. I would fireform the cases in the Whelen before getting into serious load development. Seat the bullet hard into the lands and use a medium load of one of the faster burning powders listed for the Whelen. Other methods will work but this will let you get a preliminary scope adjustment, some good trigger time and let you get use to your new rifle.Rick.
