Unless your 338 win mag dies have a tapered expander, which they likely don't, you'll probably do more damage by running the -06 brass through them first then just running them through a 35 whelen die with a tapered expander. I've litterly opened up 100's of -06 cases to 35 whelen, and so long as you lube the inside of the neck, you'll never loose a case. 270's and 280's can be troublesome, but the -06 will open up every time.
