Any 338 Whisper shooters on here? Considering a build

I'm looking at building myself a dedicated suppressed bolt gun, and I'm leaning towards a 338 whisper. I have a 700 action (.308 bolt face) to work from, and I'm trying to figure out sources for components, dies, etc. I know it's necked up 7BR brass, but have read that it can also be made from .308 brass. I've never gotten into forming my own brass, so the idea is all new to me.

Anyone have any experience with this cartridge? Know the twist rate SSK uses for the 300gr SMK's? Still trying to decide if this is a viable project or not. Looked at other calibers, but this seems to fit what I'm after better- providing of course, that the components to build and shoot it are actually available... Input, Thoughts?