Another wrinkle...
I recognize this is a step backwards, since it's a bit slower and I'd be stuck with Hornady brass, but anyone ever played with a 338-375 Ruger?
To keep it inside a standard long action at 3.34", I'd have to push the shoulder back a bit, giving up a little capacity. Not sure how far I could neck down without pushing the shoulder back before the neck would get too short yet, but I'd try to run it as long as possible given the brass. I'm speculating around 2850fps with a 250grn pill out of a 24" tube, pick up a bit if I go longer barrel (which I plan to). I'd guess I'd hang around 98grn H2O in the case - so giving up quite a bit to the Edge and Lap, basically splitting the difference between those and the 338WM.
Maybe it's just the Ruger fanatic in me coming out, as there's really no reason to wildcat off of a such a new proprietary case, other than it'll be a little easier working south of 3.6" COAL. I've done ok feeding .416Ruger out of 300wm mag boxes - keep the COAL short enough on a 338-375R, I can feed it from a DBM.
Thoughts?