Thanks for the replies ......
Tried to respond prior to this, but maybe this one will post and not get lost in the electronics! .....
I studied the reloading manuals before starting this thread and I think its a horse race was which family of cases (.308 versus .30/06) tapers more quickly, but I'd forgotten about the .338/06 AI. I wondered if a ridge might be left in the chamber, which ruin cases if not shorten case-life.
I've contemplated for several years whether to build an elk rifle based on the .338 WM (and reduce my handloads, but also have the feature i could shoot factory ammo if necessary), or to build a custom rifle in .35 Whelen or .338/06 (a.k.a. - the .338 O.K.H. - O'Neil, Keith, and Hopkins).
Elmer Keith helped develop that round, but originally based on the .333 caliber. And as mentioned, as good as the .358 Winnie is, many shooters also love it for shooting cast bullets.