Re: .338 calibers
Allen precision on here does an excalibur improved. Several smiths do the 338-378 wby and imp versions, 338-416 rigby imp and similar case capacity rounds. Those are as big as you can get before getting into the chey tac case which requires a much heavier rifle.
Depends on how heavy a rifle you want, barrel life, distance you want to hunt, etc. Let us know what your purpose is for the rifle and guys on here can help you. I backpack hunt and want a rifle I can carry all day comfortably. The Mcmillan EOL Outdoorsman I have been testing is a 1000 yard capable rifle that weighs 7 3/4 pounds and it is hard to beat that. Tons of criteria you nee to look at.
Predictions are difficult, especially when they involve the future