I get a lot of questions on the 400 Whelen these days, and I am installing several new barrels this fall as well. Two questions are most common; Firstly it is, How does it feed, and Secondly, how hard is it to make?
I use the G&H reamer made by Manson and G&H dies made by CH4D.
This being the Gunsmithing section, Feeding goes first;
One sentence; The 400 Whelen will feed Hornady 400 grain bullets, from any 98 Mauser, and any other long action, without any alterations. Although, for the Mauser, tweaking the right receiver feed rail a bit with a ball end mill makes them stack much better, but still, it will work without doing that.
As for making brass, today I made some from LC Match; expand them with a plug which I provide with the barrels, and size in the CH4D sizing die. That's it.
Yes there is more than enough shoulder for headspacing; stop asking that.
It is really a very easy wildcat to manage in every way.

I've always wanted one! Keep us posted.

Assume Woodleighs would be just as easy to feed.

Nothing else left to post; I have build many of them and this is just some thoughts while I do the next batch; Six of them.
If you want one, PM me so I can put a barrel in the que.
It is an easy wildcat to manage, is the point.