Yes virtually identical, Jack O'Connor and Fred Huntington used to turn the belts off the 460 WM cases and load them for their 416 Rigbys.

It seems the idea in this post is to end up with a case slightly swaged down from the 416 or 460 parent case. Not sure what that achieves as the end result will still be so close to the parent case that any changes to the action to accommodate anything resembling a 416 will be the same?