Gryphon,this data is in a book by Sam Fadala,an author of 11 books on hunting and editor of various hunting,reloading magazines.Now i have not personally tried this out i.e.zero at 25 yds.and measure but i have used both calibers extensively and found the 7mm.mag.to be a flatter shooter as compared to the 270 at 300 yds.As far as energy in ft.lbs. is concerned it is definately more.
If you manage to get hold of Fadalas book,The Riflemans Bible it is on page 66.