Whenever you double the diameter of a circle you don't double it's area - you quadruple it. So going from a .257 caliber ( 25-06 ) to a .277 calber ( .270 ) is actually a bigger step than assumed.
But you aren't going from a 25 to a 50 caliber, so he is not doubling the diameter, or quadrupling the area. It is only a 16% increase between the area of a 25 and a 27. There is a 23% increase between a 270 and a 30'06. So the 25 and 270 are much closer than the 270 and 30'06.
BUT...You can shoot heavier bullets in a 270, and if I owned a 270 I wouldn't shoot 130's, I would shoot 150's on bigger game. And that is something the 25 cannot do.
