You are kiddin' right? If an one arrow is wider than another, there is more surface mass (Not weight mass). If the same "weight" arrow has more "surface" mass it will take more KE for a pass thru.A smaller "surface" mass arrow, will out penetrate a larger "surface" mass arrow of the same weight every time. This, considering you do not have a 2" cutting surface trying to plow all the way thru a deer's body. I am speaking of using Fixed heads.

Sorta like trying to shove a greasy BB up a Bull's ass compared to shoving a bowling ball up same said Bull's ass. It will slide in a lot easier if it is smaller.

LT