There are a lot of things that can influence the size of the hole. There is bullet type, speed, bullet size itself and whether or not you hit bone and also how close or far away you are. I shot a doe a few years ago at about 20 yards away with my 270 and 150gr bullet and the entrance wound was only about the size of the bullet, the exit though was the size of a football. I hit a rib and it really tore up the other side of the deer. Lets just say that the deer didn't move a bit after that hit. The reason for the close shot, we met each other at the top of a hill and where both surprised lol.