NOOOO. Don't reduce it to 1/2" . To do so would defeat the purpose of a flat shooting caliber (i.e. shooting a long way without having to worry about holdover).
Now, let me show you why going down is the wrong answer. It is called "Maximum point blank range". Let's assume a deer's vital area is 5 inches (it is really bigger but let's keep it conservative). Divide that in half and get 2.5". Let's get extra conservative and reduce the value to 2". That is the distance from line of sight that I want to keep that bullet in. I.E., if I hold my crosshairs on a target I want my bullet to stay within 2" of that point throughout the entire travel.
If I sight in that 130gr .270 fusion so that it is 1.9" high at 100 it will be 2" high at its maximum point of arch at 130 yds, dead on at about 200, and 2" low at just over 255 yards.
If I sight in that .300WSM 150gr fusion so that it is 1.8" high at 100 it will be 2" high at its maximum point of arch at 139 yds, dead on at 225 and 2" low at about 275 yds.
Therefore, the .300WSM gives a 20 yard greater MPBR (Maximum Point Blank Range) using a 2" +- than a .270.
Ok, what does all this math mean for practical purposes? It means that you can put the crosshairs on Bambi's chest center and anywhere from the tip of my muzzle all the way out to MPBR and know that the bullet will never travel more than 2" above or 2" below where the crosshairs are. The flatter shooting a rifle is, the greater MPBR you can get. You can do this math at the range with any rifle and significantly reduce the amount of mental calculation you have to do in the field.
Here is the ballistics calculator I used:
http://www.federalpremium.com/ballistics_calculator/
