(1) scope height
(2) Average muzzle velocity (from a 10-shot string via a chrony
(3) Average pellet weight
I take the pellets that I will be using for that particular rifle and weight them in my gun powder weight scale (accurate to 0.01 grain). Then I shoot them via a chrony to get the average velocity. This will be my muzzle velocity for input into Brad�s software. The accuracy of the above inputs is important.
Input the above info into Brad�s STP software and you should see the apex of your pellets trajectory. The apex is the highest point of your rifle�s pellet trajectory path (See next Figure). For example, the Figure below shows that the apex is at 27 yards. When you use Brad�s STP software, you have to type �27� in the �ZERO RANGE� field on the left, then click Calculate Trajectory button. This will re-calculate the trajectory and show that the apex or zero point is at around 27 yards. For your rifle and scope, it may not be 27 yards. If this is so, all you have to do is enter a distance (into ZERO RANGE field) that you think where the zero point is at. Keep doing this until you see only positive numbers in the �Clicks U/D� column. These positive numbers means to adjust the elevation setting to �up�, negative number means �down�.
The apex is where you set your rifle scope to zero. Let just say for now, your scope zero at 27 yards. We will use this number later. When you shoot at any other distances, you only need to do �up� adjustment in your scope�s elevation knob. This makes your task simpler, because you don�t have to worry about which distances are down setting and which are up. They are all up settings. In Brad�s software, you print the turret settings. These turret settings are your elevation turret settings for your scope. You should print out from ranges 10 yards to 60 yards (70 yards if you like). Now, tape this piece of paper to you gun or scope so that you can refer to it during an FT match.
