Another variable that many people dont consider is the magnification of your scope or its mildot spacing is rarely true, to get an acurate measurement of your scopes actual mag at any given setting on the mag ring you should high light the inch increments on a ruler with a marker pen and then put this out at around 27 yards for measuring at 10x mag. At 10x mag the mildot spacing should coincide with 1" at 27.7 yards, keep moving either yourself or the ruler untill your dots line up with the marks on the ruler at the mag you use then accuratly measure the distance, for chairgun it is best to measure from the end of the barrel to the ruler, then the mag can be tweaked in CG untill the dots coincide with inches at the distance you measured. Then you can note the actual mag your scope or to be more accuate the mag to use to get the correct dot spacing that it is set at in CG and use this for that mag setting on your gun when doing CG calcs.
Scope mag can change slightly when the px is brought into the short distances that we use in HFT or the mildots may not be quite truely spaced, either way this method will bring your actual dot spacing into line with the program eliminating another variable.
Also the physical centre to centre measurement of the scope height is not always correct as the zeroing of the scope involves moveing the erector tube within the scope, this can make the light path enter the scope either above or below centre, i also use the method described by Dia6olo above to find the correct height to use.
Tommy, i think that gun of yours is achieving a higher bc so you should do some down range and at the muzzle velocity measurements to establish exactly what your bc is. you can borrow my down range chrono if you like? Then measure your scope dots and then use the method described earlier to determine the actual scope height, that should get you closer to whats happening.
But when it shoots as flat as it does i would,nt worry about it, just use it!!