Re: Cosine Indicator
With the example I wrote previously:
<font color="red"> 10.63 MOA - 2.954 MOA = 7.676 MOA (corrected MOA you'd now dial) My RSI Ballistics Lab program for example predicts the corrected drop to be 7.68 MOA too.
Now instead, use the method that takes the bullet path MOA and multiply it by the cosine of the incline angle.
What you get is 8.7 MOA not 7.68 MOA... which is a 7.8" deviation at 770 yards... Now remember, none of our rifles shoot one hole groups at 770 yards, so factor in the additional error due to the rifle and your inability to shoot in one hole at that range and you have the true picture. Did you miss? At 1200 yards it would be MUCH further off than that, using this method it would... even further off multiplying the range by the cosine for a "corrected range"... this is just a fact.
The steeper the angle, and/or farther the distance, the more error these two methods introduce.
How precise do you need to be? Or really, at what point do you find out the method you've been using has failed you as a result of their inherant inaccuracy.
Your calculation <font color="red"> 1.0 minus 30 degree cosine of .87 = .13 X actual drop of 5.73 MOA = .745 subtracted from 2.9 MOA bullet path = 2.2 MOA </font> is correctly done.
Sorry I wasn't more clear.
The angle should be in reference to the bore line, and set to zero when leveled... has nothing to do with some angle the scope tube happens to be setting at, 20 MOA base or not. The asymmetrical force of gravity changes trajectory when we change the bore angle from the level fire position, which is 90 degrees to this force of gravity.
The 20 MOA base only allows you to elevate the bore line more while maintaining the same POA, or thus compensate for more bullet drop etc.