The most important thing is that once you set your convergence, 95% of the time that's where you should open fire. With some exceptions your rounds will be clustered right around your boresight (there's a couple aircraft that I believe are slightly off-center, IE the Zeros). At that point it's not a matter of how much to adjust for bullet drop at a given range, but how much lead to give the target when deflection shooting at your established firing range (for which there's TONS of math to calculate, but is much easier to get from dead reckoning of the sight picture after enough practice).