If this is a gunnery question concerning BnZ, and you are attempting to find a sweet spot convergence to solve the three primary problems affecting high speed gunnery. Then consider Hitech has modeled gunnery historically. Even if we want to stretch the physical limits. Shooting down other small fast fighters, your effective maximum range is 1200ft. Even with cannon rounds. Yes the chemical content increases their range. Longer range decreases their odds of hitting anything as small and fast as a fighter.
In ww2 average convergence for wing mounted guns was 250-333. HUB cannon were stuck at 0 incidence, and planes like P38 and mossi were harmonized with the sight line to drop back into it at about 1600ft. Past 1200ft, dispersion makes hitting a tiny fast fighter less probable as a full time tactic. Bombers are another discussion. Even then a 50cal slows down by 2\3 and looses half its kinetic energy by 1200ft. After 1200ft where it drops 4ft, it begins dropping through the basement and dispersed. So in P38 the ganging of the 50cal allowed it to reach out to 1600ft but, you are still loosing kinetic energy badly in terms of penetrating armor. The same problem will exist for a 20mm AP and you will start getting more skin surface detonations than internal after penetration. Wonder if Hitech has a formula that accounts for 20mm lack of penetration past 1200ft on a graduated line? You see as many ww2 bomber damage photos where it's obvious the cannon round exploded after penetration as you see explosions where the aluminum skin was warped and curled up.
In ww2, guns were harmonized to the effective combat range of the round used. Since Hitech reasonably models this in the game. I would venture the OP is having a gunnery problem related to firing from a higher position down, and the aimpoint. Calculating lead and deflection for the target as it turns under his down pointing nose. And accounting for the effect of his increased speed in the dive on where his rounds will really end up.
After action reports and film, showed the vast majority of kills were made at, or inside of 1200ft on both sides of the conflict. Bombers by the virtue of their size and slow speed are another discussion. Including how slow average bomber combat speeds were opposed to ours in the game. Still, surface area counts as your rounds disperse wider past 1200ft.
