convergence plays a big part in that. when i first started i mostly used a convergence of 350 yrds for 20mm cannons and 400 for 50cals. this was usefull because the majority of my kills were chasing enemies or cherry picking unsuspecting foes. i had niether the knoledge or the skill to provide any other shots. I was generally either on somebody's tail and getting a kill, or squirming around and being killed myself. As I slowly improved my dogfighting tech, i found myself producing alot more snapshots and crossing deflections, and after a long while i changed my convergence to 300 as a maximum. more time went by and i developed alot of reversal moves, and learnt the basics of scissors and angles. these days i set all convergence for 20mm cannons to 175-200 maximum, and 200 flat for all types of MG rounds.
there are pros and cons with this change. i find it alot harder in general MA use to kill people at 400 yrds, something i used to do with ease, but on the plus side snapshots and quick crossing deflections were more within my reach, and a kill more likely to be registered to me rather than an assist.
long story short, play with convergence, work out the ranges and angles that you most often provide and set sonvergence accordingly, you might be pleasantly surprised with the results.
above all, keep practicing and dont lose heart.