Im certainly no gunnery expert, but heres a few things you can try...
- get up close and personal: i usually only open fire at d200 (d400 if im desperate), dont forget to set your convergence, depending on your usual 'shooting distance'
- small bursts only. Aim, then shoot. Do not 'walk' your tracers onto the target
- go offline (enable lead computed gunsight in SETUP>ARENA SETUP>ENVIROMENT>ArenaSettings, choose FlightModeFlags from list, click change, make sure the LCG is checked, then click OK), now disable friendly lock with Ctrl TAB, by hitting TAB in fligh you can now mark the drones when they are in icon range, itll give you a cross - point you need to aim at to hit the cockpit of the plane, try to get a 'gun eye' - memorize the picture when having a gun solution
- if you run out of ammo too fast offline, change the ammo multiplier to 100000... thatll give you unlimited ammo to practice
- dont fire different gun types at the same time (ie canon and 303) as they have very different ballistics and you probably wont hit with both unless youre really close (d50)