If you don't already have tracer on, do so, at least for GV's - it makes a major difference, IMO.
M16 - use short bursts to establish lead, then longer bursts to finish them off.
Ostwind -
Don't use the gunsight! I've set my gunner position up as high as it goes and only aim by tracer. I've hit at 1.9k with this method (but for some reason I seem to miss more of the <500 shots
)
You have plenty of ammo in the Ostie to keep firing once you have a good solution.
The reason I don't use the gunsight (for flying targets) is I could never see the plane when I had to lead it.
Cheers