Help please how do you aim the 30mm 37 and 40 what convergence and anybody got any custom gunsight's for firing the 30mm.I wanna learn how to aim the p39 for snapshot and I cant hit a a bomber from 200feet out from this thing I can just takes like 10rounds just to hit it. 
I cant speak for the larger guns, but hitting with the tater, in my opinion, is more a product of position and timing than raw "aim," as evidenced by my inability to hit anything short of an aircraft carrier in a dead six position.
The dispersion of the rounds is so great that trying to be a sharpshooter with the 108 is pretty difficult. The longest tater shot I ever made was in excess of 650 meters and it was blind luck (it was also Pacer
). Typically, I dont fire until within say... 250 - better still under 150.
Against all aircraft, you need to be able to predict the flightpath of the EAC and position your nose, with your wings perpendicular to that flight path, in such a way as to allow for a crossing snapshot. "Continuous lead" shots are difficult and I wont even waste my time (or ammo) pulling the trigger, frankly.
The requirements are slightly less strict in a 262, however, as you have four guns as opposed to the K4's or 152's single hub gun. In that case, you can be more liberal with your trigger finger.
Two great pieces of advice I received were (credit to moot and grizz) "aim to hit with the first round" (in single-30mm AC) and "expand the convergence differential" (in 262).
That is, when you fire that snapshot in the K4, throw 3-5 rounds out, maximum, and aim to hit with the first. Surprisingly, this leads to much better accuracy (for me, anyway).
With respect to the 262, a separation of about 50 yards between the upper and lower guns provides a great shotgun effect - with every round being potentially lethal. There is, in other words, no reason to use a narrow cone of fire as you would with 50's.
Practice makes perfect, as with all things. It would not be a waste of your time to simply log in in "offline" mode and experiment with convergences, lead, etc against drones. Cant hit something pulling evasives until you can hit something relatively straight and level.
EDIT: To echo some other comments, I also avoid buffs in the K4. While it may have been fantastic in WWII for putting maximum destructive power in the air in a minimum amount of time, you need to consider the differences between how buffs were attacked in reality - and in AH.
In reality, you made a single pass, usually head on, 95% of the time. Theoretically, this freed you to loose all 60 rounds at a single target before bugging out.
Since a single pass and a bug out is no fun (and we cant die paying a game), the ammo load is insufficient, in my opinion, to deal with anything more than say... three buffs... if the 50's dont knock out your radiator, first.
As has been previously stated; I'd rather have a Jug or even a Corsair for the task and I'd even leave the cannon Hog at home. If I had an A8, I'd rather use the 4x151/20's than add 30's to the mix. 4x151/20's is more than enough firepower to hit any bomber hard enough to pop it and it doesnt matter how destructive the 30 is, by comparison, if you cant hit with it.
