Heya Sparks! <S> buddy. First, make sure your convergence is set for each plane you fly. I prefer setting mine up in the 375 to 400 range. Sounds like you are waiting to take your shot at the right time, i.e. 450 and closer. Like everyone else said, practice and lots more practice. Taken me 2 years to get my gunnery a consistent .10% lol.
"but I am finding that in a turn even having the target in the bottom of the sight is not pulling enough lead - I have even tried having the target under the nose out of sight but that did'nt work."
Keep trying and remember that gravity is affecting your bullet path, and also in a turn your bullet is going the direction the plane was at the instant of firing, while your a/c continues through the turn. In a hard banking, hi speed snap shot such as this, I also aim a little hi as well as have the bogey completely out of sight under the nose, the icon just barely visible, and this is in zoom. You can see the hits (an obvious bug, but usefull hehe) through your instrument panel, and occasionally the enemy will 'ghost' in and out of view. Just keep adjusting your lead until you see the hit sprites, then I pull a touch more and relax back pressure so the bullets are more concentrated and not spread out, and let the enemy fly into your bullet stream. Carefull not to go to far and bleed all your E trying to follow him, just straighten out, extend and come back for another pass. And as was stated earlier, the cannons are more susceptable to gravity and drop off a lot quicker than do MG's. Most of my snap shots the cannon shells miss and the .50s do all the work.
I use the zoom religously, and effectively I think. I have it mapped to a button on my throttle to quickly toggle it on and off. I set the amount of zoom to about half of what is available(P38, adjust if differently for other a/c), still affording me a small amount of instrument visibility, mainly the airspeed indicator and the ammo count. I'm only zoomed in when I'm on his six ready to fire, or need to see which direction his a/c is pointed, then it's back to regular view. It's easy to get 'target fixation' tho in zoom mode, and that has caused a quick ending to many of my flights LOL.
As far as when you are closer and
"the target is flying top to bottom and side to side across the sights soooo fast that I start over controlling because I always react that bit too slow and finally overshoot."
you either need to chop the throttle, dump flaps and slow to match his manuevers, adjust your attack ahead of time, or you have to anticipate where he will be and try to get your shot at that point. Or you overshoot,extend, make another pass and see if he will do the same thing again, if so, you've got him because you can set up your shot. Most of the time it's better just to extend (or us a vertical manuever) and come back when this happens, so you don't blow all your E and find yourself in a deffensive position.
Something else that is important is having your trim set properly for the speed you are at when taking/correcting your shots. If you are badly out of trim, the nose is gonna be 'jumpy', not quite corresponding to your intended stick inputs. I also have my trims, all of them, mapped to a couple of hats on my throttle and am constantly ajusting aileron and elevator trim through out my engagements. Sure helps for 'steadying' the nose so to speak for shooting.
And last but not least, use short bursts, don't just 'spray and pray'
If you see the hits, keep pouring it on till they go down or move out of range, but just don't hose away at will. Pump out a couple of short bursts and hope for a lucky shot until your confindent a steady shot is there.
Oh yeah, more practice and lots of patience.
ts