ok at the risk of sounding stoopid 
I live in Australia and my ping is usually 250. If I am fighting a guy who lives next door to AH's server who has a ping of say 50, does this mean his aircraft is actually 200ms (250-50=200) further ahead from what I see on my screen?
The reason I ask is when I practice gunnery in offline I get the deflection required to make hits, but then taking that into the MA, what seems like a simple shot, i.e. a con plane filling my gunsight and sometimes all my windscreen, my pipper is aimed at his cockpit as he has just stalled and is hanging there like a cherry, I pull the trigger pouring rounds into him and nothing happens .. he flies away and I am left in bewilderment.
Or is this rubber bullet syndrome .. ??
Its particularly evident if I am flying the 38, which makes no sense I know but I cant seem to hit anything with nose mounted guns.
NikonGuy 
When it comes to hitting what you're shooting at, don't worry about lag at all.
All that matters is what
you see, on
your screen. If you can hit it, your opponents airplane will take damage; no matter what he sees on his end. It doesn't matter what your ping is, or what his is, or what they add up to be. Shoot the enemy that you see on your screen.
That's for
gunnery...
When it comes to the lag (and the difference between what you see and what he sees), that effects you (and him) in
collisions. That's different. They're not modeled the same.
Back to gunnery...
Knocking your opponent down isn't just a result of hitting him. "Lighting him up like a Christmas tree" really isn't such a great thing. That's because you need to concentrate enough rounds into a small enough section of his plane to cause failure. Sprinkling holes all over him doesn't work well (unless it's with large, exploding cannon rounds).
MG's primarily just poke holes in the other guy, and the vast majority of his plane will function just fine with holes poked in it.
So sprinkling him all over won't knock him down; it'll just poke holes in him. Do that enough, and you'll luck out and knock a control surface off, which will effect his ability to dodge your shots and will allow you to sprinkle him some more. Sprinkle him enough, and a big piece will eventually fall off... However, the number of rounds required to kill him will be quite a bit higher than the rounds required if you could hit him with all of your rounds in a concentrated spot.
It's very common for newer players (and even those with quite a bit of time) to be firing too far away, while hitting their opponent at ranges other than their convergence is set at (which is probably set out too far as well), not landing enough hits to cause catastrophic damage, and not concentrating their rounds into a small, important structural area. They will expend lots of ammo in the process, and require more (and longer-lasting) shot opportunities to be successful. That's all part of the learning process though.
It's also possible (but far less probable, IME) that you have something less-than-optimal) with your computer settings that's causing "rubber bullets". Like the other mentioned, check your V-Sync.
It'll probably help you out to fly a plane with nose guns (the 38 has great guns) and plenty of ammo. You'll also find that while the bullets will generally go where the sight is, putting your sight on the other guy will seldom result in hits, even when your opponent appears to be pretty stationary.
Practice a LOT. Go somewhere (TA or DA) where you can shoot A LOT without spending so much time flying to the flights. Concentrate on hitting your target, and taking the best shots you can set up. Get close! D200 is perfect, D400 is starting to get out there a ways... You'll still land hits out there (and even further) but they won't be as effective. Set your convergence in the 300yd range, give or take 25-50 yards. If that doesn't seem effective enough, your convergence is NOT the problem. You'll eventually hear that turning your tracers off will help. I wouldn't recommend that, but that's up to you.
