Air to Air: The Gun Kill

Ok, you've manoeuvered to the MiG's 6 o'clock and you're ready to take him out.
At this point things will be happening very fast, so you need to know when to let rip. You will see something like this:

Good job, young Jedi!
Even if you have a radar lock the Gun Pipper will probably be bouncing around a lot, and therefore will not be much help in aiming.

The FDI (Fuselage Datum Indicator) is pointing ahead of the MiG:

But I'm pulling nearly 3G so the shells will fall somewhere behind the FDI.

You won't have time to look at the G meter, but with a bit of practice you should be able to tell the G-load by the deflection of your joystick.
Unfortunately the gun discrete lets us know that there are zero shells left.