How do i fire the gun?

I assume you have added in patch v1.02 ?? If not, you should, it fixes a lot of stuff. If you have the money, buy the add-on Flaming Cliffs, which is even better and is what most folks fly on-line.

In an A-10, for air-to-ground, press 7 to take you to ground attack mode. Press C for cannon range pipper. As you get closer to the target, the range scale around the pipper will decrease. Press SPACEBAR to fire the gun.

If you need to fire at other jets or helo's, press 2 for air-to-air mode. You will see a funnel shape in the HUD. For an average size aircraft target, have the targets wings touch the sides of the funnel. Press SPACEBAR to fire the gun, ENTER to fire Sidewinder air-to-air missile.

THANKS