the firing animation is a good start, but it does have a few flaws i would like to point out =P.
-if this thing is going to have an idle animation, it needs to go from idle to shot while still in idle. you don't turn off the tank to fire the cannon.
-recoil. when you shoot a rifle, you feel recoil from the gun. i know this, as when i shot a rifle for the first time, i accidentally dropped the gun because i didn't have a tight enough grip. the back of the tank should jut backwards, if only by one or two pixels.
-the smoke needs some serious work in my oppinion. it just kinda floats up. not sure how a tank works, but i think it would flow a bit better if little chunks burst from the black and white flash (which i do like), and sorta deteriorated into mid air.