Yup, I've gotten lots of kills in the M8, mostly against PNZR's and Osties.
75% of the battle is getting the right set up BEFORE you engage. I use AP rounds when I know I am going to be facing armored vehicles, HE rounds when I know there are thin skinned vehicles (M16, M3, PT boats, LVT's) in the area.
It takes you quite a few rounds to kill the tanks, but usually the first two rounds causes them to smoke, depending again on where you hit them. I average 12 hits per kill on tanks, nearly the same on Osties. Again, SETTING UP THE ENGAGEMENT is more important than anything else in this type fight. Clue: Hitting either a Tank or Osty in the front is wasting ammo. Get behind them!
How to do that? PM me and I will tell you how I do it............