To the OP: I had a simmilar issue with a panzer a bit ago. I hit a panzer in the side from 800yds out, and he didn't die, so I turreted him. He tries to run, so I kill his engine. I drive up to 400yds, hit him twice, and get a ricochet of the center of his side armor, go to 200yds and hit him in the side, circle around and hit him in the back at point blank range twice. Never did kill him actually, he towered out after I killed the jeep brining him supps.
I must say that asside from suspected cheats, I never have problems in tanks. Even when every other player can't kill an M4 with the M4's, I can pop them at 1500yds in 2 shots. Call it what you will, but I've always had the good fortune of getting the golden BB.