I will add some of my observations, as I spend most of my time in a Gv.
It is possible even at close range to miss or deflect a shot if not placed properly
I have told people this but they don't listen, you have to have proper range. I hear them complain that they placed round after round on target to no effect, when in fact they were just bouncing/deflecting shells.
A "small" white burst means you did not penetrate with your shot. In fact if you watch closely you will sometimes see the shot deflected nearby on the ground etc.
A "larger" more pronounced white burst means you have hit it at correct range and it has penetrated.....usually one to two shots will be all it takes. If you are seeing small white bursts you are not ranged properly, it means your rounds are too far out...in effect your shell is bouncing off. If this happens you need to dial your scope back a few notches/ ie decrease range....shoot and you will make proper contact with tank downrange....this applies for close up as well.
Tigers/Panthers have thicker armor in the front and are best shot low on the side or in the rear. 1 shot in the side is all it takes to kill them. If they are facing you and you are shooting round after round....deflecting all you are doing is giving away your position and will soon be dead if they have you dialed in. The solution for this is proper flanking and popping them in the side.
I will stop there givin my gv knowledge away.
This would be a large burst from my tour in....Iraq 2003