Well I went into the TA and practiced some. A single AP shell with take out ack but it has to be right on.
I've found that when on level ground with the ack you have practically zero depth perception as to where your shells are landing (even at max zoom). And, as a rule of thumnb, if they're shooting at me then I'm in range to shoot at them. For GVs which are on the surface you can tell if your shots are too far or too near by whether the explosion is in front or behind the vehicle and adjust accordingly. However, with most ack, they are nearly buried in the ground so you can barely see them if at all.
So, the best attack I've found is to stay fairly far away (i.e. they haven't started firing yet) and use the AP shells to pick them off one at a time. I de-acked an entire field that way the other night. More importantly, if at all possible, look to get elevated above the field you're attacking like on a ridgeline or hill to better spot where the shells land to adjust your gun elevation.
