Here's a tip if you are using the T34/85 sight. If your target is a Panzer and he is broadside to your view and the length of his hull is the same distance as between two ^ marks then he is exactly 800 yds out. If the length is ^ to : then he is 1600 yds out. If he spans two ^ (i.e. ^ : ^ : ^ ) then he is 400 yds. Everything scales inversely, i.e. if it spans twice the view it's half the distance. Other tanks are about the same length and therefore about the same range, although the Tigers are a bit longer so they will span a bit more of your reticle at the same range.
If the Panzer is facing you everything is halved, ie if he spans two ^ then he is 400.
Now, if the Panzer is moving and is broadside, then lead him by two ^ marks if he has accelerated to full speed.* If the target is a T34 lead by a bit more than two ^ because he's faster than a Panzer. If it's faster still, like an M3 or M18 then lead considerably more.
Obviously it helps if you have a high resolution screen to be able to judge the range. At very long range, like beyond 2500 yds try going by other clues, like if a friendly plane marks the target look at his icon and get the range from that. When adjusting range don't try to "sneak up" in small increments. Use a mathematical technique similar to Newton Raphson, if the first round is short make sure you add enough range to make the next one long then start cutting the differentials in half to zero in on the target.
*this is for AP, lead a bit less for HVAP since it's faster. But don't use HVAP beyond 1200 yds as it slows down more than AP and is therefore not as useful beyond 1200.
