With DOK you or any other 0 gyro angle shot you must set a range or the game won't come up with a good firing solution. The range you set isn't important but setting one is.
When using the 3 minute rule if you're using meters use 3 minutes 15 seconds to get the speed. To change to yards go to the options page and set measurement units to Authentic or Imperial.
Your hit point is based on speed, range is not important at 0 gyro angle.
When you input data always use this order Speed, AoB and last range/bearing.
Good luck and good hunting.
Magic