First the code does not have a voltage drop "rule". This information appears in a fine print note and is not an enforcable rule. Second, if you have a measurable voltage drop without a load you have serious wiring problems. The only way to test for a voltage drop is to use some type of known load. You must remember that when you are using a voltage drop tester you are measuring the voltage drop all the way from the utility transformer and not just on the branch circuit.
Don
