Remember, BC is most directly described as the ability of the bullet to retain velocity. So, the most direct way to measure BC is to measure the initial velocity and the downrange velocity. Sounds easy enough to do with commercial chronographs, until you consider the realities and sensitivities of the test. To get the most accurate measure of velocity retention, you need to place the chronographs as far apart as possible so that any error in the chronographs is small compared to the total velocity lost. However, the farther apart you place the chronographs, the harder it is to shoot through them because they’re designed to be set up at the muzzle and have a narrow field. It’s pretty easy to shoot through a chronograph at 200 yards, but at that close of a distance, your measurement is highly subject to error. Additionally, you’ll only be measuring the BC at high speed and not the overall average for long range flight. If you place the chronograph at a long range, like 1000 yards, it’s very difficult to shoot through the narrow window. As you can see, measuring velocity retention directly with chronographs is very difficult, but we’ll come back to it later.