This review was on the Midway page for the CED. You might try this.
" Hi I don't have one of these chronographs, but I do have a chronograph of another brand. I notice that a lot of the people writing negative reviews of this product say it's very finicky in bright sunlight. My chronograph instructions said that on bright days the light reflected from the ground can keep the bullet from casting a shadow, which is what the sensor detects to start and stop the timer. The instructions for mine said to avoid this by blackening the bullet in from of the casing. I keep a black Magic Marker in my chronograph case for this. I live in Wisconsin and sunny days in winter would have a similar result with error readings or no reading at all without the blacking of the bullet. With the coloring of the bullet the problem is completely or nearly completely solved."