This article was not written by me. Two young men won first place in the Physics and Astronomy division at the 2008 California Science and Engineering Fair. They wrote this up, and I asked Pyramyd Air to publish their findings. These boys have done an outstanding job of showing the effects of air pressure on velocity.
While this shows the use of the Shooting Chrony, the basics of using a chronograph are the same across the board. Airgunners use chronographs a lot more than firearms shooters. Even if I weren't a writer, I would get a chronograph so I could pick the right fill level for my precharged pneumatic guns, select the best pellets for any gun and to make sure my gun is in top operating order. Read to find out all the things you've been misssing without a chronograph!
It's easier to load round balls (and we're talking about round LEAD balls, not steel BBs) since orientation doesn't matter. But are there other advantages or some disadvantages? This article gives you the straight scoop.