As a "gunwriter", I find myself using a chronograph all the time, probably more often than anybody who isn't involved in the manufacture of ammunition.
For those of you unclear on the term, a chronograph is a tool which measures the speed of the bullets exiting your firearm. This information is very useful, not only to find out if the velocities claimed by an ammunition manufacturer reflect reality but to find out what kind of performance you can expect out of a specific firearm. Generally, the shorter the barrel of a pistol, the less velocity you can expect from your ammo, but just how much of a drop you'll see (if at all) is sometimes a mystery until you actually start shooting.
Anyone who handloads, whether for competition, hunting or recreation, should be chronographing their ammo—it's the only way to find out for sure if it's doing what the loading manual says. Chronographs are easy to use—once you set up the sensors, you simply shoot over them (through the "skyscreens"). The chrono sees the bullet, measures the time it took to travel between the front sensor and the back, and translates that into a velocity readout of feet per second.
For well over a decade I have been using a chrono that was an inexpensive model to begin with. It worked, but I had to increasingly baby it. Unless lighting was perfect, I sometimes had to fire half a dozen shots to get one good velocity reading, and batteries died for no apparent reason. And then I got an Oehler 35P Chronograph.
The difference was like moving from a horse-drawn wagon to an automobile. Wow.
Maybe all modern chronographs are as advanced as the Oehler 35P, and I've just been behind the curve. Maybe I've (ironically) been too busy chronographing to look at chronographs, but the fact of the matter is the Oehler 35P chronograph is a great tool if you ever have a need or desire to chronograph your ammunition.
Oehler stopped production for a while, but as of late 2010 the 35P has been back in production and on sale. Current models are conveniently shipped in a rifle case. Not only is the case big enough to fit all the smaller parts, the three skyscreens mount on a (provided) four foot long rod, and putting everything in a rifle case is very convenient.
Setup only takes about five minutes. The skycreeen sensors are mounted on the rod, which is secured to two tripods (included). Each of the screens has its own cable, which are plugged into the chronograph which comes complete with a printer. Plug the cable from the closest screen into the Start socket, the cable from the furthest screen into the Stop socket (if you need me to tell you where to plug the middle one you probably shouldn't be around loaded guns), and you are ready to go.
After every shot you will get a digital readout and a print readout. After three, or five, or however many shots you want, you can hit the Summary button, and there's where the magic happens. You will get a printout which will show you the fastest velocity of the string, and the slowest, as well as give you the mean (average) velocity as well as the Standard Deviation. The darn thing does everything but shoot the gun for you.
I have used my Oehler now for a number of different guns (rifles, pistols, and pistol caliber carbines), in a variety of different lighting conditions, and have yet to get an erroneous reading or a round not register when passing through the skyscreens. That in itself has saved me a huge amount of time.
While the Oehler is not cheap, everything I've read and heard from other writers with more experience than me is that the Oehler 35P is the chronograph against which all others should be judged for quality and accuracy. Just about the only place I can seem to find them in stock is direct from Oehler (www.oehler-research.com), because they are in such high demand, and held in such high regard. The complete system is $575, which includes everything you need including a 9-volt battery already installed and a spare roll of paper for the printer.